Re: [CAD_CAM_EDM_DRO] Ball screw lead

On Monday 12 January 2004 14:30, jamesmcguiness2001 wrote:

> What am I missing? I realize the advantage of ball screws is
> the "zero" back lash advantage, (much better than the lead screw in
> my cross slide), however how do you get the incremental movement.
>
> On my lathe the cross slide has a .002 per increment and a 40
> increment dial. This means that the distance in one revolution
> is .080.

that a weird thing, sure its not a metric lathe (2mm per rev) I think you get
.040 of a yard or whatever it is to 1mm

> Most of the ball screws I have found THK for example
> have .500 to .200 lead per revolution. Seems like there is a loss
> in incremental movement.

Ballscrews are designed to be moved by stepper or servo motors, through a
gear system that alows them to achieve the precision they need. Very low
friction, low backlash and extremely long wear cycles. Coarser pitch means
less revs to get the job doen, and the fine control of a servo system still
allows them to achieve the precision they need.

Leadscrews are designed for hand operation, moderate friction, medium wear
cycles.

Because of the way they work, ballscrews tend to have coarser leads than
leadscrews.

If you tried to use a ballscrew in a lathe cross-slide, you would find that
a) the lead was a bit coarse (as you have noticed) and b) you would have to
provide some additional friction to the shaft to prevent it being pushed
whilst in use and rotating.

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