Z-axis lead screw support bearing type?

[techvette]

I'm redesigning my machine. I'm not very happy with the Z lead screw system, which is using flange bearings like this one:



to support the lead screw. This configuration means that the weight of the Z is supported by the motor shaft coupler, a flange bearing at the top, and one at the bottom. Basically, three set screws are holding most of the weight.

I'm rebuilding the carriage out of 1/2" aluminum bar. I'd love to have a bearing that would support the bottom of the lead screw, taking the load off of the other bearings and the motor. But, I can't figure out what that kind of bearing is called, which makes it difficult to locate.

Help?




This one is blurry, but the flange bearing is visible-ish in the middle. The screw wasn't cut to length in this one:



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[ger21]

Here's how I did mine, with skate bearings.

http://www.cnczone.com/forums/cnc-wood-router-project-log/1356-another-first-router-post125415.html#post125415

[techvette]

Okay, I've gone through about 15 pages of that thread, and I can't find any specific mention of the bottom support of the Z screw.

I'm sure I'm just missing it?

[ger21]

That link takes you to the specific post that shows what I did, post #83.

[techvette]

That link takes you to the specific post that shows what I did, post #83.

Hmm... for some reason, the link sent me to page 7, message 181. Shrug. I went and found #83 at

http://www.cnczone.com/forums/cnc-wo...tml#post125415

... which is the same link you posted. If I open a new browser tab and paste that link, it still takes me to #181. Who knows.

Still, I found the message you were talking about. So, if I understand correctly, you've reduced the diameter of the screw at the end and used a bearing with an ID that fits the smaller end. This lets the larger-diameter quasi-flange on the screw rest on the bearing so that it can spin, and the bearing takes the weight rather than the set screw.

Does that sound correct?

[ger21]

Yes, I have a bearing on each side of the bottom plate, and the locknut on the bottom holds everything tight to the plate, so the two bottom bearings carry all of the weight. At the top, I just have a lovejoy coupling, and no bearings at all.

I've since changed the way that I grind down the ends. I still use the same jig, but chuck the screw in an electric drill, so it spins like it's in a lathe. I use an angle grinder to quickly remove most of the material, and use a file to get it cleaned up and to final size.

[techvette]

That sounds perfect. And, I can do it with parts and tools I have on hand.

Thanks for your help.

[Biggs427]

Another solution might be two thrust bearing. On my old CNC it worked pretty well and didn't had any play.