Re: leadscrew, acme screw, threaded rod, ballscrew

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> I see that acme screw is a kind of square thread. But I see also

ball

> screw using square threads. Are these acme screw? So is the
> difference between drives using acme screw and ballscrew existing
> only in the type of drive nuts they use - with the ballscrew having
> recirculating balls?
>
> Al

Acme threads are square on top with a slight angle on the thread
profile and the bottom of the thread is the inverse of the top (flat
with sloping sides). A ballscrew uses a acme type form with one
major exception. The bottom of the thread is radiused to match the
diameter of the balls in the nut. The threads act as a
bearing "race". THe efficiency of a ballscrew approachs 90% compared
to as low as 30% on other types. You can hold a ballscrew vertical,
gice the nut a slight spin and it will continue on its own to the
bottom. You can actually push on the stationary screw and force the
nut to turn (power will transmit from the load to the source). None
of the other types will do that. The difference is like a sleave
bearing VS ball bearings.

The term "leadscrew" is a universal name given any screw type
mechanism that drives a linear motion. It's sort of
like "driveshaft" ; it does not describe what kind of mechanism it
really is just, what function it performs.