These wonderfull plans are all but useless for us that use the metric system.

1" = 25.4mm. Quite easy and makes the plans quite useful.

Dan

if you have the drawing files then just change units to metric... then diminsion them, if not then use a converter...

I'm in Texas and will use dec. inches, sorry, thats just the way it is here, and if you have someone who can do drawings in metric, then have them do it... for goodness sake they are free, someone has done the hard work for you, what else do you want... lol :D

Heavy,

JGRO has provided us with a great set of plans for an entry level CNC machine, for FREE. I'm sure that John used Imperial units because that is what he is most comfortable using and matched the materials he was able to purchase locally.

What is great about the plans is that you can follow them exactly and wind up with a fantastic little machine. Or, you can tweak them to make them work with the components available to you. You can scale it larger or smaller, reinforce it, use higher quality components, or even (dare I say it) convert it to Metric units.

The plans are just a rough guide. John has done the hard part and come up with the design and provided the plans in AutoCAD, SolidWorks and Catia formats so that they can be modified. You can open the parts files in SolidWorks and with a few clicks all of the dimensions can be converted to Metric units. The dimensions can then be rounded or modified to match materials available in your locale. Plus, it's good practice to do the conversion/modification if you need experience with whatever CAD program your going to use. Barring that, there is always the pencil and calculator conversion method. Given the original JGRO design along with a little time and patience, it should be fairly easy to do the Imperial to Metric conversion.

Take the initiative, then you can post the JGRO - METRIC version.

You can make it work,

HayTay

Please God, don't let the US go off the imperial system, else I must retool.

I've always found imperial machines to provide the utmost in function and utility, its those darn metric ones that are useless :D

I do see the point though that if only metric threads/bar stock is available, it's not as simple as multiplying by 25.4 - but HayTay is right on, someone who's provided free plans has done his part (wish all hobbyist had that attitude of wanting to help each other for the sake of helping) so don’t complain, step up

Metric is the best! Yeah, I'm from the US! :)

Was not realy directed at JGRO more in general to everyone. But JGRO's plans will be a good reference.

And note that:
"Don't give me the excuse "it's free, so stop complaining"; Garbage is free but you don't jump in a landfill do ya". -- Some Poster at slashdot.org

I always hear how metric is eaiser to use than imperial. Imperial is to confusing with all those fractions and such.

Does that mean that those of us that use imperial are inherently smarter than metric users ?

"Abestos suit on"

I'd guess that almost anyone who has dimensioned plans posted would be happy to rework them in metric if you offered to pay them for the effort of accomodating you ;)

"anything free is worth exactly what you paid for it"... if you want it to be other than the free version, it's reasonable to expect to pay.


Tiger

I built the JGRO in its imperial units and had no problem although we are officially metric. Get an imperial tape and rule or convert the units to metric, its not that hard.
Funny enough its easier to convert some of the hole diameters to mm than to get them to 1/16 or 1/32 fractions.

As Hack posted 1 inch = 25.4mm
You do not need any other info.

In some cases metric is easier to use than imperial, however for physically building a project I opt for imperial. When drawing objects in CAD both for my CNC machine and otherwise I opt for metric.

Jason

"Garbage is free but you don't jump in a landfill do ya"
whats the ol saying one mans trash another mans treasure

Question: what do the Japanese call a handicapped individual who only can speak one language???

Answer: an American.

Does that mean that we need to start calling anyone who can't work in Imperial and Metric units "a European"???

I'm not that arrogant but really......

Having been in the US engineering community for longer than I care to admit, I"ve had to learn to work in EITHER units although I prefer Imperial. IN fact right now, I'm working on a component for a German company who's making a Brazilian intended part by an American prototyping company. I have to design the turning in metric (the oem drawing is metric) BUT I have to supply the drawing to a turning shop in Imperial units. That's life in a global economy.

Sadly, the "globalization" of out educational system is forcing the U.S. kids these days to work in Metric units. Can't tell you how many engineers just out of college anymore CAN"T work in Imperial units. It is truly sad... Some call it globalization, I call it "dumbing down"...

Too bad as the world is in the process of eating away at out economy and ultimately our livelihoods. Knowledge, training and the uniqueness of our measuring system is/was a last bastion of defense against ALL our technologies being summarily shipped to a low bid, Nth world country because they can/will do it cheaper.

I fear that we're living in the denouemont of our society. Will the last one who leaves, please turn out the lights....

Meanwhile, my CAD system will easily convert from English to metric dimensions with 2 key strokes - and it is nearly 10 years old. If yours can't, I'd say you got ripped off.

If you can't even convert from english to metric with CAD files, as the message thread title implies "for god sake, use meterics AND design your own.....". (chair)

Metric, is still better! :)

These wonderfull plans are all but useless for us that use the metric system.

When all the materials used to build it are in imperial units, as are tape measure, and virtually all woodworking measuring devices in the US, metric doesn't make much sense.

I use metric. It isn't "better" or "worse" than imperial, it's just different. I prefer it to imperial and I'm comfortable with it. In the U.S., most people seem to use imperial for the same reasons. We have different opinions.......SO WHAT!!!

These wonderfull plans are all but useless for us that use the metric system.

I, for one, feel that this thread is not at all appropriate and would ask that you perhaps re-phrase. I find it offensive and extremely rude to those whom have shared their work.

If someone gives you an automobile for free would you complain if the tank wasn't full of fuel?

Re-design the thing yourself. Don't come here and complain that someone did not consider your handicap when he posted the plans free of charge.

Sorry - I had to vent.

Scott

I god had meant us to us the metric system, we would have been born with ten fingers :)

I god had meant us to us the metric system, we would have been born with ten fingers :)

That's a good one!

As my previous, Austrian employer would always say - "there are 24 hours in a day. If we can not finish in that time then we must work overtime."

You Austrian guys are comical!

:cheers:

Scott

I god had meant us to us the metric system, we would have been born with ten fingers :)


Dear Mark,

The problem is that I've got eight fingers AND two thumbs. As a result, I still can't figure out what HE intends us to use.

Regards

Martin

---
Make thee an ark of gopher wood; rooms shalt thou make in the ark, and shalt pitch it within and without with pitch. And this is the fashion which thou shalt make it of: The length of the ark shall be three hundred cubits, the breadth of it fifty cubits, and the height of it thirty cubits. A window shalt thou make to the ark, and in a cubit shalt thou finish it above; and the door of the ark shalt thou set in the side thereof; with lower, second, and third stories shalt thou make it.
---

Of course we can continue the argument of whether to use milli cubits or 1/4, 1/8, 1/16, ... cubits.

Ken

---
Make thee an ark of gopher wood; rooms shalt thou make in the ark, and shalt pitch it within and without with pitch. And this is the fashion which thou shalt make it of: The length of the ark shall be three hundred cubits, the breadth of it fifty cubits, and the height of it thirty cubits. A window shalt thou make to the ark, and in a cubit shalt thou finish it above; and the door of the ark shalt thou set in the side thereof; with lower, second, and third stories shalt thou make it.
---

Of course we can continue the argument of whether to use milli cubits or 1/4, 1/8, 1/16, ... cubits.

Ken

Dear Kenneth,

The obvious solution to my problem is to work in a combination of octal and binary. I'll be searching my tool store for the required vernier.

Best wishes,

Martin

"A cubit is a unit of linear measure, from the elbow to the tip of the longest finger of a man. This unit is commonly converted to 0.46 meters or 18 inches, although that varies with height of the man doing the measurement. There is also a “long” cubit that is longer than a regular cubit by a handbreadth."

The NBA cubit is somewhat longer than most! :p

"A cubit is a unit of linear measure, from the elbow to the tip of the longest finger of a man. This unit is commonly converted to 0.46 meters or 18 inches."

0.46 meters or 18 inches?

This proves God was behind the imperial system. :)

I might be shooting myself in the 304.8mm but I'm willing to bet Heavy didn't mean it a harsh way. I thought it was funny, actually. I can picture the guy going through the measurements and thinking "what in the world is 3 inches in real money"? I went through something similar in engineering school when everyone started talking metric. I use imperial.

JR

even today, when all our hardware is made in Taiwan and China, it's a pain to use metric here in the U.S. When McMaster-Carr starts charging a premium for Imperial hardware, I'll probably be brave enough to switch. At work, I buy Metric if it's reasonable, it's pretty tough to find American grad students in engineering, particularly after my boss gets done explaining all the math courses he wants them to take.

I might be shooting myself in the 304.8mm

JR
Now tha't funny! :)

I think everyone here has kept the humor in this, now let's just hope Heavy understands our humor! Actually what he says makes sense, especially when I have to look at a set of prints that are in metric. It would be nice to see them done correctly! :D

Mike

I wish that metric had won out long ago, but it didn’t. We have two systems and we have to get over it and be able to talk both. I talk both at work everyday. Sorry, reality gets in the way.

Thank God that there is no metric time, or the transportation system would be a real mess with a 10 hour clock.

Steve

[QUOTE=spalm]....Thank God that there is no metric time, ...../QUOTE]

The people responsible for the whole idea of metric measure tried it but it did not catch on. I guess nobody had the time for new ideas about time.

Next someone will post why it wasn't done in French?

Didn't we lose a probe to mars because the engineers who worked on it were using imperial AND metric... something got mixed up if I remember right.

I work with both and don't have a problem- the only thing that's difficult to convert is aspheric co-efficients.

The formula I use for the sag (Z) at a specified departure from centre (H) is:

Z=((CURV)H^2)/1+(1-(1+K)(CURV)^2 H^2)^1/2 +(A)H^4 +(B)H^6 +(D)H^10

Converting the Aspheric Coeficients is a bit tricky so I tend to chuck the drawing back to the designer (after contract acceptance of course!) and ask for a conversion. They usualy don't mind.

Didn't we lose a probe to mars because the engineers who worked on it were using imperial AND metric... something got mixed up if I remember right....

A potentially more serious metric mixup was the case of the Gimli Glider; a 767 that was not refuelled correctly for a flight from Toronto to Vancouver. It ran out of fuel halfway there over the Canadian prairies and the pilot brought it down successfully to an unused airbase; gliding from 35,000 feet.

Those things don't have fuel gauges??????????????????????????????

Some of us are in a worse position with this than others. I'm a violin maker who also makes guitars. The violin makers I know all use metric, the guitar makers I know all use imperial.

Makes it hard when your talking to a mixed group. But you adapt.

I started out in Imperial in Automotive machining then went to Metric machine tool building. Now, everything I do is designed in MM and is dual dimensioned for the 'Milliterate'. I still have to design around English sized materials, though.

I think it is wise to be able to visiualize and utilize both and I would be willing to bet that most of the folks on this board can do just that.

Scott

One Question:

so.....What size is a "Two - By - Four" in Europe anyway?

and: (The Existentialist in me can't resist)

If there's a "Two - By - Four", but nobody's there to measure it.....Is it really a "Two - By - Four"?

If there's a "Two - By - Four", but nobody's there to measure it.....Is it really a "Two - By - Four"?

It's only a 2 x 4 till you measure it!

It's only a 2 x 4 till you measure it!
Then it becomes a 1 1/2 by 3 1/2. :)

The irony is, that imperial stems from European measurements taken from a kings foot size, and other odd places. While the Europeans have since taken on the French system of metric, it seems that the much of the USA public is reluctant to get rid of all its ties to the mother land, even if the mother land iteslf has.

The other irony is when you go to install software you get the option to install it with US English or International English. This implies that British English is in the same catagory with the impure international English, and only the Americans know how to really speak English. :)

But of course we Americans speak english -- the Brittons speak British! ;)

-- Chuck Knight

Both systems are arbitrary units of measurement no matter where they come from.

One system is just easier to teach. But we here on this forum already know our own respective systems. So there is really no use in arguing someone else’s way of doing it.

The real pain is conversion and neither system is any easier in this respect.

As technology progresses it will slowly change to metric and that is a shame because then we wouldn't be able to argue about how annoying the other is! :D

These wonderfull plans are all but useless for us that use the metric system.

I think the above statement is quite a good indicator of the best metric has to offer. It reallly seems more of an international attemp at dumbing down the entire world. I can't imagine anyone that normally uses the imperial system not being able to convert plans from metric and put them to good use.

I can't imagine anyone that normally uses the imperial system not being able to convert plans from metric and put them to good use.


I 'm pretty sure that most people using metric can convert plans in the other direction. (Except Heavy. Are you sure he isn't just trying to get an indignant reaction for the hell of it?)

Theres one thing for sure and that is, It got a reaction.

Bill s. (Yorkshire Man, English Man and I guess European)

All kidding aside, I for one don't think that one is system is better or worse than the other, and though I have a preference for the one I learned first, I'm comfortable using both.

It could be that there are disciplines that are better served by one system or the other. For example, in the physics class I recently took, all the equations turned out to be much more elegent when using the metric system. Not that they couldn't be done using imperial, because I did them both ways. In the end I had to admit that metric was better suited to this purpose.

I can't help but think that there are some political roots to these arguments. Those who don't live in the U.S. won't have heard of this, and the young people who do live in the U.S. won't either. But this should jar a few old timers. In the U.S. we used to have two common standards for bolt threads. There was SAE which was the finer thread of the two, and there was USS (Nicknamed "Standard") which was the coarser thread of the two. You could walk into any hardware store say you wanted a half inch standard or a half inch SAE and get what you wanted.

Then the politicians got involved.

The U.S. congress (Yes our senate and house) decided to abandon these standards and come up with a new standard. The fine thread is now called UNF (for Unified National Fine) and the coarse thread is now called UNC (for Unified National Coarse). Now, they didn't change anything but the names. All the dimmensions, thread counts, and geometrys stayed the same!

They are the EXACT same bolts but now with a DIFFERENT NAME!

So now I have taps and dies downstairs in my shop that are marked using different naming systems. How much do you figure THAT cost heavy industry?

So how many think there is some politics behind the whole Metric/Imperial debate?

If you think standards of lengths are a pain have a look at the history of the Gallon.
http://en.wikipedia.org/wiki/Gallon
The 13 or more different "standard" gallons makes the reason most of the world converted to metric self explanitory.

i live in canada lots of things are in metric here but so many drawings are still imperial
and when they aren t i pull out the calculator and convert it ,metric sucks

i live in canada lots of things are in metric here but so many drawings are still imperial
and when they aren t i pull out the calculator and convert it ,metric sucks
Conversion sucks. Working in one standard, whatever it is, will always seem better.

Conversion sucks. Working in one standard, whatever it is, will always seem better.
agreed

Question: What do they call a machinist who can't work in both metric AND imperial units?

Answer: Poorly educated.

I learned many years ago that life's problems aren't always evenly divisible by 2 and that the quotient isn't always going to be an integer.

I can understand why folks feel more comfortable working in one unit or the other but this is a global society anymore - learn how to adapt or else live in your own little world and find happiness in *****ing.

There are some autoworkers in the USA who are going to be in that situation soon, sadly, and surely they'd happily build cars using either metric or imperial units - just as long as they had cars to build, which may not be the case for long.

Because I grew up in a country that changed to metric only in the 60's (New Zealand) I grew up with a Dad refering to everything in feet, inchs, thou (he is a boilermaker) and miles.

School was all metric, but the conversions were well covered.

Got into aviation engineering so I have mostly worked in the imperial system. My hobby machining is mostly metric.

Having a good feel for both, I wonder whether there is a subtle quality difference created by being completely immersed in one system.

A thou was a very usable measurement in the days of manual work and manual tools. You can feel the difference of a thou. It is a good standard of tolerance with a file. 1/100mm is too fine a tolerance for cost effective use in general machining.

I wonder whether the german reputation for quality was subtle influenced by all those tradesmens in the fifties making things to 1/100mm rather competing in a market with english and US products built to a thou? Maybe that early Jap crap reputation for asian products of the seventies was built on manufacturing to 1/10mm?

Question: What do they call a machinist who can't work in both metric AND imperial units?

Answer: Poorly educated.


No, just stubborn.

Question: What do they call a machinist who can't work in both metric AND imperial units?

Answer: Poorly educated.

So your poorly educated?

Man and I thought some of the advice you gave on bearings was top notch to! :D


Realy though, you need to work on the delivery though or maybe just the joke, its not really funny.

Question: What do they call a machinist who can't work in both metric AND imperial units?

Answer: inch-inist

I know, I know, cheesy too.

JR

Those things don't have fuel gauges??????????????????????????????

Thats Funny :)

Who woulda thunked? :idea:

.

Sorry you got the wrong impression, Miljnor, but I work in both systems although I prefer Imperial as that was the first one I learned.

Bearings are globally metric even though most ball sizing is still Imperial (go figure) - had no choice but to adapt and feel I did so well.

The US auto industry was mostly imperial. Now it is mixed mode. The racing stuff I do is mostly in inches, the OEM proto stuff is mostly metric.

As I deal with both US and off-shore car companies with my prototype business, I have to work in both and have to tailor my replies to the education level/units preference of my customer.

Most meetings start out with "Hi, I'm so and so - what units do you prefer to work in???" Fun to see the blank stares on young engineers faces when the old man works in either unit and they can't.

The "joke" was a true adaptation of how the Japanese feel toward Americans behind the scenes. The original "joke" is as follows;

Q: What do you call an ignorant individual who only speaks one language?

A: An American....

Might not be funny but that's how we're perceived. Sadly, the truth sometimes hurts....

You'd be AMAZED at how many engineers coming out of high buck, high profile BIG 10 colleges CAN'T work in anything but metrics. Tis truly sad.... Like I said, "...poorly educated...." which is NOT stupid.

Knowlege is power. Sieze as much as you can or else sit there and curse the darkness as your competition passes you bye...

What do you call a person who can't do arithmetic in their head?

Poorly educated.

The metric system is perfect for them.

I find it amusing that the post which started this thread is entitled "For the love of G-d use metric" when metric measurement, deliberately not human-scale, is the last holdout from the anti-religious French Reign of Terror.

i guess this is kinda touchy, lots of opinions and everyone has one but doesn't really make one better then the other... just be thankful everyone is sticking to a base 10 for the numbers wouldn't you love seeing it in hex or oct or something? :rolleyes:

Thats Funny :)

Who woulda thunked? :idea:

.

Hello Switcher,

I've now read the story of the Gimli Glider

http://www.wadenelson.com/gimli.html


Yes, they do have fuel gauges.

Yes, they took off knowing that the gauges were out of action.

Thank heavens that their airmanship was better than their skills at calculation.

Martin

Does it upset you metric users that your metric socket wrench has a 1/4" drive? :)

(can you get a metric size drive for a socket wrench?)

Does it upset you metric users that your metric socket wrench has a 1/4" drive? :)



I wouldn't know. Mine is 6.35 mm.

Martin

Sorry NC I misread the quote. Its actually funnier now that I noticed the 't . Next time I will pay more attention.


I was wondering why the joke wasn't funny and then I read your reply, thinking: "man this guy is insane!" of course giving the benifit of the doubt, I re-read your joke. Then said, "well maybe the insanity is on my side!" :D And realy, since there is no one here but me, I am now talking to myself! (nuts)

:cheers:

I wouldn't know. Mine is 6.35 mm.

Martin

I call that soft metric. Do you have a hard metric drive?
Bill

Thank goodness for the English (re the 6.35mm drives0.

They gave us Americans our language,

BUT

The Americans gave it character and personality...

In return, the Americans figured out how to make beer cold (the same people who make Lucas ignitions systems which were notoriously lame supposedly made refridgerators).

I'd say we're even.....

I call that soft metric. Do you have a hard metric drive?
Bill

Yes, we have two. They are 9.525 mm, and 12.7 mm.

Regards

Martin

Hello Switcher,

I've now read the story of the Gimli Glider

http://www.wadenelson.com/gimli.html


Yes, they do have fuel gauges.

Yes, they took off knowing that the gauges were out of action.

Thank heavens that their airmanship was better than their skills at calculation.

Martin

I think the pilot earned a commendation for his skill and a suspension for the fact that the lack of fuel was ultimately his responsibility.

Thank goodness for the English (re the 6.35mm drives0.

They gave us Americans our language,

BUT

The Americans gave it character and personality...
....

If you look into the etymology of many of the differences between American english and English english the American versions are holdovers from two cenuries ago or so while the English has evolved over time. I would never make the interpretation from this that Americans are conservative, stodgy stick-in-the-muds.

Yes, we have two. They are 9.525 mm, and 12.7 mm.


And I thought the main benefit of metric was to not have to work with difficult things like 1/4, 3/8 and 1/2.

And I thought the main benefit of metric was to not have to work with difficult things like 1/4, 3/8 and 1/2.


We don't have any difficulty with 1/4, 3/8 and 1/2. We call them soft metric.

Regards

Martin

There's a difference between saying "I can't" and "I've never done that before". Anyone with half a brain can take the time to convert from inches to mm and vice-versa. Therein lies the problem - taking the TIME to learn something new and ADAPT.

BTW - NC Cams: I used both imperial and metric at the "high buck, high profile BIG 10 college" I attended. :)

The "intelligencia" in college tended to use the metric stuff as it was more "global", hence more intellectual. Can't wait until some PHD froma third world country takes away their job at 1/10th the salary. They'll be sorry that they were so supportive of a "global standard" that, ultimately and effectively, enables management to export jobs to lower cost producers...

The kids who were racers at heart and worked on small block Chevy's prior to and during colleg usually knew metric and english and could smoke the metric crowd when it came Formula SAE and the like. They also tended to run raster in sporty car racing because they knew the words, music and synergy of fast cars and loose women (but that's another story altogether).

If you can make horsepower and know the theory of engines, it don't matter if it is metric or American. The principles are all the same. Knowledge is power and that's the important thing to gain...

Goodness me, I used metric in college, although up here we call it university. So I suppose I am one of the intelligencia. Never been described as one of those before; I wonder whether it is an insult or a compliment.

I remember being told by a snooty northern european that the US would HAVE to convert to metric or be left behind the rest of the world! That was 30 years ago and I don't feel left behind in the least.

IMO, for anyone with a firm grasp of the imperial system adding metric is a no-brainer. It appears from this thread that the opposite is far from true.

I used metric in college, thirty some years ago. We dealt in grams and kilos, but it had nothing to do with being intelligentsia, or even to do with classwork.

Kilos? you must have been very rich college kids.

Kilos? you must have been very rich college kids.

Grams and kilos was my first introduction to the metric system, but it was in high school in El Paso. Guess I was an early learner.

The US money system is based in units of ten. The metric system is based in units of 10.

How many shillings are there in a pence?

Which weighs more: 1 kg of feathers or 2.2 lbs of bricks?

Kilos? you must have been very rich college kids.

Ummm...:)...:wee:

.

If all you can work in is metric (or imperial), then "intelligencia" is clearly NOT a compliment.

The college kids I was referring to were pretty snooty as they graduated from a noted Big 10 engineering school. Yet, they couldn't deal with imperial units. Clear case of poor education if you ask me....

Please refer to prior posts 49 & 55 for clarification.

Reply to post 77:

1 kg of feathers by roughly 1.816 grams.

Reason: 1kg = 2.204lbs

Posts 49 and 55 are herein restated by reference....

I think the pilot earned a commendation for his skill and a suspension for the fact that the lack of fuel was ultimately his responsibility.


Dear Geof,

I didn't mean to be harsh on them to make a cheap point on the metric debate. We all make loads of mistakes. Those people have my enduring respect and admiration. Utterly fantastic airmanship.

Best wishes

Martin

The Gimli Glider did not get into trouble because of metric measure or because of Imperial measure. They could have fueled up in glugs and splashes, as long as everyone agreed on what was to be used. One could, in fact, place the blame on the mandate to change the system of measurement used.

The college kids I was referring to were pretty snooty as they graduated from a noted Big 10 engineering school. Yet, they couldn't deal with imperial units. Clear case of poor education if you ask me....
Please tell me it wasn't Penn State. I keep thinking I want to teach, maybe if I do one of the lesson plans will be not being snooty. Nothing stupider than an engineer that assumes they know more about something than everyone else. If I have a problem, it's the fact that I try to learn as much as I can from everyone I meet.

Reminds me of an old joke though. When you get your B.S. degree, you think you know everything, when you get your M.S. degree, you realize you know nothing, and when you get your Ph.D., you realize your advisor knows nothing.

.Reminds me of an old joke though. When you get your B.S. degree, you think you know everything, when you get your M.S. degree, you realize you know nothing, and when you get your Ph.D., you realize your advisor knows nothing.

There are a couple more versions:

B.S. (B******t)degree, MS (more****) degree, Ph.D., piled higher and deeper.

Or; as someone goes through the degrees they learn more and more about less and less until a Ph.D knows everything about nothing.

Reply to post 77:

1 kg of feathers by roughly 1.816 grams.

Reason: 1kg = 2.204lbs

Posts 49 and 55 are herein restated by reference....


I'll try to be more careful with my significant figures the next time I make a joke. Just trying to keep it light-hearted.

I didn't look at the feather/brick deal as not being a joke but more of a trick question.

Sort of like the pound of feathers/pound of gold comparison. (a pound of gold weighs more as one is in troy and the other is in avoirdupois or some other fancy word I can't spell).

BTW. it wasn't Penn State, it was U of M. Snooty engineering grad who couldn't do the simplest of conversions. If you're gonna preen, be prepared to shine, especially when it comes to mundane technical minutae, especially if you graduate from a prominent school that your parents paid a ton for your to go to.

I'd like to quote Dave Barry...

"In 1975, the President asked for a 10-year voluntary American transition to the Metric System. This transition began with the DOT putting up metric highway signs. Americans responded in true American fashion: By shooting holes in them."

It's just numbers, gang.
If 'American' measurements are so great, then
What's up with drill sizes "1" through "80" and "A" through "Z"?
Why is a #4 drill not the same diameter as a 4-40 thread?
We buy 2-liters (or litres) of soda,
9mm guns

And as for the metric system... The Gimli Glider, as well as (afaik) all other airplanes, measure altitude in feet.

It's just numbers... in my shop, we have an abundant supply of digital mics and calipers that can switch to measure in either units.
Our comparators also can switch back and forth effortlessly.

Whether it's inches or meters (or metres), it's pretty straightforward... the thing's in tolerance, or it's not.

The only problem I've ever seen is when a metric part has been programmed in inches (or vise-versa), and the operator has to change an offset in different units.

But calculators tend to put an end to the confusion!

"Glugs and splashes"... I wet my pants I laughed so hard!

Was in an intesting meeting the other day.

The sales engineer made a snide remark during a meeting and showed clear disdain when I mentioned a diametral spec in inches. He clearly let it be known that I was working with a metric company.

So, to prove a point, you should have seen the look on his face when I immediately appologized and converted it to the exact figure in microns on the spot, and without a calculator.

Trick was, I was explaining the drawing to the machine shop foreman who I knew worked in inches and preferred it that way - the conversion was done for the S/E as he clearyly wasn't capable of working in dual dimensions.

After that performance the guy sate there (after the immediate metric conversion) and didn't utter a peep thereafter. By the way, I got the job on the spot for that and a couple of other reasons.

Ultimately, you have to satisfy your audience PERIOD. When you can demonstrate an ability to do that, you'd be amazed at the advantages you can create for yourself...

Don't curse the unit of measure - embrace and learn it. Can pay off hand$omely if/when you do....

Slugs vs newtons vs psi still bother P/O me but that's what they make converting calculators for.....

EVERYTHING I put out is dual dimensioned - even if it is for use in my own shop. This keeps the complaining and excuses to a minimum.

But - I put the metric on top!

It is funny too see people's reaction when you have the ability to convert microns to mils w/o a calculator! Most folks think that you are just trying to be smart a$$...

Scott

that would just give them one more excuse to call me a smartass!

Good thing I cant convert in my head!

It seams the further away the calculators are the better and faster my brain seems to do math problems! ;)

Its a subconscious thing, but, If I can see a calculator my brain won't do the math. (chair)

Brain cells shouldn't be allowed to form unions! :D

:cheers:

Brain cells shouldn't be allowed to form unions! :D

:cheers:
if they could mine would be on strike!!

Scott:

A smart a$$ only THINKS he has all the answers whereas a crafty old ba$tard already HAS or can readily CALCULATE the answers.

Treachery and old age will always triumph over youth and enthusiasm. The kids don't realize that in most case, we've already been there and done that and ruined the T-shirt learning how to do it properly.....

Scott:

A smart a$$ only THINKS he has all the answers whereas a crafty old ba$tard already HAS or can readily CALCULATE the answers.

Treachery and old age will always triumph over youth and enthusiasm. The kids don't realize that in most case, we've already been there and done that and ruined the T-shirt learning how to do it properly.....


....And the old ba$ters can't see that the rules to the game have changed and are not the same any more!! We use software not not our fingers

I am of the odd age - went through school w/o computers but by the time I emerged into the workforce, it was expected that one be proficient with computers. Folks 5 years younger than I were not required to take mechanical drafting using pencils and erasers, don't know what it's like to have to wait 20 minutes to re-heat leftovers and have never actually had the pleasure of watching a tin of Jiffy-Pop expand!

Scott

In my case, I created the company, make my own rules and do use a computer as well as my fingers - lost too many good paying jobs by not playing to someone elses lame a$$ rules which were quite vacuous in my opinion.

Although I got to hand it to them for trying, the kids do challenge me but at best they can equal me so far - but they're gaining fast.

It would be nice to mentor a couple and gain their respect so that, someday, they'll say they learned something from me cuz the old geezer was pretty sharp....

Besides, maybe they'll take an interest in the operation and buy it to carry on. Not having had any kids, that's the best I can hope for cuz the government will tax the remnants to pieces when I try die and try to give it away...

Regarding use of computers instead of fingers - try using one in a pop quiz job interview when you don't have a computer or calculator handy or when the battery is dead and/or you don't have power...

Last job interview they popped that on me (tech test) to try to sort me out. Turns out I was the only person in the history of the test to get ALL the questions answered correctly and calc'd properly and did so w/o a 'puter.... the job offer was on the answer machine before I even got home.

Thank goodness it was math based stress calcs on the test as opposed to calc or trig which I can't do without the book. Sometimes it is simply better to be lucky than good....

the first question I like to ask a kid is what does 4Xsfm/ dia.=(rpm) you would be surpised at some of the answers I get

Scott: today's Jiffy Pop comes in a paper bag with metallic foil imbedded in the wall instead of surrounding the product. Uses microwave instead of range/stove. Same principal/effect, faster performance. The swelling aluminum top on J-P was fun to watch however... much more so than the watchin the bag swell.

I entered the engineering work force a couple years before the Apple II took off. Learned drafting with pencil and paper however came across a neat parametric CAD program in early 90's called DesignView that readily replaces mechanical drafting. Does sections if you draw them ala pen and paper but doesn't do hidden lines well. Otherwise it is FAR superior to pencil and paper, especially the parametric part.

Sadly, Computervision who made it has been swallowed up by ProE and the "replacements" are not as simple to use, need much more of a PC and are way more complex than need be for many simple design tasks.

Sadly, the program isn't sold/supported but it is REAL easy for even us old timers to learn. The early version runs on Win3.11. I got hold of a "new" version from a guy in S. Africa on the net that works on 3.11, 95 & 98 and even ME. Haven't tried it on anything past ME but it should work.

Lakeside: I'm missing something as its been a long sleepless night.

Don't you have to know cutter diameter and isn't pi figured into your trick question some how???? Or is that just a quickie calc???

it could be cutter dia. for a mill or stock dia. for lathe just quick cal. for ballpark rpm lot faster than using pi
for software I like ME Pro it about $100 and you can customise it for any materail here a link(no I don't sell it but think it's worth the cost) and it uses metric too!!
http://www.mrainey.freeservers.com/

Living in the UK and being an old git (44 Year old...) I was at school just as the UK was changing over to Metric, so I had to learn both standards.
I go down the Pub, and buy a Pint of Beer, not .5675 of a Litre......
I fill my car up with 25 Litres of Petrol (Gasoline) not 5.5 Gallons (Imperial)
If I see a Plane flying by my house, I guess its altitude is about 1500 feet and not 457.2 Metres....... (I Live near an Airport!)
if I give someone directions, I say "go down this road 200 Yards" not 152.4 Metres......
etc etc.....
Being an Engineer, I have to be familar with both systems, both are good, use the one you are familar with.
I am toying with building a CNC Router, and I really appreciate the time and effort the US guys have put into creating the plans.
I load the DXF files into my CAD Software (US Program!!), and I press one button to convert it into metric.

If someone says it measures "1 and 5/8 Inches" get your calculator out,

5 divided by 8 = 0.625 Plus the One Inch = 1.625"

1.625" x 25.4 = 41.275mm

Its not rocket science.

Cheers

Andy

Well said Andy.

Jason

Andy - old git ???? you're not out of nappies yet. The best is yet to come.

At 67 I'm starting again, taking up serious eccentricity. :wee:

I dont care for the new fangled metric measurement system or the one those bunch of bloody Italians shoved on us for the last 1000 years.

Am hoping that Joe's next machine will be drawn in charcoal on parchment, measured in rods, roaches, perches and powered by a water wheel and an abacus.

Andy - old git ???? you're not out of nappies yet. The best is yet to come.

At 67 I'm starting again, taking up serious eccentricity. :wee:

Some people make me feel quite young. But many people who know me are of the opinion I took up serious eccentricity decades ago; why wait until you are old to have fun or conversely why stop having fun when you get there. The best part about being old is that nobody can dismiss you as a young twit.

Its not rocket science.



Andy

Dear Normsthename,

I now realise that I could be a genius. All I have to do is multiply by 25.4. Where have I being going wrong all those years??

Best wishes

Martin

Dear Normsthename,

I now realise that I could be a genius. All I have to do is multiply by 25.4. Where have I being going wrong all those years??

Best wishes

Martin

Perhaps you were dividing by 0.03937? :)

HaHa. Good one Geof.

Jason

Sad but true story:

We bought a machine for measuring cams. It was custom made by a very clever and intelligent albeit arrogant individual.

We kept getting linear readings that were just at tiny bit off. When we complained, he said it was impossible for that to happen and if it did, we out to write an SAE paper because it would be a stellar accomplishment.

We then PROVED using JOB blocks that the readings were off - low and behold, some new software magically appeared and the problem went away. One time we were talking to the programmer and he let it slip that they divided by 24.5 instead of 25.4 (the machine reads metric and we use inches).

We never wrote the SAE paper but we did trash 2 $3500 cam billets. The subject isn't discussed anymore but every so often the 24.5 factor gets tossed out just to remind the guy that he doesn't walk on water.

NASA has an 'oops' that crashed a space ship into a far away planet because of the feet versus meters issue.

In my shop we use inches. Why? My shop, my rules and we simply don't have metric problems. Having learned both, I can work in both but simply prefer imperial due to it being what I learned first.

The kids who have machine privileges to my shop were brought up on metrics are currently learning imperial units just fine, thanks. Hopefully, they'll thank me for it someday.

I realise that the usual conversion is to multibly by 25.4 and have always used this.

However I was making some printed circut boards and found that on large multipin chips that the legs slowly drifted out with the holes.

Many chips have a lead spacing of 0.1 of an inch. I was told by a printed circuit board manufacturer to use 25.39 and all would be OK, and it was. So the rounding usually used gives a slight error that is discernable over 1 1/2 to 2".

Sorry to confuse but in highly accurate situations be careful be very, very careful.

Cheers

I use both metric and imperial depending what the application and my mood is! I order timber in imperial so I generally end up doing the whole job in imperial just because Im in that frame of mind. Im in the EU.

When I was going to college, I recall the conversion factor as being 25.3936.

Supposedly the ANSI "standardized it" at 25.4 to make it easier. Yeah, why didn't they do that BEFORE there were calculators!?!??!!?.

Yes, when you REALLY need to be accurate, find the EXACT conversion factor. I bet the guys who imploded the NASA space capsule into a far away planet wish they did.

Perhaps you were dividing by 0.03937? :)

Dear Geof,

Speaking in my newly-found role as a complete genius, I rather tend to use

0.0393700787.

A brief suggestion to those with a larger number of digits on their calculators,

please spare us!

Best wishes,


Martin

I realise that the usual conversion is to multibly by 25.4 and have always used this.

However I was making some printed circut boards and found that on large multipin chips that the legs slowly drifted out with the holes.

Many chips have a lead spacing of 0.1 of an inch. I was told by a printed circuit board manufacturer to use 25.39 and all would be OK, and it was. So the rounding usually used gives a slight error that is discernable over 1 1/2 to 2".

Sorry to confuse but in highly accurate situations be careful be very, very careful.

Cheers


From Wikipedia:

In 1958 the United States and countries of the Commonwealth of Nations defined the length of the international yard to be 0.9144 metres. Consequently, the international inch is defined to be equal to 25.4 millimetres.

If the inch is defined as 25.4 millimetres I would have thought the correct conversion factor would be 1" = 25.4 mm

And yes the reciprocal of 25.4 is 0.03937007874 etc etc

I suppose for those people working in nano-inches this has relevance.

I suppose for those people working in nano-inches this has relevance.

Dear Geof,

All geniuses regard a nano-inch as plain sloppy.

Best wishes,

Martin

One Question:

so.....What size is a "Two - By - Four" in Europe anyway?

and: (The Existentialist in me can't resist)

If there's a "Two - By - Four", but nobody's there to measure it.....Is it really a "Two - By - Four"?


When the UK made the ( partial , distance still in miles !) conversion to metric years ago, I was renovating a house , I needed some "two by four" , The snotty little erk at the hardware store delighted in correcting my request, saying that it was metric now and was 50 x 100 . He them went on to quote a price per foot !

Dear All,

I have read the last few posts with growing alarm. For the last thirty years I may have laboured under a massive misapprehension, namely that one inch is exactly the same as 25.4 mm. I mean 25.4 with no extra digits. Is there anybody out here who can put my mind to rest?

I need help.

Best wishes

Martin

Dear All,

I have read the last few posts with growing alarm. For the last thirty years I may have laboured under a massive misapprehension, namely that one inch is exactly the same as 25.4 mm. I mean 25.4 with no extra digits. Is there anybody out here who can put my mind to rest?

I need help.

Best wishes

Martin

Like you need to do to see the Jolly Green Giant; look up, look way way up - well not way way just a little bit - I posted it from Wikipedia. The inch, 1" is defined, and has been since 1958, in terms of the metric system; 1 inch is 25.4 mm. Which is enormously convenient because it means you can cut metric threads using an imperial leadscrew on a lathe by having a 127 tooth gear in the gear train.

I posted it from Wikipedia. The inch, 1" is defined, and has been since 1958, in terms of the metric system; 1 inch is 25.4 mm. Which is enormously convenient

Dear Geof,

The owners of Wikipedia recently warned all students that the information might be a little less than accurate in some instances.

As regards convenience, 25.4 has one decimal place. I forget how many are required in the other direction.

Best wishes

Martin

1" = 25.4007mm

1" = 25.4007mm

No it doesn't; 1 inch is defined as 25.4 mm exactly.

edit
Machinery's Handbook, Twenty-Sixth Edition; page 2525, Table 1. Metric Conversion Factors
inch multiply by 2.54 to obtain centimeter (cm)

The 2.54 has a lowercase superscript a.
On page 2531 at the end of the table the footnote for a reads: "The figure is exact."

[QUOTE=Geof]No it doesn't; 1 inch is defined as 25.4 mm exactly.

"[/QUOTE

Dear Geof,

Thank-you for that. For a few minutes I genuinely had doubts about the conversion I have used for decades.

Best wishes

Martin

Sorry 1" = 25.407mm(heavy handed on the 0)

I guess we will have to disagree but a quick search of the internet and a look in my 'Colins' dictionary confirmed this figure(Although I quite regularly use 25.4mm myself, as I do not require to be more precise). I also believe cm are not a scientific measure unlike mm.

http://www.oldengine.org/members/diesel/Tables/comp1.htm

It reminds me of a story I heard about the French wanting to use the latest technology to re-weigh the original Kilo. The problem was how to clean the dust of it without scrapping off atoms from the Kilo thus effecting the re-weigh results.

I guess we will have to disagree but a quick search of the internet and a look in my 'Colins' dictionary confirmed this figure(Although I quite regularly use 25.4mm myself, as I do not require to be more precise). I also believe cm are not a scientific measure unlike mm.

In other words you disagree with Machinery's Handbook.

I am not sure where on the the net this 1 inch = 25.407mm but the closest my searches have come to this figure is 25.4000508001 and this is due to rounding errors.
So as far as I am concerned 1 inch = 25.4mm.

Jason

I also believe cm are not a scientific measure unlike mm.

[.

Dear bigz1,

The SI system may use metres, centimetres, or millimetres. I think, through the haze of memory, that it uses metres (I may be wrong).

What is absolutely certain is that one metre is the same as 100 centimetres and a thousand millimetres. Anybody who attempts to say otherwise is in need of a brief lesson in powers of ten.

Best wishes,

Martin

there was a change in the definition of an inch to correspond to 25.4mm. A quick google search didn't reveal when that change was made.

Well said Martin.

Searching further, under the SI system of units: 1 inch = 2.54cm= 25.4mm.
The above figures are exact.

Jason

never realized it was contentious, curious so i hit the search bar

ISO page:

http://standards.iso.org/ittf/PubliclyAvailableStandards/C030810E_FILES/MAIN_C030810E/text/annex_a.html

defines exactly 25.4

US & Commonwealth went to this standard '58 according to wiki

so if the dang parts don't find, it must be cuz its an old micrometer you're using :D

....The SI system may use metres, centimetres, or millimetres. I think, through the haze of memory, that it uses metres (I may be wrong)....Martin

The SI system now is mks ; metre, kilogram, second; for distance, mass and time with the Newton used for force.

Quite a while ago before metric became as widespread and places like the UK still based their measure on a king's thumb width :D the SI system was cgs for centimeter, gram, second and the unit of force was the dyne.

The US standardized linear measure on the metric system by an act of Congress in the late 19th century when the yard was defined by reference to the metre.

In 1958 the yard - metre relationship was made international and sometime around then; or at least between the 19th century act and 1958 there was some question as to whether the US standard yard was the correct length. It might have been out by 0.0001" or something.

The 1" = 2.54 cm exactly has been in effect since 1958.

And it all is referenced back to kazillions of wavelengths of the light emitted by a cesium atom going through a particular energy transition which I am too lazy to research in detail.

And before that it was referenced to the distance between the pole and the equator on a line passing through Paris or some other place in France. The metre was intended to be one ten millionth of this distance. Unfortunately they got it wrong so for many years the standard for the metre was a platinum bar with a couple of scratches in it.

But then again maybe I have it all wrong.

edit:
Sorry my chauvinism is showing. The 1958 standardization was not truly international it only included the US and the Commonwealth of Nations (which was pretty darn close to international back then).

Searching further, under the SI system of units: 1 inch = 2.54cm= 25.4mm.
The above figures are exact.

Jason

Dear Jason,

Thank-you.

Best wishes,

Martin

But then again maybe I have it all wrong.

Dear Geof,

As long as one inch equals 25.4 millimetres, I really do not care!

Thanks

Best wishes,

Martin

Grabbed my digital calipers and dialed in 1.000 in. Then I pressed the mm/in selection button and, voilà, out popped 25.40mm. Re-pressed the mm/in selection button and, lo and behold, back to 1.000 in. Pressed the mm/in converter button and, what do you know, still 25.40 mm. Snuck up on the conversion button and...


It works :) , give it a try ;) ,

HayTay

I though the whole idea behind the metric system was that we are too stupid to deal with fractions. As if it was too hard to get the brain around. Though last time I checked .4 of a mm is a fraction, I have yet to hear anyone use the correct whole unit term for portions of a millimeter. Micrometer, Nanometer ect. I hear people say a tenth of a millimeter and so on. When I check my calipers I get 25.4 for the inch, I have no problem with this, but is not 4/10ths a fraction? I actually do not care, I just get a little steamed over the idea of one system being better. I guess what ever it takes to feel good about yourself in the morning, if using the metric system does it for you, than great. :cheers:

Just some thoughts at o'dark thirty after tool long at cad
:cheers:

im still trying to figure out how to punch in fractions in mastercam

I though the whole idea behind the metric system was that we are too stupid to deal with fractions. As if it was too hard to get the brain around. Though last time I checked .4 of a mm is a fraction, I have yet to hear anyone use the correct whole unit term for portions of a millimeter. Micrometer, Nanometer ect. I hear people say a tenth of a millimeter and so on. When I check my calipers I get 25.4 for the inch, I have no problem with this, but is not 4/10ths a fraction? I actually do not care, I just get a little steamed over the idea of one system being better. I guess what ever it takes to feel good about yourself in the morning, if using the metric system does it for you, than great. :cheers:

Just some thoughts at o'dark thirty after tool long at cad
:cheers:


I think the elimination of fractions is between the different measurements of the metric system ie 1m = 100cm = 1000mm and not between the imperial and metric system, everything relates in powers on ten. If we had 367mm, then that is equal to 36.7cm which is equal to 0.367m.

Fractions can never be eliminated simply because its number, 1/2" is represented as 0.5" in decimal form, 1/3" is represented as 0.3333 with the 3 repeating.

Its not that one system may be better but everyone needed to come to a standard format and the metric system was defined.
Use the system that you are comfortable with, I use both and never had problems. :D

Jason

This debate on metrics clearly goes back a ways:

http://lamar.colostate.edu/~hillger/dates.htm

Even the "official" conversion changed and the "correct" one could be "incorrect" depending on the time frame the conversion was done.

Moroever, the conversion from inches to mm and vice versa is NOT universally accepted at 25.4 or the inverse there of. Witness the following:

www.nist.gov/metric

www.simetric.co.uk/

If you delve deeper into the "metric conversion standards" search on Google, you will surely find different factors depending on where you go and which conversion they used at the time.

The difference between 25.4 and 25.39 is relatively of little consequence in one or two inches. However, as one member pointed on on PCB layouts, the addition of the "error" as you get to longer and longer conversion lengths becomes substantial.

Remedy (there is no solution) that works for us is to ask your client what factor they use when converting metric to imperial and vice versa. If it is 39.36 or 39.37 or 25.4 or 25.39, it is at least consistant with what THEY are expecting.

Then go off on your merry way and make it using the appropriate MIL standards that we all need to follow with your metric or imperial scales:

MIL- TFP 4.1 (Make It Like The Frigging Print For Once).

After looking at more sites on conversion I am see that persons doing conversion are rounding off quite a few decimal places. Some sites have 1mm = 0.03937 inches which causes a problem when reconverting to mm.

If 25.4mm is defined as 1 inch

then this would imply that 1 mm = 1/25.4 inches,
so we get 1mm = 0.03937007874015748031496062992126 inches.

If we take the reciprocal of 0.03937007874015748031496062992126 we get 25.4 .

If you do not round off you will not get an error.

Since I am using the microsoft calculator on my computer I am limited by the number of decimal places that it can display.



Jason

After looking at more sites on conversion I am see that persons doing conversion are rounding off quite a few decimal places. Some sites have 1mm = 0.03937 inches which causes a problem when reconverting to mm.

If 25.4mm is defined as 1 inch

then this would imply that 1 mm = 1/25.4 inches,
so we get 1mm = 0.03937007874015748031496062992126 inches.

If we take the reciprocal of 0.03937007874015748031496062992126 we get 25.4 .

If you do not round off you will not get an error.

Jason

Jason, stop it you are being too logical and rational, tha's no fun, surely it is much more fun to needle the stick-in-the-muds who find a need to attack metric or manufacture a controversy. I live in Canada which started out to convert officially to metric but stalled partway. There was a sector of the population who predated the introduction of metric by many years and represented a large voting block and one government a few years ago repealed the legislation for the final step as a vote buying gimmick. (I suppose I should put the 'In My Humble Opinion' after that.) A lot of the posts in this thread a somewhat reminiscent of the types of arguments put up against metric back then.

When you are familiar with it Metric is easier to use it alone than inches and decimal units based on the 1/2, 1/4 etc series of fractions but it is an absolute pain switching between the two systems sometimes when you also have to take into account tolerances; quick; what is 0.875" =/-0.002" in metric? This is where the opposition stems from I think.

It is amusing how vehement people get in resisting something they are unfamiliar with or which they perceive is being imposed on them from outside. I have met a few software people who are perfectly happy doing mental conversions between binary and base ten and back and forth between these and hex and bcd but who almost foamed at the mouth at having to convert from inches to mm.

After looking at more sites on conversion I am see that persons doing conversion are rounding off quite a few decimal places. Some sites have 1mm = 0.03937 inches which causes a problem when reconverting to mm.

If 25.4mm is defined as 1 inch

then this would imply that 1 mm = 1/25.4 inches,
so we get 1mm = 0.03937007874015748031496062992126 inches.

If we take the reciprocal of 0.03937007874015748031496062992126 we get 25.4 .

If you do not round off you will not get an error.

Since I am using the microsoft calculator on my computer I am limited by the number of decimal places that it can display.



Jason


This is all true if you hold an infinite number of decimal places during your calculations. In reality the mantissa of most calculators is only 8, after which roundoff errors do occure. I had an example I used to teach my students, and I can't remember it off the top of my head. (If I get really ambitious I'll look it up. But I doubt I'll get that ambitious.)

But it was something like doing the same calculation series and in one case rounding to 1 decimal place each set of the series while in the second case rounding to three during the course of the series of calculations. One answer turned out to be almost double the other. So roundoff can make a difference.

But, for 99% of what were doing here, you are right.

....So roundoff can make a difference...

Round off error is one reason why weather forecasting is so difficult and is really what led to the discovery (invention?) of Chaos Theory.

But in practical terms the error in using 0.03937 and getting 25.40005080 etc etc is irrelevant; the error is just over 50 nanometers.

Round off error is one reason why weather forecasting is so difficult and is really what led to the discovery (invention?) of Chaos Theory.

But in practical terms the error in using 0.03937 and getting 25.40005080 etc etc is irrelevant; the error is just over 50 nanometers.


Interesting, now I had always been led to believe that chaos theory and non-linear dynamics came out of Celestial Mechanics and the works of Aleksandr Lyapunov (Lyapunov stabilities) and H. Poincarie (planetary dynamics). Of course, if my parents had known of the existence of chaos theory when I was young they would have said the origin or all chaos and disorder was my bedroom.

And yes, on a practical level you are totally correct.

Wow. Little did I know what a storm my comment would make. After reading your comments and doing some further research I concede the point and agree 1" = 25.4mm. For the final word and queries on all SI units I suggest you check out this link from the horses mouth.

http://www.bipm.fr/en/home/

I will be burning my 'Collins dictionary' (flame2) and buying the Oxford edition. Many thanks guys. :cheers:

Liam

The difference between 25.4 and 25.39 is relatively of little consequence in one or two inches. However, as one member pointed on on PCB layouts, the addition of the "error" as you get to longer and longer conversion lengths becomes substantial.

jesus! what kind of tolerences are they holding on a PCB board?

At 5Feet the difference of 25.4mm x (5feet x 12in)=1524mm or 25.39mm x (5feet x 12in)=1523.4mm. So at 5ft the difference is .015" at 5ft!

Interesting, now I had always been led to believe that chaos theory and non-linear dynamics came out of Celestial Mechanics and the works of Aleksandr Lyapunov (Lyapunov stabilities) and H. Poincarie (planetary dynamics). Of course, if my parents had known of the existence of chaos theory when I was young they would have said the origin or all chaos and disorder was my bedroom.

And yes, on a practical level you are totally correct.

From wikipedia (if you are willing to trust it :D )

An early pioneer of the theory was Edward Lorenz whose interest in chaos came about accidentally through his work on weather prediction in 1961. Lorenz was using a basic computer, a Royal McBee LGP-30, to run his weather simulation. He wanted to see a sequence of data again and to save time he started the simulation in the middle of its course. He was able to do this by entering a printout of the data corresponding to conditions in the middle of his simulation which he had calculated last time.

To his surprise the weather that the machine began to predict was completely different from the weather calculated before. Lorenz tracked this down to the computer printout. The printout rounded variables off to a 3-digit number, but the computer worked with 6-digit numbers. This difference is tiny and the consensus at the time would have been that it should have had practically no effect. However Lorenz had discovered that small changes in initial conditions produced large changes in the long-term outcome.

Although others discovered it independently around the same time.

Back in the early 1970's I had an example of how round-off error can scupper your plans. I worked as an instrument tech for a company that was developing a diving computer that would automatically calculate and display time left, decompression time, etc. They could not get it to work and 'killed' numerous theoretical divers in simulations. Finally they found the reason was round-off error in the numerous calculations involved. For me it was a summer job and I lost contact with them when I went back to university so I don't know if they ever stopped 'killing' divers.

Wow. Little did I know what a storm my comment would make. ....Liam

Look on the New Posts page. There is a column titled views and for most threads the number there is much greater than the number of posts. When I get involved in a 'storm' as you describe it I am thinking of all the viewers that may benefit and learn something new or get some incorrect ideas corrected.

Since I am using the microsoft calculator on my computer I am limited by the number of decimal places that it can display.



Jason

Dear Jason,

You are also putting your trust in Bill Gates, his empire, and his software people. Unwise.

Best wishes,

Martin

Geof,

I checked on my sources. The American Physical Society says (and here was the first point my memory failed me on) H. Poincarie would have been forced to develop chaos theory in the late 1880's if he had lived another 10 years and had continued on the same line of research he had persued most of his life (the caluclation of planetary orbits which all show a bit chaotic behavior when you factor in all the gravitational interactions of the other planets in a 3 or more body system).

(second point of early senility) Aleksandr Lyapunov solved the equations for Lyapunov stabilities. But at the time there was no real application for them. Today the Lyapunov exponent is one of (if not the) the most fundamental measurement of chaos. So he had the solution to a question that wouldn't be asked for another 60 years.

It's like Kazula-Klein theory The theory that physics operated in more than 4 dimensions... current wisdom is 21 dimensions if I remember right. i.e. hyperdimensional physics to use Jack Sarffati's terminology). Developed in the 1920's and enjoyed a brief flurry of interest for a few years and then lay dorment until Whitten figured out that it was the only workable solution to superstring theory.

If you want to see a real mindblower you should check out Brian Greene "The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory" (the DVD, not the book)

DUH.

I think some of the postings that have arrisen on this thread create new corrolaries to chaos as this thread has gone beyond theory and become completely, not randomly chaotic.

Long live the chaos, and from the looks of this thread, it is alive and well and approaching immortality...

Now, what does 24.4 or its inverse factor(s) have to do with the perverse nature of inanimate objects???

DUH.

I think some of the postings that have arrisen on this thread create new corrolaries to chaos as this thread has gone beyond theory and become completely, not randomly chaotic.

Long live the chaos, and from the looks of this thread, it is alive and well and approaching immortality...

Now, what does 24.4 or its inverse factor(s) have to do with the perverse nature of inanimate objects???

Probably not much although seeing as how we have drifted into chaos theory perhaps it is a strange attractor :rolleyes: but we can drift further :D .

Chaos theory also gets involved with animate objects. The metabolic control of heart rate shows signs of being a chaotic system. A normal beating heart is a feedback system that oscillates slightly around a 'set point' and this oscillation has a characteristic period. Some studies have suggested that the period of this oscillation, or more precisely changes in the period, can be used to predict a heart attack. A doubling of the period is okay but if it doubles indicate again this can presage catastrophic instability where the system does not return from one of its oscillatory swings and justs wanders of into fibrillation.

Geof: now that post got my head to start throbbing.....

Geof,.....If you want to see a real mindblower you should check out Brian Greene "The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory" (the DVD, not the book)

I have recently become a fan of Mordehai Milgrom. Probably because a recent New Scientist article characterizes him as 'Gravity's Gadfly'.

Can someone post a copy of the plans in Cubits and Furlongs? Us old farts have a tough time with this inchies and feetsies thing.

JK.. got my jgro completed finally. :)

"I live in Canada which started out to convert officially to metric but stalled partway. There was a sector of the population who predated the introduction of metric by many years and represented a large voting block and one government a few years ago repealed the legislation for the final step as a vote buying gimmick."

They rolled the dice and lost: 1) They assumed the future of the country lay in more trade with Europe, which is metric obviously, and not the US (though the US was saying they would go metric), with which we had the largest trade dependency in the G8 by a factor 2 in the period in question. 2) All they repealed was the laws that made using imperial in business illegal, etc... Which is kinda embarrassingly like Bill 101.

I think the metric system just has a better name, like an indie rock band. I undertake with little success to make it subservient by referring to it as "Client State Measurements". After all if we are the imperial empire then in polysci terms France the originator is a "client state", along with others like Canada that use this system. Not working out to well for me, people seem resistant, but I try.

Has the US got rid of the department of metrification yet? I heard for a while they had given up on the endeavor but kept the bureaucrats.

I use both, but you can't simply multiply by 25.4 to convert from inches to mm when using the formula I use for aspherics- it just dun work, so I chuck it back at the designer and get him to spend a week doing it (optical designers are the bane of my life).

Here's the formula (for a laugh):

Z=[X^2/{R+SQRT(R^2-((K+1)*X^2))}]+A1*|X| +A2*X^2... A12*X^12

And they sometimes use c instead of K, where c= 1+K or 1-e^2, and they sometimes get all the signs wrong. I hate optical designers...

Incidently, did you know that Carrat (the size, ie weight of a diamond) was an ancient civilizations word for a grain of wheat (or some cereal).. it was the weight of one grain.. which also gives us the weight of small amounts of medicine.. a grain was exactly that.. a grain of wheat or barley.. can't rememeber.. going senile lol

the metric system is the salution for the non existant problem......unless fractions are just too tough for you or you are french, in which case they must be. ;-)

If you really want to convert these to almost any other units (including furlongs and cubits or even parsecs)
www.onlineconversion.com

We have some products in inch and others in metric. It depends what units the customer wants. The real fun starts when we design and build the prorotype in the US, then have the production done in South Korea.
Engineers in the US create the models, then all of our prints are now "dual dimensioned" Inch [mm] by our outsourced drafting department in India, ideally the very night after we create the models - Or so went the sales pitch! Seriously!

One of my favorite things about Solidworks is that if you are working in metric, simply type " after a number and it will convert for you. If you are working in in, simply put mm after the number and it converts it for you.

NEATman

That sounds like a great leap forwar, when I convert a plan in my CAD, it resizes the whole shebang in the other system, so the 20 inch guitar becomes 20 cm. Of course it can be adjusted in size easily enough...

Pop Quiz Just for fun.(nuts)

So, I am making a very accurate bearing seat. I use metric dimensions, however the drawing has been made in inches.

I am willing to work in inches however neither my cam system nor my american haas controller can have fractions entered into it.

So I have to use a decimal inch (what imperial people resort to when they realise that inches are so difficult to deal with).

The dimension is 13/64 (and thats a real dimension). So what pray tell do I enter into my cnc machine?

Now can it be seen that for some applications inches are awkward.

Dom

you'll have to enter ".203125", or if you want to break it down simply, divide "1" by "64" to get 1/64" (.015625), then times it by "13" to get 13/64" (.203125), inches are not easy in comparison to mm, I learnt inches first, but was taught 3D Modelling software based around a millimeter system, so i had to learn it, didn't regret it, millimeters are a lot easier but in order to change over i'll have to learn quite a few "standards" which will take time that i don't have and disrupt my whole way of working, it's just not the right time for me now.

13/64" = 0.203125"

How to derive? Divide 13 by 64.

DUH

Dang, each day you learn something new :withstupi .

Just thought I would point out something... I don't know if it’s been said or not... but let’s go deeper than just machining and look at engineering and science. How volume transfers to 3D and how when you know how many cubic centimeters a box has you automatically know how many liters will fill the box and so on.

Science may be the illegitimate step child of math... but you still gotta support the lil booger.

OK that was an easy one for starters.

Question 2: The next dimension on the drawing is a tiny clearance. The dimension is 1/72nd of an inch. What do I enter into the computers???


Answers please.

Good Luck
(chair)

13/64" = 0.203125"

How to derive? Divide 13 by 64.

DUH

1/72" --> Divide 1 x 72 = ???

Give a man a fish, he eats for a day, teach a man to fish, well...............:)

I god had meant us to us the metric system, we would have been born with ten fingers :)

...ten fingers and two hands...that's three sets of four (and definetly not four sets of three)...the right four fingers, the left four fingers and the combination of the two thumbs and the two hands. Twelve has 1,2,3 as prime factors and ten has 1,2,5 ...so isn't it obvious.......we should be working in the 'unified sexigesimal system' Any elegant system of measurement will be based on a proportional and not an absolute reference. That meter stick sitting somewhere in France is about the funniest thing I can think of.:violin:

Chris

Surely you jest and can't be serious?!?!?!?!?

Let me try this again:

1/72 = 1 divided by 72 = divide 1 x 72 where x equates to the "by" in 2x4 or, ultimately 1/72"= .013888888888888"

EDIT To address the inevitable next question for the metrically confined/limited members, multiply the quotient of 1/72 by 25.4 and you'll get mm or 0.01388888888" = 0.352777777mm or 352.7777777 microns END EDIT

If you don't know how to fish by now, perhaps you really do need to starve.....

Are we talking metric or standard entry... if it was metric... follow the usual formula ... or such... if it is standard in a drawing.... why are you even using fractions. Any machinist will tell you that using fractions on a drawing is not a good idea for a number of reasons.

One of which being a fraction is a perfect number and could NEVER I be achieved in full. Their will always be some infinitely small number that will exist to break that measurement.
The other being... the last time I checked a FANUC did not work on a fraction system going from 1/10000 to 9999/10000.......why would you draw in a format other than what you plan on using.
The third being that when machining all sorts of factors would eliminate the need for 0.013888888888888888888888888888889
A chip could kill off a dimension to begin with... on top of that I am sure that tool pressure could even eliminate that.

I don't know what I am talking about..... But these are the thoughts I get....... and I don't understand why it would matter if you just programmed using the same structure for both. A number is a number and when machining most machinists won't even try to achieve a tolerance tight enough to not hit by rounding up half a thousandth... the part requires grinding or such... or at least this is what I have seen.

I'm interested in seeing the rest of the answers.... I may learn something valuable..... You guys really have me thinking.

Well theres plenty of sarcasm floating around now.

I think you mean
1/72 = 0.01388888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
8888888888888888888888888888888888888888888888888
888888888888.......

Where would you like me to stop.

So if I buy a 1/72nd inch tap or reamer or any tap that is a multiple of 72, what size is it

Is it

0.01389
or

0.013888889
or

0.0138888888888889
or

0.01388888888888888888889

I dont know, and it depends on what machine shop decides to use for decimal places.

So what clearance do I give it? I don't know because we cannot actually get a finite number for its size.

Anybody ever seen that pi calculator that calaulates pi to several billion digits and it just keeps going and going.

Discuss

Dom

I. A number is a number and when machining most machinists won't even try to achieve a tolerance tight enough to not hit by rounding up half a thousandth... the part requires grinding or such... or at least this is what I have seen.

.
to say that is rediculous
a good machinist always aims to make the dimensions of the parts dead nuts ,many parts that i have done had dimensions within a thou ,and on a good machine it is no problem to achieve those dimensions unless it s a pretty funky part
5 decimal points is best for tapping ,otherwise added pressure is on the tap due to the fact the teeth arent following the other ones perfectly ,especially so on deep holes
throw in two decimal points the next time your tapping and see what you get

Surely you jest and can't be serious?!?!?!?!?

Let me try this again:

1/72 = 1 divided by 72 = divide 1 x 72 where x equates to the "by" in 2x4 or, ultimately 1/72"= .013888888888888"

EDIT To address the inevitable next question for the metrically confined/limited members, multiply the quotient of 1/72 by 25.4 and you'll get mm or 0.01388888888" = 0.352777777mm or 352.7777777 microns END EDIT

If you don't know how to fish by now, perhaps you really do need to starve.....


I really think he is pulling your leg.:D :D

Jason

to say that is rediculous
a good machinist always aims to make the dimensions of the parts dead nuts

Dead nuts to what?
The number that you decide to round the error to or the number that the customer rounds to or the number that another subcontractor rounds to........


Next question.

On a thread of 1/72 inch pitch. How deep a rigid tap (assuming the rigid tap is perfect for arguments sake)..can a 1/72" pitch tap be threaded, rounding the decimal measurement of 1/72" to 4 decimal points, before it breaks due to the error making it misalign.

Who will take the challenge to work it out.

Have inches of fun.

Dead nuts to what?
The number that you decide to round the error to or the number that the customer rounds to or the number that another subcontractor rounds to........


Next question.

On a thread of 1/72 inch pitch. How deep a rigid tap (assuming the rigid tap is perfect for arguments sake)..can a 1/72" pitch tap be threaded, rounding the decimal measurement of 1/72" to 4 decimal points, before it breaks due to the error making it misalign.

Who will take the challenge to work it out.


Have inches of fun.

how can anything get more simple , i dont decide the numbers , the customer decides the target dimension and gives a +- tolerance , dead nuts is the target dimension
a FOOL would try to work within the tolerance rather than aiming for the target number because you are minumizing your room for error ,which is what the tolerance is for to begin with

as for a 1/72 pitch tap ,i"ll let you figure that one out for yourself

Woops... I didn't mean the Dertsap.... I meant rounding up the tenth of a thousandth based on the answer going out infinitely... I left out the HUNDREDTH OF before the thousandth. I was going back into the rounding bit. HAHA boy that sure made me look dumb..., need to look at how I word it before I send it(nuts) to myself.

IE

.013888 being rounded up to .01389
would be rounding up causing an increase of 2 hundredths of a thousandth
.013885 being rounded up to .01389
would be the equivalant of rounding up 5 hundredths of a thousandth which is equal to half of a tenth

That make any sense?? Or am I still missing something? I was trying to say that is it near impossible to fight over the hundredths of a thou. when a machine is capable of mass production for the most part in the tenths. Would you agree with that? Aircraft parts go to a tenth according to a programmer I just got off the phone with.

Having never programmed in metric...I am curious as to whether or not someone programming a machine in metric would be able to create a readable machine movement smaller than a tenth of a thou. I thought I read this somewhere.

Also... what are you running that will allow you to program to the hundredths of a thousandth. I am used to the FANUC 0M and it just stops at .0001 and at that movements made by the machine can only be regulated by hand control to the tenths. You may be programming in hundredths of a thou. but I seriously doubt you are acheiving them. Tool pressure alone on the most stable of tools would begin to set in at that point. Its just like when drawing in CAD..... I might tell that line to start at x0y0 and end at x0 y2.345678645809328508583250983509809583958905893850975892380840
499959584 ...but that isn't going to happen, the software has its limitations.

Nothing is perfect... and never will be. Besides a fraction is an imaginary number... it is not even a number it is an imaginary placement of a number between a number at a set point based on the use of two integers as a numerator and denominator. Just as a thought. So... I really think the answer for the whole form is there isn't a right or a wrong.

But I think I'm going to side with the metric guys. The system is much more useful in the broad scheme of things and standard is as dumb as can be. It is a sign of the need for a change of times. I mean cmon links furlongs..... heck most of you cant even tell how big one of those are and how many inches are in each... I sure can't. But ask someone how many centimeters are in a decimeter and they could pull it off the top of thier head if they use the system daily. More power to you my metric loving friends and congratulations on finding one the reasons the US has to fight to continue as a superpower.

i hear ya man:D

I just wonder if manufacturers in China give a rat's a## about the measurement system on the drawings or files they are sent.

They must get sent tens of thousands every day, and I very much doubt that they care a great deal whether they are in imperial or metric units. They get on and manufacture. Meanwhile back west, we indulge ourselves with debates such as this.

Isn't it time to get real and admit that both systems work??

Just a thought

Martin

Right on Martin.... but who is to judge what works. Again I go to the bigger picture........ Sure it works for the CNC programmer...and in other things...but why complicate the whole picture. Engineers find it easier to calculate scientific data in metric... machinists (here in America for the most) find it necessary to program in standard. Mostly because it is what we are used to. Amazingly the so called grease monkeys of society (mechanics) have found a way to adapt. So I am sure we too could find a way. No offense to mechanics anyway... I am just making fun of the ignorance of society.

So which is more efficient... a process that can be used efficiently from start to finish ... From engineering to final product. Or something that creates train wrecks and complication.

It all comes to commonsense versus tradition. For goodness sakes........We measure vehicle motors in Cubic Inches and then describe it in liters..... Ever notice that bike motors don't have the need to say 150cc and then liters.... it can be determined by using the tens process.

We have to face it... we are in a global economy ... with global trade... we have to learn to evolve as a country and quit trying to be the last piece of the puzzle to fit. From a philosophical view I see it just like global warming.... we know we messed up... and have to find some sort of way to feel in control.

Hey x6,
I've been in the engineering business since '82 and I remember vividly the US goverment proposal to switch to metric. It made since then and it still makes sense. I've had jobs where I worked on Italian and British designs. I can say it was very easy to understand the tolerances of the metric system. I think its called the DIN system of tolerances.

Then, all of a sudden the government's effort to switch to metric system desolved. Pooff it was gone.

I don't think anyone mentioned the Mass system differences between metric vs imperial. When doing calculations for acceleration us imperialist must cipher the differences of pounds mass vs pounds force. Or use Slugs in our calculations of speed and acceleration. I like them both, but I'd rather have metric.
Dave

Would you please explain pounds/mass and pounds/force. Also, having the opportunity to experience metric at its most full, would you say that momentum and inertia are easier to equate in metric than in standard? I am curious of the metric system's traits.

I also am curious as to whether or not a machine can make a registered movement of less than the equivalent of one ten thousandth of an inch when using metric alignment

I believe the last question if true may be the answer to the alignment of the 1/72" pitch tap listed above? I would like to know the answer to that by the way. Help us young'ins help ourselves!

Hey x6,
I've been in the engineering business since '82 and I remember vividly the US goverment proposal to switch to metric. It made since then and it still makes sense. I've had jobs where I worked on Italian and British designs. I can say it was very easy to understand the tolerances of the metric system. I think its called the DIN system of tolerances.

Then, all of a sudden the government's effort to switch to metric system desolved. Pooff it was gone.

I don't think anyone mentioned the Mass system differences between metric vs imperial. When doing calculations for acceleration us imperialist must cipher the differences of pounds mass vs pounds force. Or use Slugs in our calculations of speed and acceleration. I like them both, but I'd rather have metric.
Dave


When the big push to convert back then I worked in a lab next to a prototype machine shop with about 20 toolmakers old timers who could fabricate anything (no cnc) some of them legends . When the first Metric drawings came down from the engineers the place tunred into Kaos, you should have seen these guys converting every dimension in the drawing just to start cutting it sounded so rediculous then , it only lasted about 5 months .These guys knew what cutting 5 thousands on the lathe looked like, but had no idea what cutting .5mm looks like

RE: the metrification of America

Prior to this idea, we had any number of machine tool makers who literally made their machine tools in the good old USA. Some of the legends included Bridgeport, South Bend and goodness knows how many more.

They essentially had a captive market as they pretty much were the only suppliers of Imperial unit machine tools. Then some creative folks learned that by changing the dials on their metric lathes, mills and VMC's, they could take an otherwise metric lathe/mill/VMC/whatever and compete in the US machine tool market. If you know what the metric equivalent is to an Imperial unit (distance wise), it don't matter what you cut as long as it cuts what the customer is expecting.

So, the decimation of the US machine tool industry started. Low cost machines, created by state sponsored industries, summarily started their attack on the US machine tool industry. The industrialists like this because it enabled them to get cheaper machines via importing. THis also proved to be a boon to the US hobbyist as used machines became much more affordable or new clones came in at a fraction of the price that the one that had been knocked off.

This, one would say, was good for the economy as it made it much more convenient to buy, lease or otherwise afford machine tools that would have been unaffordable otherwise. However, the spin-off is/was that the industry got decimated. We now rely on off shore sources to provide our machine tools as well as any service parts for them (if you can even get service parts).