Ballscrews for a micro mill

[itsme]

Hi there,

I'm looking at buying ballscrews for my Sieg X1. I've had a quick measure under the table and it seems like I'll be able to fit a 10mm screw in there (I have approximately 24mm for the nut to fit in).

I've had a look at some SKF ballscrews that are 10mm in diameter and have a 2 or 3mm pitch. The nut should fit under my table. The screws are not preloaded and they have an accuracy of 0.07mm/300mm.

The first question I have is whether these ballscrews are likely to be 'strong' enough for my machine?

I am also not familiar with preloaded ballscrews (or any ballscrews for that matter). What are the advantages of preloaded screws over non-preloaded screws? The accuracy of these screws should be fine for my application, and seeing that the mill only has travels of roughly 150mm, it is even better.

I already have angular contact ball bearings on my machine which is using the standard leadscrews at the moment.

Regards
Warren

[itsme]

Hi there,

Well, I just bought a pair of SKF ballscrews for my mill on ebay. They are 10x3mm and aren't preloaded. They have an accuracy of 0.07mm/300mm.

Any thoughts on this? Good? Bad?

Regards
Warren

[wisp]

Hi Warren, that was me you purchased the ballscrews from on ebay. thanks! The wife is supposed to drop them off at the local UPS shipping office today, so they should arrive sometime next week.

I think you will have no problems with screw being strong enough for an X1 micro mill. They are rated at over 500lb dynamic load. Thats enough to stall the motor or break any cutter you could possibly load. They should fit under the table with little problem, I also have an X1. <I am working on some motor mounts to fit the X1, just need to finish cutting the X&Z axis'.> Here are some pics of the Y axis mount.

One of the ballscrews you bought still has the ballnut in its own bag with a brass retainer tube to keep the balls from falling out, as it has never been mounted. Be carefull when you thread the ballnut onto the screw, you dont want to loose any balls. Just hold the brass tube firmly against the end of the screw, then thread the ballnut on. Its not too difficult, ive done a ton and not lost any balls.

"Preloaded ballscrew" only means that the nut has at least two seperate rows of balls in it, or that are two ballnuts, and these two rows press against each other making the ballnut fit very tight, eliminating backlash.


Let me know how your project turn out.

cheers