lets say im a venture capitalist and the money is in gauge blocks.

i can see making a B grade gauge block set from an A grade but if you want to make AAA you cant ake it off another AAA block set and there are no set grades higher than that.

is there a master gauge block in ISO headquarters that is exactly 1" whereby every other measurement on earth is based? How does cumulative error in measurement not form over history when you are working over one single gauge set?

jo blocks is where the money is these days??

your Q is interesting.....but interesting enough to compel me to plough through 145 pages .......bet your answer lies within

http://emtoolbox.nist.gov/Publications/NISTMonograph180.pdf

aren't distance standards reference to so many wavelengths of a kind of light, measured in Angstroms oir some such thing?

lets say im a venture capitalist and the money is in gauge blocks.

i can see making a B grade gauge block set from an A grade but if you want to make AAA you cant ake it off another AAA block set and there are no set grades higher than that.

is there a master gauge block in ISO headquarters that is exactly 1" whereby every other measurement on earth is based? How does cumulative error in measurement not form over history when you are working over one single gauge set?


It works for various gage blocks. Say your .099" gage block is a B or shop grade. It can be ground down to a .098" gage block. Given that you can grind or lap to lab standards. Even if you can grind that good, you still need to be able to measure that good.

The standard for all measurements is actually time. Measuring the time is takes for a Iodine stablized HeNe laser to reach one side to another.
Master gage blocks are taken from manufacturers and sent to NIST, and other national labatories. Then round robin tests are conducted.

There is no "exact" 1" gage block. Even "Master" gage blocks have tolerances.

Hi, what about your environmental temperature?
I worked in the gauge room as a gauge inspector at the last job I had and the place was maintained at 68 deg C all year long. Bloody freezing. Couldn't stop going for a leak every five minutes. Didn't do much good for my nose either, always runny, and if you think cold hands are signs of a warm heart, forget it.
When the summer weather was 35 deg C outside and it was 68 deg C inside, you can imagine how many times I had a bl###dy cold and flue from just going in and out to the toilet. Never again.
One thing always puzzled me, All the gauges and micrometers were set by us at 68 deg C, and then issued out to the factory to be used at ambient temperature, usually 35 deg C in summer.
This is either blindly going where common sense dictates otherwise, or just an industry rigid procedure that ignores the real world.
Ian.

...One thing always puzzled me, All the gauges and micrometers were set by us at 68 deg C, and then issued out to the factory to be used at ambient temperature, usually 35 deg C in summer.
This is either blindly going where common sense dictates otherwise, or just an industry rigid procedure that ignores the real world.
Ian.

If the parts are also at 35 deg C when measured this is valid within the difference in thermal expansion between the part material and the measuring instrument material and this difference is probably much less than the intrinsic error in the gauging.

Incidentally I do hope you mean the room was held at 68 F. otherwise you must have much tougher hands than me.

Most quality labs are where the standards are kept are 20 deg C. Usually plus or minus 1 C. Humidity is also controlled in some labs to a relative humidity of 30 percent. I may be off on this number a little.
It's true most manufacturing envionments are not kept to this temp or humidity. However, if you take a part and move it to the quality lab and let it meld to that envionment, you can usually inspect it and make necessary changes out on the shop floor.
In Calif., the summer temps can easily hit 40 deg C or higher. Being in a quality lab with a controlled temp of 20 deg. C has it's effects as well.
Back to the orignal post. Ceramic gage blocks are where it's at. Dimensionally stable. 10 times the wear resistance of steel.

Hi Geof, oops, got a bit mixed up with F & C degrees. Yes it's 68Deg F.
I suppose the expansion rates would be the same across the spectrum for gauges and jobs. Never really thought about it.
Hi tooluser, never used ceramic blocks, but I expect the fact that they don't rust from hand sweat is a bonus, also much lighter for a boxed set of 110 pieces.
I was at an auction in Melbourne, a couple of years back, and the General Motors Holden plant was closing down with everything going up for grabs.
The auction went over a week or two, and I went to the toolroom part.
It was enough to make you weep when the tooling was bundled together and sold off in job lots.
Sets of micrometers going for a few dollars. I got a gauge block set for A$20, and ended up bidding against a chap who had a farm and thought the blocks were variable packers for the mill.
All the dealers were there, and anything the dealers were bidding on you can bet your boots it was worth something, so we always watched those items and outbid the dealers who were going to resell them at profit.
I don't know how the gauge blocks are going to react to my "laborotory" (garage) temperature range which varies from 50 degrees C in summer down to 2 degrees C in winter.
No matter what state a set of gauge blocks are in, and I mean a light coating of surface rust at the extreme, they are still a very usefull item to have in the tool collection. As long as they'll wring together they will work.
I wonder how many people use the protective cover slips when they use them?
Now we're really getting technical. Next thing you'll need is a decent surface plate.
I've been looking around for years for a plate about 2 ft square but nothing has appeared yet.
One of the guys at the model club I use to go to had a small foundry and he was selling iron castings for 12" plates, fully ribbed ready to machine and scrape etc. At a A$100 a plate, and you need three to get one, it was a bit out of reach.
Ian.

...As long as they'll wring together they will work...

I think this is the first time in many years I have seen the correct spelling for 'wring together'! Give the man a gold star:) . And on an equally serious note I realise that flakker's orignal query is unanswerable. In Australia the standards would likely be at CSIRO Headquarters but this institution cannot possibly exist in flakker's country.

Republic of OZ? well I never, after all these years.

Hi all, does anybody know what a "precision table" is used for?
I bought this item at a tool auction, as part of some gear.
It is about 125mm (5") in diam, and 75mm (3") thick, fine finished top surface and is in a wooden case.
I would hazard a guess that it is the equivalent of a set of parallels for use on a surface plate to bring the part, to be measured, up off of the deck to allow easier acess.
It could be used by itself like a mini surface plate but it's too small to get any measuring tools on, such as as height gauge.
I was just thinking it might be used as as hand held reference surface plate to check the surface flateness of a machine part, but it's too small for any significant area indication.
Ian.