a cheap linear bearing

[mocnc]

Ok, I know there are a lot of very smart ppl here, and I was wondering if I may ask for your help. I know I am not alone in this question and we really do need help with it. If any one of you have an idea for a linear bearing using the roller skate bearing please let me know as well as all the others that are need of this help. Something that is simple to build and doesn't cost alot to build. I am using 1/2" black gas piping for my cnc. I know it is something that most of you don't use but it fits in my budget, the budget that the wife has allowed lol. I know there must be alot of you that are in my same kind of boat that I am. I don't have a lot of money to spend at this time, with a wife and 3 kids growing like wild weeds........but in the future I will make the 2nd much cnc better. So please bare with me and all the other newbies out there that for what ever reason can't come up with a descent idea for a roller skate linear bearing (in other words a cheap linear bearing). Call it a brain fart, or inexperience, or a lack of know how........or hell even just plan lazyness, what ever; but please have a heart and help out. I have been lurking around in this community for a little while now and I have seen how generous and how intellegent this community is, and I hope to....no I will one day add back to this community. But for now I can't. Not because I don't want to, but for not knowing how too.....but for a lack of know how. I lack the experience and knowledge of many of you. So I guess I need to ask if you can post your ideas on a cheap linear bearing using the roller blade skate bearing. Any and all ideas would help! Maybe with all the ideas posted to one area we can come up with one great idea! Thank you all so much. Btw, I said all those nice things not to get a responce but to truely thank everyone who has helped our community, but most of all to thank the administrator/owner of this site for all their help and work. If I don't even get a responce back, or a responce that has the info on a bearing design, I will not be upset because what I have said I do really mean! This is one hell of a great site!

[Hasher]

hi mocnc

I have been looking at using Ball Transfers myself. Take a look at page 1083 of
mcmaster catalog or search "Ball Transfer" , there website is http://www.mcmaster.com/.

I am looking at using the "ball down" method but it your using pipe as a rail you could use the "Transfers at an Angle" method as described on page 1083


Just some food for thought

Paul

[jcc3inc]

Sir,
I have attached a couple of pix of a machine which I built as a Test Bed for the software I'm making. It is built with the idea of keeping the ddesign simple and parts cost low, while making a stiff machine. You can Email me for more info.

Regards,
Jack C. jccinc-at-owc-dot-net

[pminmo]

jcc3inc,
I suspect that you have hit on a very good solution. My understanding is most crs has pretty good tolerance to start with, at least as good as gas pipe. As shown it's very well supported so as not to deflect under load. Edge's could be fine tuned if necessary.

Phil

[coolman]

jcc3inc,

I plan to make something like what you have in the pictures. I have some questions. The position of the bearings is depended on the hole that is drilled through the metal piece. How do you get the hole locations exactly such that the bearings fit tightly to the flat metal support? Or, is the hole big enough to allow for some adjustments.

Also, can you give me some general guidelines on how to make such a bearing?

What size bearings and what kind did you use? Can you post a closeup on your bearings?

What about your Z axis bearings? I would like to copy that method also.

[sol]

Mocnc,
You want cheap?
Doesn't get cheaper than this...
http://solsylva.com/cnc/cnc5.html

[jgro]

Hasher,

Don't bother with ball transfers. I tried it a couple of months ago and it didn't work very well. The balls will skid across the round rod rather than roll. Just letting you know my experience.

jgro

[mocnc]

Thanks to all of you for posting your ideas or help. There are 589 views to this topic since I posted it 4 days ago, so there is an interest in this. Looks like a big interest. From my guess now there has to be alot of ppl in the same situation I am in. I realize not all 589 ppl are looking for the same thing, but out of that number we can take a large amount. I hope others post there ideas, no matter how simple or stupid they think it is. Once an idea is out in the open others can look at it and run with it. They can take the idea and make it a starting point for their new and improved idea. Hell, maybe into a whole new direction from the original idea but having the same ending we all are looking for. Others may not have had the original thought, the the final outcome is what we are all looking for. BTW jgro, I always wanted to say thanks for all you have done here at cnczone. You have given alot with your free cnc design!

[jcc3inc]

Sir,

On my particular machine, I used bushings from Bishop Wisecarver to fit my bearings; the bearings are .375 ID, .875 OD, .28 wide. Bushings are available in eccentric and non-eccentric varieties, so you can use them to adjust the preload on your ways, and to adjust squareness of the cross rail to the main rail. Other sizes are available.

My long axis ways is a cold drawn flat; three bearings each are used front and back on the main frame. On the cross carriage I have used a similar setup. The particular flat I used on the main rail is +-.001 overall variation; the cross rail setup (1/4 x 4 inches) is similar in tolerance. You should be reminded that these tolerances are likepy not guaranteed, however. In one case where we used cold drawn flats on a commercial machine, we had a case where the straightness of one end of a 12 foot piece was at least 1/8 inch off from the rest of the piece. One should make a stiff frame to which the rail stock is attachged, and plan to use shims to obtain the straightness which you need.

My Z axis uses V rails from Bishop Wisecarver and their Vee wheels; the BW wheels and ways are well built and make a good setup.

Regards,
Jack C.