Ballscrews end bearings

How about this: "McMaster, unlike sources of cheap tools and supplies, might have this item"?

but yeah, they're not cheap. When you can't find it anywhere else, though, they're cheap enough.

What are you trying to accomplish with the retrofit? Do you understand that the amount of backlash in a ball screw does not necessarily correlate with the accuracy of the screw?

Ned Simmons

If you're thinking rolled ball screws, forget it, you won't eliminate backlash with them.

Indeed, achieving sub-0.001 backlash would be difficult no matter what you use. Count up the number of bearings involved, and the flex in the table and supports.

He didn't say whether he intended to use handwheels or motors. It's been pointed out before that ballscrews and handwheels are incompatible because there's not enough friction to hold position without locking everything down.

Those bearings have to be angular contact thrust bearings for best, or any high end thrust bearing. And I replace ballscrews in commercial applications when they get as much as 1 thou backlash.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

According to Ned Simmons :

And that use of a ballscrew with a manual machine is asking for trouble. If you intend to drive this with servo motors or stepper motors, ballscrews can make sense. If you intend to continue to use it as a manual machine, beware that the cutting forces can drive a ballscrew as long as you don't have your hand on the crank (and with a mill, there are three controls to need hands, or four, if it is a knee mill). Let go of an X or Y crank to crank up the knee or down the quill, and when it starts cutting it can self-feed (doing climb milling) until it reaches the end of its travel.

The bigger the machine, the more exciting such an occurrence can be. :-)

I don't see the original posting, so I don't know whether you intend to use this for a CNC conversion or for manual milling.

Normally, *all* manual mills (and lathes) have backlash in the leadscrew/nut interfaces, and normal practice is to always approach a position from the same direction to minimize the effect of backlash.

Enjoy, DoN.

Can an average Joe buy small quantities from them? I didn't see any pricing, ordering, or distributer links on the pages.

Four weeks? What is this the 19th century?

I understand very little about any of this. I'm looking for accuracy and repeatability for benchtop-sized CNC. Dumping truckloads of money into it is an option, but not my first choice.

Yes. Just click the "getta quote" button on their site. (Response time was 3 business days. It was only coincidence that Tom mentioned Nook.) Having gotten the quote, I'm still trying to remove it from the orifice in which it got jammed: [[

Thank you for your interest in Nook Industries Ball Screw Assemblies. Per your request, please find the following price and delivery.

Qty 1, 0631-0200 SGT RH/2K/2K/28.00/SGN10083/FS, $1405.20. Please allow 4 weeks to ship.

]]

I could buy a lot of beer (or something else) for that money, and the reason I write. This is a 3/4" screw, 28" long, ground, hardened, with a double nut and doubled ABEC-7 angular contact bearings in holders each end (fixed each end).

For CNC milling, then, what's the strategy for final finish cuts? Single direction cuts would double the operation time, at least for aluminum. Is backlash with rolled screws consistent enough to compensate in software?

That part didn't bother me so much. I pretty much stopped reading slightly past the dollar sign.

That is for sure. They get you coming and going!

That does seem like a lot of mula, but it also sounds like the top of the line.

First off, is the mill worth spending the money to achieve the accuracy desired? Will replacing the ballscrew and bearings solve your accuracy problems?

Do you have excessive wear in the ways and gibs surfaces of the slide/axis you are trying to correct OR in another slide/axis as well? Is the accuracy problem in the compound slide/axis or somewhere else? For instance, spindle bearings, quill, vertical slide/axis ways and gibs. Finally, class your bearings with the class of your ballscrew. Example-Class 7 bearings (ABEC 7) bearings are of super precision grade, ground to .00005 tolorances and capable of holding the same tolorances. Put these bearings on a rolled ballscrew and you will achive nothing more than the accuacy of the screw (probably no better than .001) and a lighter wallet. Kinda like putting a Porche engine in a Volkswagon, gonna run like hell in the straights but still gonna handle like a Volkswagon in the twisties. Nook does make some good precision ballscrews and probably will exceed what your machine is capable of giving you even with Class 3 bearings (ABEC 3).

It runs OK. Holds .002 on smallish parts without much thought or effort; .001 and under is a bit more problematic. Not bad for "junk", but wondering if that's enough to get a fine or even semi-fine finish after converting for CNC. My best think-gem to date, I think, was to just bead blast if machining marks proves to be a problem. Certainly takes care of the cost problem... Also, considered briefly building one up from scratch on linear motion rails, but found those are astronomical, too. So here I are... wondering if $200 an axis in rolled ballscrews will solve a problem I'm not even sure I'll have. And once you start down that slope, ...........

There'e my disconnect. The Machinery Handbook lists only ABEC-1 and -7 for angular contact bearings. Parts suppliers similarly offer $20 a pair bearings, or $400+/pair. Led me to believe there was nothing in between. So, agreed; that would have been the better question to ask initially. :) Still, the only middle ground I'm finding are eBay and SE asia salvagers. Where else am I missing?