Different ACME

[kolias]

I’m making plans for a new CNC router and I wonder if I can have different size ACME screws for the axes like use 5/8”-10 for the Y axis and 1/2"-10 for the X & Z.

I think by going with 5/8”-10 on the Y axis it will decrease the whiplash on this long (about 36”) axis.

[Hood]

Yes, it would make no difference at all to Mach. Even if you had a different TPI then it wouldnt matter as each axis is set up via Steps per unit.
 The only way it would matter is if you had a slaved axis, the master and slave would need to be the same steps per unit, having said that it is possible to still have different pitch on the screws if you gear the motors accordingly so that the steps per unit work out the same.
Hood

[RICH]

I think by going with 5/8”-10 on the Y axis it will decrease the whiplash on this long (about 36”) axis

Suggest you have a look at some of the ball screw manufacture info reguarding length and diameter of a screw
relative to it's mounting and speed. How straight the screw is over it's length also will have an influence.

RICH
   

[kolias]

Thank you Hood, nice to know

Thank you Rich but ball screws are way out of my budget. This is only a hobby CNC

My present CNC has a 36” long Y axis with 1/2”-10 precision ACME screw and I had a lot of whiplash until I installed a home made anti vibration damper and after that it was fine. Still I had to be careful because at higher travel speeds the weeplash will come back.

Now I think if I go with 5/8” precision screw on the Y along with my damper it will be just fine.

I get the ACME screws from a machine shop in Florida and they are made to order, very high quality and good service

[RICH]

Now I think

Missed the point of my reply. You will find info on those sites on how to evaluate the affect of different diameter screws
when used at different speeds and supported differently. There are charts or you can do the calculations and that provides you
with an engineered approach with answers rather than subjective recomendations.

RICH

[ger21]

Get 2, 4, or 5 start acme, so that it spins slower at the same speeds. My Y axis has 1/2-8 2 start acme, and about 32" of travel, and has no whip at all at 200ipm.
If you need to go faster, go with 1/2-8 4 start or 1/2-10 5 start. Both are 2 turns/inch.

[kolias]

Sorry Rich I misunderstood, it’s true that they have very good info because I went there before when I was building my 1st CNC

Gerry you are way ahead of me LOL, that was my next question and got the answer even before I asked. I guess I will go with 1/2-10 5 start. Good for my education, thanks

[kolias]

The 1/2"-10 Five Star Acme comes in 1018 Carbon Steel at $9.58 / foot or Heat treated 4140 Alloy Steel at $14.12 / foot.

Obviously the 4140 must be of better quality but is it necessary for a CNC?

What would you recommend?