RE: [CAD_CAM_EDM_DRO] Re: Sherline Z-axis ballscrew feed.

> -----Original Message-----
> Tim:
> Wouldn't two nuts on the leadscrew result in too much drag for the
> stepper motor for the Z-axis? I thought that one of the attractions
> of using ballscrews was the low friction and less wear than
> normal thread-type leadscrews? I think a ballscrew for the
> z-axis is a
> fine idea. Now, if someone can just do it and work the bugs out,
> we can just retrofit our mills. ; ) -Jim

It is not a problem with drag if adjust properly on the X and Y, so why
do you thing it would be a problem on Z? Of course if you are using a
marginal motor already it will be.

My point was just that ballscrews are not the only solution. I know what
Dan is machining and he has no need for rapid Z movements so a split nut
would be a perfect solution for him. You are correct about some of the
great qualities about ball screws, but you do not mention any of the
negatives. They are easily contaminated with swarf, precision versions
(better than a .003"/ft or so) are VERY expensive, they require more
room than most other systems, etc, etc. They are far from the only
precision solution and in much of the high precision lower speed and
force (which describes a Sherline quite well) positioning system you
will find non-ballscrew zero backlash systems. I had a super high end XY
table that was rated for positioning in the .0001 or less range. Guess
what, not a ball screw in it. It was multi turn acme with loaded plastic
nuts. This is on a table that sells for well over $1000 for a 6" x 6"
travel.

So, if you want to over engineer, throw a lot of money at it, and not
have a working solution for a couple of months put a ballscrew on your
Sherline. But, if you want to fix the problem now a slotted or split nut
would do the job and have your lash fixed in an hour or so. Now if the
machine we are talking about is a full sized mill the answer will be
quite different. You don't need a sledge hammer to crack a nut and you
don't need a ballscrew on a Sherline.

Tim
[Denver, CO]
Beat the Sherline Oct 1 price increase. Order Now!
New Sherline Prices at http://www.ktmarketing.com/SherlineIncrease.htm

Sherline & Taig products at Deep Discount
Mach1 & DeskCNC with credit card ordering
www.KTMarketing.com/Sherline
e-mail me at Timg @ KTMarketing.com for items not yet listed