Re: Terminology Questions

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Kev Pearce \(kevp.com\)"
<lists@k...> wrote:

> Hi all,
>
> A couple of quick questions if I may...
>
> Ball screws, lead screws or simple threaded rod (albeit stainless),

whats the main differences and which should I really be looking at for
a home build?

>
> I'm keen on replacing linear bearings with the rollerskate bearings

idea unless the proper bearings do more for me?

>
> All comments welcome...
>
>
> Cheers
>
> Kev/.
>

Probably some reading in the archives will shed the most light on the
topics you mentioned.

One question is of screws.

Threaded rod can pull so much before the friction starts to climb
excessivly. for light duty and non-contact machines it works fine.

ACME is the next best, but if it seems low cost, it is because it is
not 'leadscrew' ACME comes in qualities. some is archetechual grade.
like the stuff on import vices and C-clamps. not high finish and no
need for it.

Leadscrew is much higher quality and is finished with a smooth finish.
but the friction is low(er) across the board.

Ballscrews are really rotating ball bearing in an expanded track.
VERY low resistance.

For a PCB machine or foalm cutter, anything will work. so, it really
is based on the machine design.

Next is thread.
1/4-20 requires 20 rotations to move one inch.
1/2-5 ACME requires only 5 rotations
1/2-0.5 Basslscrew moves 2 rotations per inch.

When you look at motors, you get more delivered HP from the same motor
as you increease the number of revolutions per inch. Smaller motors
are favored for very high pitch counts.

If you are into your first machine considder all-thread, but leave
room for ballscrews and their larger nuts.

Cheaper to get started, and an open up-grade path.

That should offer a little bit of a starting point.

Dave