I am looking into building a custom CNC mill from scratch, and I need to figure out what ballscrew I want...I have heard that ground ballscrews are best.

However, I can't decide which brand, length, travel, etc.- Can someone set me straight?

Thanks,
Burn

Length and travel are all packaging issue on the machine you're working on.

HIWIN is a noted supplier of ground screws. They have bolt-in ones for Bridgeports of varying lengths for the various axes that are affordable and surely adaptable.

Assuming I go with the Hiwin screws, what model do you reccomend for a build like this? Thanks :D

It is impossible to make a recommendation - you're "specs" are WAY too generic.

Check out what's available, comparison shop, get a price quote, if it meets your needs and/or budget pull the trigger and buy it.

For starters, what diameter ball screw do you suggest? They will be driven by servoes from IMService, which have 1/4" Diameter shafts.

For hobby type machines, or for more precision for that matter, I see no reason to use ground ballscrews when rolled ballscrews will do the job.

When you make your production setup, you can offset the cutting tool to maintain your dimensions, but the encoder must be first rate in order for the screw to repeat.

I second hte Hiwin recommendation, I have 3 of their ground ballscrews that I will be using for my X3 CNC. Each one was machined perfectly, allowing about .0002" for a press fit of the duplex bearings inner races. Also, they all came with inspection reports.

If I had to pay though, I would just use rolled ballscrews. Member adobe machine noted .0008" of error over 28" using ROckford 5/8-.2 rolled. I think this is more than adequate for HObby use. Unless that is, you plan to hold a few tenths over 2ft+ lengths.

"CNC from scratch" - I assume this means a router. You don't need ground ballscrews. A high precision rolled or even avg precision rolled screw will work just fine, as will a single nut.

3/4 inch diameter for lengths up to 6 feet will remain pretty accurate, that is, not flex too much. This applies to any kind of ballscrew. They're all steel anyway. Of course if you go bigger, it'll be less likely to flex.

I'm a bit concerned though that you're asking about what LENGTH ballscrew to buy. Does this mean that if we tell you 5 feet, you're going to go out and buy that exact length? The length of your ballscrew should be roughly the length of your linear rails, which will be roughly a foot longer the travel of that particular axis, X or Y. You haven't even told us exactly what you're making yet.

Buying materials before you design a machine is a great way to waste tons of money. Especially if you buy ground ballscrews.

What metalworking experience do you have, and what machines do you own and plan to use to construct the frame of the router?

I'm looking to replace the ball bearings in thk sr15w slides. can some one tell me the standard size ball or where I can find the info for these units. I hoping to have the replacement balls on hand before I shut down to do this.
thanks
bill

Don't mean to change the thread.............are there different grades or hardness of acme thread......I read a post a while back when a guy was going to turn the ends of the acme but said to grind the threads down a bit to get through the hardened part . I just turned my 3/4 x 6 I purchaced
at ENCO........it didn't appear to be hardened at all. Was very easy!:wave: