My first build. Bearing Proof of Concept

[(Wayne)]

I have wanted a CNC router for many years but haven't been able to afford one. I started reading up on building my own about a year ago and I'm finally getting started. This will be a slow process and for my first build I'm mostly interested in learning the mechanics and how everything integrates. I have decided to base my machine on the Microcarve design, but with a moving gantry.

Tonight I put together what I consider a proof of concept for my linear bearing system. I like the bearing set up of the Microcarve, but don't have the machinery to achieve the press fit.

I purchased T416 stainless 3/4 round rails and oilite type bearings. The oilite bearings have an OD of 1". This is slightly smaller than the ID of 1" pvc. So while I was walking the isles of Home Depot trying to come up with a solution for securing the oilite bearings, it hit me.






Using my table saw I ripped a slot in one side of the PVC and was able to use a hose clamp to secure the oilites in place. I don't think the hose clamps will end up being the solution used, but it work quite well.


I am waiting on my Acme lead screws to arrive, but hopefully I can get the frame together in another week or so and see how well this holds up.


Comments and suggestions are welcome.




-Wayne

[microcarve]

I have wanted a CNC router for many years but haven't been able to afford one. I started reading up on building my own about a year ago and I'm finally getting started. This will be a slow process and for my first build I'm mostly interested in learning the mechanics and how everything integrates. I have decided to base my machine on the Microcarve design, but with a moving gantry.

Tonight I put together what I consider a proof of concept for my linear bearing system. I like the bearing set up of the Microcarve, but don't have the machinery to achieve the press fit.

I purchased T416 stainless 3/4 round rails and oilite type bearings. The oilite bearings have an OD of 1". This is slightly smaller than the ID of 1" pvc. So while I was walking the isles of Home Depot trying to come up with a solution for securing the oilite bearings, it hit me.


Using my table saw I ripped a slot in one side of the PVC and was able to use a hose clamp to secure the oilites in place. I don't think the hose clamps will end up being the solution used, but it work quite well.


I am waiting on my Acme lead screws to arrive, but hopefully I can get the frame together in another week or so and see how well this holds up.

Comments and suggestions are welcome.

-Wayne

EX-cellent Idea!....

The clamps should work pretty well....or maybe even saw-split a PVC coupling
and glue it in place over the assembly you have. With the new split
on the opposite side. It may get a little thick with 2 layers of PVC. though....

Very Cool thinking!

John

[adprinter]

Wayne,
The design you have pictured here might be fine for building something like a paper trimmer table, or something similar. However, for CNC you want to go with some type of bearing assembly. Ultimately, once assembled onto your rails- you should be able to give your gantry (or table- not sure which you have in mind at this point) a gentle push, and it should glide from one end to the other. Anything LESS than this type of performance, will require motors which might approach the strength of a car engine to drive your slide mechanism. I don't want to discourage you, as I was once where you are before building my first machine. But I am assuming here, that you want your CNC to be able to actually CUT something (or engrave, or whatever). The forces that are exerted on the rails/sliding mechanisms of your machine are heavy. Even for a small machine driving something like a Dremel tool. You want precision in your design, and everything should be riding on at least ball bearings so that it is able to glide smoothly. While those bushings may glide on the shafts, by simply sliding them along the shaft, try grabbing just one end of it and pull up on it while pressing down on the opposite end and see how well they glide. This is the type of force that will be exerted on them, if used on your CNC machine.

[(Wayne)]

Thanks John. I have learned a lot from reading your posts and studying your machines.


Adprinter,

Thanks for the input. Right now I am brainstorming and trying different things. This build is a learning experience for me. So if something doesn't work I will change it. I like the idea using oilites because they are simple and cheap and they seem to work very well for John's machines. I am just trying to figure out how to use them without be able to press fit them into the pipe.

I have another idea that I think will work better than the hose clamps. Hopefully I will have time to work on this tonight.

I don't know how accurate this first build will be, or if it will work at all. But I do expect to learn a lot from it. That is what I enjoy.

[microcarve]

Thanks John. I have learned a lot from reading your posts and studying your machines.

As you've noticed, Oilites come in different thicknesses. It's a general
PITA to do, but they can be pressed onto a wood dowel and stuck
in a drill press and filed down while spinning to fit into some PVC tubes.

It can work, but it's such a PITA and a few bearings can get ruined, but
I have done it before. Still, I hesitate to even mention it.


John

[cyclestart]

It's a general
PITA to do, but they can be pressed onto a wood dowel and stuck
in a drill press and filed down while spinning to fit into some PVC tubes.

A possible work around for mini lathe owners with 3/4" thru-hole ? The PVC tube is too large ?

Still, I hesitate to even mention it.

warning noted

adprinter
the oilites appear to work very well if alignment is dead on. They won't tolerate any misalignment (been there, done that, have the junk parts to prove it)

[microcarve]

A possible work around for mini lathe owners with 3/4" thru-hole ? The PVC tube is too large ?

Good question....

The bore in my 9 x 20 lathe is too small too. I make the tubes with it
extended out from the chuck.

What I do have going for me is that I have variable speed, so it doesn't
spin so fast that it's dangerous to work it with the tube extended out
like it is....but any lathe can be slowed down well enough. I stick with
about 6-8" max. length.

Just get the tube spinning. Bump it with your hand a few times, and
it'll spin as true as it'll get. I use a rough mill file to square up the
end while it's spinning....(much less deadly than it sounds...

Then bring the reamer close the the tube end and bore it.

But...I did have to customize the reamer too. It wouldn't fit in the
tailstock. Had to turn the shaft down to 1/2". Big PITA as the shaft
is Really hardened. But mine is a dedicated tool strictly for making the
tubes.

I'll have to admit, the tubes are a pain to make. They're pretty easy
for me now, and I can make some available for anyone who may want them
a little later.

The main problem is the reamer. It does a perfect job in 5 seconds. But
buying it and turning it down isn't worth it for a handful of tubes. I didn't
have a lot of luck so often before I modified the $$ carbide tipped reamer.


John

[microcarve]

.

I tend to think in terms of the 5/8" shafts I use...and reproducing many of the
tubes....

But...Silver & Deming bits can work fine. They can bore amazingly precisely.
And, the 1/2 shaft can fit a lathe tailstock chuck.

Extended out from the chuck like that works well, but I don't
use the cross slide for squaring the ends....a rough file works well because
it presses the tube towards the spinning chuck and it won't fly out...unless
someone is a little too rough with progress....

The 7/8" O.D. bearing fits with a press fit.

It takes some trial & error and a few mistakes, but the bearing tubes
can align extremely well. The roundness of the bore matters. The tubes
themselves aren't round inside or out.

But, they're intended for cheaper home built machines... not precision
aerospace instruments. They get glued to some MDF and the glue seeps
into the MDF and the bearing won't break off without someone intentionally
trying to do so.

The glue seeps around the irregularity of the tube roundness and fills
gaps. So, overall, it aligns Extremely well and with care the tubes
can slide glass smooth.

BTW...that's a 3/4" PVC tube. Boring a 7/8" hole into it. Confusing?...


John

[mmonti]

Ive been messing around with making alot of these bearing tubes and I found another trick to help with alignment. Im making 4 inch slides with an oilite at each end

After you have bored/reamed the pvc, and pressed in the oilite (doesnt take much to press them in, I can get it started by hand then flip it over and lean on it, and it seats completely) put it on your shaft, it will most likely bind at least most of mine do , get out your propane torch and gently heat up the pvc by waving the torch back and forth quickly, it gets soft fast so be careful. Dont distort the pvc with the heat or it will be harder to glue it to the mdf. I use a gloved hand and gently slide the bearing tube when its warm/hot and the oilites magically align and it cools in its new position. My best set of bearings were made this way. I also used a stick of pvc trying to make bearings ymmv

Hope this helps someone

Mike

[(Wayne)]

Lots of great ideas.

I didn't get a chance to work on anything tonight, maybe tomorrow.

, and I can make some available for anyone who may want them
a little later.

I may take you up on this, If I can't come up with a reliable solution.



-Wayne

[rocketflier]

Using my table saw I ripped a slot in one side of the PVC and was able to use a hose clamp to secure the oilites in place. I don't think the hose clamps will end up being the solution used, but it work quite well.

-Wayne

I'd be surprised if JB weld didn't do a good job of filling the crack and holding the pvc closed without the clamp. At least until it was attached to the sled.

I was in lowes the other day and found some closet rods that are fairly heafty:

8' chrome $23
6' nickle $20

But they're 1-5/16". There was a thin wall 1" sort of hidden that I couldn't tell how thick the wall was (but it was much lighter). This one on-line says 'solid' which would be a lot heavier

8' nickle 1" $20

Not sure if any of those would be dimensionally accurate {enough} for a benchtop?

[(Wayne)]

My other ideas didn't pan out as I had hoped. So I have decided to buy a lathe. I have been wanting one for quite some time so now I'm going to get one.

After tons of reading and watching just about every lathe video on youtube, I think I have decided on the Grizzly G0602. It will probably take a month to save for it, but I am excited about it.