Ballscrew or leave alone?

[i2i]

ballscrews all the way...worth 20 times the cost of the leadscrews.

[Jonathan]

Leadscrews are OK to get started, as it's generally very easy to just add motors and use the original screws. You can probably then change to ballscrews without wasting much if any money on parts. However, you'll soon find that backlash, low efficiency and wear (to name but a few) make the overall machine much less useful than it could be.

[Ross77]

ballscrews all the way...worth 20 times the cost of the leadscrews.

What he said..

You can easily get rid of backlash in lead screws by tensioning (or compressing) two nuts together but the resultant friction is often more of a problem than the backlash. My little mill has has this type of anti-backlash and I can get pretty much zero backlash but the friction is so high it is difficult to turn the hand wheel and impossible to get smooth motion. as already pointed out this will also result in the screw wearing out quickly.

The halfway house is to use brass nuts and a hydraulic tensioning system to self adjust for the wear and then replace the nuts as when they totally wear out. but by the time you set that up it is probably easier and cheaper to get a ball screw.

Don't be tempted to use delrin, been there done that and it has no place in milling machine. I've learnt from my mistakes and I'm getting ball screws for the next one.

[John S]

Done a few WM16's and one thing to bear in mind is that some convert easily and some don't.
The stumbling block is the bed in the middle, the casting when being cast, sags and make the gap tighter in the middle.
No problem with the top, that's machined so no sag. From the ones I have done it's 50/50 if a ballnut clears.

So worst scenerio is to get someone with a big mill to take a lick out or angle grind a clearance grrove.

WM14 are usually OK, I haven't come across a bad one but WM 18's 'always' need machining

[manofgresley]

Many Thanks, Any thoughts on the couplings?

Ray

[John S]

Oldhams, they are the only non backlash coupling that works CORRECTLY in two planes.
All the others are fück ups.

[manofgresley]

Hi John

I agree, i have used Oldham couplings for many years, i just thought things may have moved on a little, they seem so expensive these days.

Regards
Ray