Hi guys,

I want to build a cnc machine, similar to the cheapCNC machine, except I will use the Xylotex Controller to speed up the travel. I would like to use 150 oz motors or so... any suggestions? What do I use for a power supply?

I will probably stay pretty close to the size of the cheapCNC. What do you guys recommend for material. I don't really want to use MDF. I don't want to use aluminum either because I have no experience machining it. I notice that Steve Thompson is now using some kind of plastic. Is that a good choice? What is it called and where do I get this plastic?

I figure I can build this machine for under $1000. What do you think?

Motors?
Power supply?
Plastic material?

Thanks,

Mike...

get the 116 oz steppers from Xylotex

Look on ebay for a powersupply. Get a 24 volt one.

What's wrong with MDF? I have no idea where to get that plastic.

Build first, buy motors and controller later.

Just my 2 cents.

Eric

Hi,

Bob Campbell uses a plastic called UHMW to build router clamps, maybe it would be good for the rest of the machine as well. I never would have thought you could build a functional machine out of MDF, but many of the people on this site have made some impressive machines with the stuff, so I wouldn't dismiss the possibility of using it particularly if you are on a budget. Plastic can cost more than aluminum in some cases (I don't know about UHMW)

Steve

Okay, you guys have convinced me to take another look at MDF.

Let me ask you about anti-backlash nuts. I can buy them for $19 each... But can I make my own by buying a flanged nut, and adding something to make it anti-backlash.

I'm thinking about using drill blanks for the rails, with linear recirculating bearings. On the machine that Abasir built in a weekend, did he just capture the rails in a bore in the sidewalls, or did he attach them somehow?

Mike...

UHMW is expensive. It makes good budget nuts for your leadscrew. Don't use steel nuts. What were you thinking for lead screws?

I know MDF gives many people a bad taste in thier mouths, but it is quite flat, stable, sturdy, and heavy. It's better than plywood for our use.

Paint it gray and it looks like steel plate. :) Most people who saw my first machine IRL (in real life), thought it was made from 3/4" boiler plate.

Aluminum is better, but like you say, hard to work. Save aluminum for your next machine.:)

Eric

Mike,
>>did he just capture the rails in a bore in the sidewalls
Yes.
Take note that the machine is like 'proof of concept' thus it does not have the accuracy & rigidity like other members' homebrew.

I did some modeling this morning, trying to capture some of the basics... So using 3/4" MDF, here's what I came up with...

Using 3/4" and 1/2" drill rod, I used 36" lg for the x axis, 24" long for the y axis and 12" lg for the z axis. This is so I can buy off the shelf drill rod and not have to cut it to length.

That gives me the following allowable travel:
x = 28 1/2"
y= 16 1/2"
z= 7 1/4"

Oh yes, distance under gantry = 3"

Am I headed in the right direction? What do you guys think?

Mike...

P.S. Check out the attached picture...

Here's another picture...

I made the base lower, increased the distance under gantry to 4.5, added the stepper motors, the 1/4" thd rod and also some anti-backlash nuts.

Does anyone have the basic dims (or a solid model) of a router, like the porter cable?

Mike...

Keep in mind that the router needs to reach the table. This means that the "plate" on the z axis needs to extend beyond the bottom bearing a distance equal to the distance under the gantry. Also its nice if this can be retracted to a point where the extention clears the bottom of the gantry when fully up. It's often handy to make this part from a chunk of aluminum, since it's a bit more rigid. if you use MDF, you need to make some gussets etc.

Eric

Something like this?

Mike...

I made mine out of baltic birch, with some gussets for extra strength.
http://www.cnczone.com/showthread.php?s=&threadid=1356&highlight=another+first+router
It's a little heavy, but it's pretty stiff. Holds a Porter Cable 690 or the new 890's. I'll actually be using an 892 that I just got.

Gerry

Yes, just like that. Perhaps you can get away with a little less because you only need the collet of the cutter to make it to the table.

Eric

Hey Gerry,

That thing is built like a tank! Wow. But the baltic birch looks good!

Mike...

I am acquiring the components to build a router capable of having a 24" x 36" working area.

I've noticed many CNC wood router designs have the gantry move in the X-axis, while others have a fixed gantry and the table moves in the X-axis.

With the gantry moving the overall length can basically be shortened in half of what would be required for the same work size as a moveable table.

What are any other advantages/disadvantages to either design?

Great minds think alike :D

Hey Sol,

I like that. Do you have some close up pictures of the end of the pipe? What kind of bearings are you using? How about your anti-backlash nut...

And what size is your table top?

Mike...

Hey dlenox,

That's a good question... I don't know the official answer, but I can tell you what my gut feeling is...

I don't want the material to move. That way I can also machine a piece that's twice as long as the table, and do it in two steps.

You can't do that if your table moves.

Your machine will be almost the same size as mine. So what are you going to buy for
1) linear shaft
2) bearings
3) ball screw or thd rod
4) anti-backlash nut

Mike...

Dlenox
It is easier to build a fixed gantry so that it is solid with no shake, rattle and roll, but as you stated the price is the extra floor space lost by the moving table, as well as Mike's observations about size restrictions of cut.
Mike
A more detailed show and tell is here, http://solsylva.com/cnc/cnchome.html but as Abasir said about his table, mine is just a ‘proof of concept' as well, crudely made with shop jetsam.

Moving gantry has a smaller footprint, is a little more complex, and is not quite as acurate.

Moving table is larger, slightly simpler, and more acurate.

E-man

got some good advise from others in this group! thanks

I plan on using the following:
1" drill rod for the X-axis, using round linear bearings
obtained 20mm rectangular linear bearings for Y-axis from Ebay
today mounted on extruded alumuminum
use 3/4" drill rod for Z-axis, with round linear bearings
using 1/2-10 acme threaded screw all around

Still have to decide on fixed vs moveable gantry...
Lots of decisions

Balsaman,

What do you call accurate?

I plan on cutting 3/4" oak plywood in one pass and hope to achieve <= 1/64"

If you build the machine nice and tight you will be fine. The problem comes in when you are cutting close to the side of the gantry. The screw is in the middle, so the gantry wants to skew. I would consider making the gantry sides wider, so that there is more space between the guides. The moving table scheme eliminates this problem because the guides are spread way out at the corners of the table.

Eric

Sol,

Thanks for the link. I really like the wooden bearing mount part. I think it can be made easily with aluminum. Any foreseable shortcomings?

Sol,
This is a super "out of the box" design. I especially like the alternative tension adjustment.

Hager

sol
I like the idea of "dumpster diving" in your own shop. Nice proof of concept too. Just wondering what sort of "accuracy" you get? Precission and repeatability would be a nice reference to lay alongside overall cost. Could you provide here, in a PM or on your site?
I say congradulations - your results should certainly make others getting started less intimidated.
:cheers: Jim

Sol,
How about posting your machine on a new Thread? All new machines deserve it.
It helps future builders go back and look at the design for ideas.
Hager

How does one measure precision and repeatability?

Do I just use calipers and measure something?

Mike...

I've seen a number of pictures where the stepper motor has a belt drive to the ball screw/thd rod.

What's the benefit or disadvanted of using a belt drive. I was going to have a direct drive on mine, with a fixed coupling between the axle shaft and the threaded rod.

Can someone tell me which way is better?

TIA

Mike...

For a DIY "cheap machine" I think direct drive is the way to go with stepper motor. Its a good example of the KISS principle.

I feel that the timing belt gear reduction is better suited for servo drives where you want to keep the speed of the servo up and gear down the turning of the lead screw.

Answering your other question about measuring precision and repeatability, I make a test program and have the router make a test part, say a 10" square or 10" circle. I then measure the piece and record my measurements. If you make 100 parts and they are all 11" exactly, then you can say that your machine is very repeatable, but not very accurate.

How accurate you want it to be depends upon your needs. +-.004 per foot sounds good, but that is +- .032 over 8 feet. Is that good enough? Only you can decide.

Another way to check is to put a dowel in the collet and jog the machine to a known coordinate. Then measure the distance against a solid surface, The machine itself, a wall, etc. Jog the machine again and measure again. You can use calipers, tape measure, dial indicators, or a string with knots in it. Again it all depends upon you needs.

Personally, I use digital calipers dim's under 6". a dial indicator for checking flatness of the table, and a tape measure for long dimensions.

>get the 116 oz steppers from Xylotex


Hey Balsaman,

Why wouldn't I get the bigger nema 23 stepper, i.e. the 253 oz? Isn't more torque usually better? Especially if I want to hog out more material at one pass...

Mike...

http://www.pacsci.com/products/step_motors/powermaxproducts.html

Can someone illustrate to me typically how the lead screw(s) are retained?

I assume that this allows the screw to rotate within the bearing which is fixed but not allow the screw to move laterally in either direction by "sandwiching" it between washers/nuts and having a retaining plate hold the whole thing in place?

Also assume that the other end has another bearing to support that end as well, then connected to the step motor using a coupling?

Well I can certainly illustrate what I see!!!

In the picture below, you see the coupling that connects the motor shaft to the threaded rod.

The lower shot is where the threaded rod goes thru the anti-backlash nut.

The other end just hangs there in space... in a 2 1/4" clearance hole actually. I might be inclined to capture that in some fashion to keep it from whipping around...

Mike...

I wasn't going to include a picture of the hole... but what the heck...

Here it is...

Mike...

Originally posted by mikeschn
>get the 116 oz steppers from Xylotex


Hey Balsaman,

Why wouldn't I get the bigger nema 23 stepper, i.e. the 253 oz? Isn't more torque usually better?

Because they cost at least 4 times as much, unless you can find used ones. And for what Jeff at Xylotex charges for them, you won't be losing much if you upgrade later. On that note, On the Xylotex group Jeff said he probably won't be selling them for much longer, so get them while you can. As for the 253 oz, I got 4 last april on Ebay for about $60 each, but haven't really seen any since.If you can find them for a good price, or don't mind paying, get the bigger ones.

Gerry

>How accurate you want it to be depends upon your needs. +-.004 per foot sounds good, but that is +- .032 over 8 feet. Is that good enough? Only you can decide.

Hey buscht,

Really? out by that much? So when you hear someone talking about a +- .0025 tolerance, they are really talking about the stepper motors, not the completed system, right?

The completed system would have to be parallel and perpendicular so that you are not out by .032 over 8'.

Mike...

Oh Balsaman,

Jeff no longer sells the motors. He recommended some guy on ebay... see this auction... 2586416419

It's currently at $81. How much do the 116oz motors go for normally?

TIA,

Mike...

I think he was selling them for $20.00? You can always wait. Lot's of steppers on ebay. You want 5 or 6 volt ones.

200+ oz is is nice and quite manly, but expensive and hard to drive. xylotex only drives 2.5 amps MAX. You need Geckos after that. $375.00 for 3. On a wooden machine you should not be "hogging" anything. 100 oz in steppers will do more than you think. I was using them and could cut up to 3/8" deep in one pass at 20" per minute.

.032" is 1/16 of an inch, over 8 feet, that will do for most hobby people. We usually make trinkets after all. :)

Eric

Mike,

thanks for the pics! just what is an anti-backlash nut?

With the stepper motor turning to push/pull the gantry I would think that it would be better not to put these stresses onto the stepper motors. I would think that a better design is to support both ends of the screw...

Actually, .032 is 1/32", but you already new that :) Those motors on Ebay are the same one's Jeff was selling. He was buying them from the same guy. He must have a million of them, because he always has some for sale. Depending on the time of the year, they go for anywhere between $60 and $120 (for 4). If you want new ones, here's a place you can order from online (with prices).

http://new.kimcontrols.com/category/Step_Motors_NEMA_23/man/5/Pacific-Scientific

Gerry

Hey dlenox,

Here's a good illustration of an anti-backlash nut...

read all about it here...

http://www.wmberg.com/article970324.html

Mike...

Hey Ger21,

That's perfect... now I can find my 116oz step motor... hmmmm the list doesn't give me oz. It doesn't give me amps either... I need to know what those part numbers mean... Maybe you or balsaman can help me out. What part number am I looking for?

All I know it it's gotta be a nema 23, 2.5 amp to work with the Xylotex, and you recommended 116oz for the price.

And I should be looking to pay about $20 or so on ebay?

Mike...:confused:

Originally posted by ger21
Actually, .032 is 1/32", but you already new that :) Those motors on Ebay are the same one's Jeff was selling. He was buying them from the same guy. He must have a million of them, because he always has some for sale. Depending on the time of the year, they go for anywhere between $60 and $120 (for 4). If you want new ones, here's a place you can order from online (with prices).

http://new.kimcontrols.com/category/Step_Motors_NEMA_23/man/5/Pacific-Scientific

Gerry

Yes, I meant to say "half of 1/16th"

You need to support the other end of the rod. The motor bearing cant support the load, plus there is tons of backlash in the motor. The free end needs to take the load. Most folks capture a bearing on the rod with nuts and mount the bearing against the machine with a large washer, drilled for screws outside the bearings outer race.

E-man

Originally posted by mikeschn
Hey Ger21,

That's perfect... now I can find my 116oz step motor... hmmmm the list doesn't give me oz. It doesn't give me amps either... I need to know what those part numbers mean... Maybe you or balsaman can help me out. What part number am I looking for?

All I know it it's gotta be a nema 23, 2.5 amp to work with the Xylotex, and you recommended 116oz for the price.

And I should be looking to pay about $20 or so on ebay?

Mike...:confused:

Sorry, I got no part numbers. Look for 5 or 6 volt, nema 23, ~1.5 to 2 amps.

Eric

Balsaman,

This is what I think I heard you say... would you eyeball this picture, especially the captured bearing on the left and tell me if this is what you were trying to describe...

Thanks,

Mike...

Download this:

http://www.pacsci.com/support/documents/stepper/stepsel.pdf

Page 41 explains the numbers, 48 and up list available types. You're not going to buy new ones are you? If not, buy the ones from Deepgroove to start with, unless something better comes along.

Gerry

Yeah, that's what he was talking about.

Gerry

Okay Ger21, Got it... I'll print it out tomorrow at work. Its quite the document!!!

And yes, I'll get em from deepgroove1. I've already started the email discussion with him!!! :-)

Mike...

Don't print the whole thing, you only need pages 40-54. Those motors are rated at 3.5a when wired parallel, and 1.75a when series wired. Jeff at Xylotex has recommended running them at 2.5a wired parallel. Although you won't get full torque that way, you'll get better high speed performance. I recommend reading all the messages on the Xylotex group for more info. I don't think you'll find a better deal than those, btw.

Gerry

Originally posted by ger21
Yeah, that's what he was talking about.

Gerry

Ger21,

Now I am really lost... that arrangement on the left looks like a combination bearing and anti-backlash nut.

Why is that bearing needed, if there are bearings on both the top and the bottom guide rails?

The threaded rod is not supporting any weight. It is only supplying axial torque.

Please advise...

Thanks,

Mike...

It's to basically hold the leadscrew in place. All the weight and force of your motor pushes and pulls the leadscrew, and steppers aren't meant to hold it still, and have too much play. So you need to mount the leadscrew at one or both ends to take those thrust loads without moving. Does this help?

Gerry

Originally posted by ger21
and steppers aren't meant to hold it still, and have too much play.
Gerry

Ah, gotcha... I didn't realize steppers had that much play in them... okay, I'll design accordingly!!!

But then what is the bearing for?

Thanks,

Mike...

On bigger machines, that is an angular contact or thrust bearing. It takes all the axial loads of the leadscrew. take a look here:
http://www.5bears.com/cnc04.htm

On smaller machines, you can get away with regular bearings (rollerblade are probably the cheapest). Even though they're not made for axial loads, they can handle enough for what you'll be using it for. Make more sense?

Gerry

Originally posted by ger21
On bigger machines, that is an angular contact or thrust bearing. It takes all the axial loads of the leadscrew. take a look here:

Gerry

Ouch... you've turned my brain into mush...

Okay, thinking about a thrust washer, I drew this up. Basically the two jam nuts capture a washer which then press against the thrust washer when loaded in that direction. Is that what we are trying to accomplish?

So then back up a few messages to my original sketch. By fastening the big washer to the side of the gantry wall we can take the thrust in both directions? I'm missing something...

Tell me more about that bearing. Is the inner race flush with the outer race? or is one offset from the other? Let say the axial load is to the left, the outer race takes that load? Then when the axial load is to the right, the inner race takes that load?

I better get to bed... maybe my brain won't be so mushy in the morning. Of course if you wanted to make a sketch of your own showing how that bearing works, that might be a big help... :D

Mike...

So then back up a few messages to my original sketch. By fastening the big washer to the side of the gantry wall we can take the thrust in both directions? I'm missing something...

Thats it. You attach the bearing to the gantry (in this case), and all the thrust (both directions) is taken up by the mounted bearing. The only loads the stepper will then see are the radial loads.

Gerry

Man you guys post fast. The original drawing you did was about right. The nuts have to be agaist the bearing. The hole in the washer that retains the bearing it needs to be larger than the nut, so the nut can spin inside it against the inner race. The outer race gets held against the MDF by the washer with bolts/screws. Now the bearing is held in place. So is the lead screw. The screw can turn freely but not move axialy.

E-man

Duh, I think I got it! ;)

We use the jam nuts to capture the inner race, effectively making the inner race a rigid part of the shaft.

Then the large washer captures the outer race against the wall of the ganry.

And the radial bearing becomes the thrust bearing.

And off to bed I go! :D

Mike...

Originally posted by balsaman
The original drawing you did was about right. The nuts have to be agaist the bearing. The hole in the washer that retains the bearing it needs to be larger than the nut, so the nut can spin inside it against the inner race. The outer race gets held against the MDF by the washer with bolts/screws. Now the bearing is held in place. So is the lead screw. The screw can turn freely but not move axialy.

E-man

Hey Balsaman,

When I made the original drawing I thought the nuts were capturing both races, which is why it didn't make any sense.

But I drew that last sketch up laying in bed... probably while you were out here composing your email. And as soon as I opened up the diameter of the washer it all made sense. !

And thank you so much for your last email. It confirms what I was finally thinking.

Tomorrow the saga continues!...

Mike...

Mike...

You got it!

Eric

where is a good source for anti-backlash nuts?

Originally posted by dlenox
where is a good source for anti-backlash nuts?

Why can't we make our own? Here's an idea I am toying with...

http://www.phillycast.com/products/superalloy.htm

Mike...

Mike,

certainly could, I have a mini-lathe and mini-mill, however I feel that my time could be spent better if certain items were purchased.

Cutting outside threads is pretty simple, but I am pretty rusty when it comes to inside threads...

You don't cut internal threads. You drill a hole, insert your threaded rod and then pour that superalloy stuff in, and let it set.

24 hours later you break it loose, and voila', a perfect thread, with no backlash!!!!

Mike...:D

I am ready to buy the 3/4" and 1/2" shaft for my cheapCNC. I've found some sources, including e-bay... but what is the best material to buy

I'd like to buy un-hardened ground steel shaft, it seems to be the biggest bang for the buck. Will that work?

Or do I need hardened shaft? Why?

One supplier didn't have the length I needed, in steel, but had it in Stainless Steel. Will Stainless Steel work?

TIA

Mike...

I wonder if the superalloy could be used for bearings? i.e. drill rod the size needed. Mike why don't you start a new thread. Know how much this stuff costs?

Phil

If you're using linear bearings with balls in them, I think you'll want to use hardened shaft so the balls don't wear grooves into the shafts.

Gerry

Phil,

I really have to do some searching... Just as an example, I went to Stock Drive Products and this is all they had in 3/4" shaft. I could not find hardened carbon steel there. :-( But there is a big difference in price between these two...

3/4" precision drill rod (unhardened) 36" long = $37.58

3/4" case hardened stainless steel 36" long = $81.56

Mike...

P.S. Do you have any good sources for drill rod or shaft? (besides ebay)

Enco has it on sale all the time:
http://www.use-enco.com/CGI/INSRHM look at their hot deals catalog

right now 3/4 oil hardened is $8.29 each water hardened $6.49
you can get 1" oil hardened $13.99 water hardened for $11.09

also look at the price on their 1/2"-10 acme rod 3' is $3.49 6' = $6.99

the 1/2"-10 acme nuts are $.99

Look at my webpage start

http://webpages.charter.net/pminmo/mycncpage.htm at the bottom is reference to some items that make good sense.

McMaster-Carr has 3/4" precision hardened, 36", for about $35.
As for the $3 acme, If your spending several hundred $$$ on your machine, I'd rather spend 20$ for precision acme leadscrews than 3$ for cheap acme rod. Just my opinion.

Gerry

the Enco cheap-o acme rod is pretty rough. Good for making clamps and stuff. Not good for CNC machines. I tried it and it sucks.

I got some precision rolled acme rod from Kerk Motion and "Woah" what a shocker very nice... they are very nice. I had no idea that acme rod could be that nice.

Boils down to cost vs accuracy. IMHO if it's built out of MDF, you can get by with the cheap stuff. If your going to build a nice metal frame, have the time and toold for high accuracy, then I'd agree. I was under the impression he is looking for cheap. There are a number of wood routers built here with the cheap acme rod.

Ah yes, the first machine I build I was planning on building "cheap". Trying to get some experience under my belt.

Then I want to use my first machine to cut a new machine out of aluminum. So the first machine has to be reasonably accurate. How accurate is that? I figure it need to be able to properly locate and cut nema 23 mounting patterns. It should be able to cut bores for a close slip fit with the x, y and z axis bars.

I don't want to use black pipe with roller skate bearings. I want more precision than that! So I figured I would use hardened and ground steel rod, if I could find it for about $35.

My next machine, btw, will use those ground rod bolted on top of a rail or beam. Any idea where I can find that?

Mike...

Don't start thinking about the second machine, finish the first one. Everything will fall in place.You doing great. Stay focused.

Originally posted by anoel
the Enco cheap-o acme rod is pretty rough. Good for making clamps and stuff. Not good for CNC machines. I tried it and it sucks.

I got some precision rolled acme rod from Kerk Motion and "Woah" what a shocker very nice... they are very nice. I had no idea that acme rod could be that nice.

Agree. Cheap-o acme rod I bought was slightly bent. It whipped over a few hundred rpm. Bought some precision ground acme from Mcmaster Carr, that's nice stuff.

MDF is great stuff. Can be drilled and tapped, and screwed together. Paint the edges with watered down wood glue, and they will take paint better. You can buy all kinds of plastic stuff at www.smallparts.com. UHMW is quite thermal sensitive, especially in thin sheets. Sometimes warping 3/4' or more over 2 or 3 feet! Check out this design for a bearing holder, http://www.buildyouridea.com/cnc/hblb/hblb.html, hopefully I will soon be offering something similar. 5/8"-10 acme screw can be had for $10 for 6ft from www.use-enco.com.
Cheers,

I got some precision rolled acme rod from Kerk Motion and "Woah" what a shocker very nice... How much did it cost? I checked out thir website but no prices. I think it is an excellent product for my needs.

How do you guys do it?

I tried cutting a few parts out of MDF using manual methods, clamping two parts together so holes would line up, etc... and still my parts are off by a little bit. :-(

So now I am using a cnc router to cut my first machine. And it's a really slow process. Accurate, but slow. Like 6 IPM slow. But the pieces are looking sweet! Hope to have some photos for you in the next couple days.

There is ice and snow in the forcast... if it gets bad I get to go home early. (That is, I get to cut more parts!!! :D ) Hopefully I'll have my x axis done, with the gantry riding on it in the next couple days!!!

Mike...

P.S. Did I get the names of those assemblies right? i.e. the base, the gantry, and the bridge?

You could make a template piece out of MDF, then use carpet tape to tape it to your parts, and use a flush trim bit to route it flush. You can make as many identical parts as you want this way. And when drilling your holes, carpet tape the 2 pieces together and use a drill press.

Gerry

You get to go home for 2" of snow? I work in Livonia and live in Shelby Township and it took me 3 hours to get home from work 2 weeks ago when we had that big snowfall.

Gerry

I live in Lake Orion, and work in Warren. That day when it took you 3 hours to get home, I bailed out 1/2 hour early, and it only took me 2 hours.

I'm keeping an eye on the current storm, and plan on bailing out if it means I can beat the rush. You live in the area, you know how the roads can clog up with just a little snow on the roads.

Anyways, if Tuesday morning is really bad, I'd rather stay home and cut parts. You know, the excitement of building your first machine!!! ;)

Mike...

Here's the problem. First I got the end pieces of my base made, which by the way had 3/4" holes for the shaft. Then I went to cut out the sliding gantry plates. The holes had to be in the same location, but the hole sizes were larger. (1 1/4" for the bearings). To make matters worse, the sliding plates were a different size than my end pieces. No way to line anything up. :(

Mike...

Originally posted by ger21
You could make a template piece out of MDF, then use carpet tape to tape it to your parts, and use a flush trim bit to route it flush. You can make as many identical parts as you want this way. And when drilling your holes, carpet tape the 2 pieces together and use a drill press.

Gerry

Attach the 2 pieces together like I said, and drill the smaller hole all the way through both. Seperate the 2 pieces, and then take the one that needs a bigger hole back to the drill press. Use the small bit to align the hole, and clamp the part in place. Switch to the larger bit and drill. The holes should be perfectly lined up. This works best with forstner bits.

Gerry

You know, I think you're onto something...

What if I made all 4 plates the same size to start with. Drill the holes as you suggest. Then go back to the tablesaw and cut the 2 down to the right size. As long as I take an equal amount off on each side, I should be fine!

Sounds good! Bring on the ice and snow!!! :banana: :devious:

Mike...

Mike,

Here's a very accurate way to make the larger holes.

Use a router bit with 1/4" overhang of the bearing. A 1/4 rabbetting bit, for example. Whether the bearing is above or below doesn't matter; only that it cut bigger than the bearing by the exact amount you need to enlarge one "side" of the hole. You can use magic brand scotch tape toadjust the bearing size if necessary. Be sure to start and stop the tape at teh same place; no overlap "bump"

Drill the 3/4 holes with the parts fixed together, going through both. Then use the router bit to enlarge the "bigger" hole PART WAY. The shape of the bit doesn't matter really. What you are doing is making a 1-1/4 diameter for the next step...

Which is to use a flushcutting trim bit to make the whole wall straight and 1-1/4 overall diameter.--you did only part of the depth with the 1st bit--

FWIW, I like spade bits for the 3/4 hole. because you can easily file them to adjust the hole to tightly fit your rods. (And if you go too far, a spade bit is only a few bucks. So you can either buy a new one and file more carefully, or you can hit the one you have with a hammer to spread the metal and file some more :)

Hope this helps,

Ballendo

Here's how I made my custom sized spade bits.

Put the bit in my drill press, made a MDF (what else) fixture to hold my right angle grinder. It was then bolted to a piece of MDF the same size as my drill press (DP) table so that it pivoted into the drill.
Turn the DP on and slowly pivot the grinder until it touches, lock it then slowly raise and lower the spade bit grinding the edge evenly.

Since there isn't any scale or reference marks it took me three bits before I got it right. But it works and fairly safe.

One thing I did notice about the spade bits, they have flats ground on them at the factory, the flats are not that accurate to the dit shaft. It would have been better if they were round.
Hager

Originally posted by pack rat
How much did it cost? I checked out thir website but no prices. I think it is an excellent product for my needs.

Pack_Rat,

You've got to call and talk to a sales rep, I was gritting my teeth waiting for a quote, I only ordered a 12" 1/4"-10 teflon coated screw and A-B nut this time around (Taig Lathe conversion) 1/4" is as big as I can go on that machine comfortably, and that was like $36 shipped. They have a $50 min order, but they let me slide on it.

It's not exactly cheap but it certainly won't break the bank