Ball Screw Source for Conversion

[RTP_Burnsville]

Hi,

I have been looking for a ball screw source from which to purchase new ball screws for my first X2 mill conversion. Ideally I would like to purchase screws which have machined ends (type II) in either 1/2 inch or 5/8 inch diameter, .200 inch pitch. I have collected a few catalogs from places like Roton, Mac-Master Carr and a couple others but it appears that none of them have standard machined ends available. Where have you folks purchased ball screws from? Are rolled screws from one manufacture better or worst than those from another?

I don't want to just purchase a conversion kit being that would take the fun out of the whole project. Besides I have already collected everything I need except for the ballscrew assembly.

Recently I picked up a 7x10 mini-lathe but am not sure if it would be ridgid enough to work with hardened steel. If one were to aneal the shaft end would the 7x10 have a chance at success? Also I could build a grinder attachment but that would be a fair amount of extra work. I am guessing there is only one shot at getting it right or else go broke learning... Thanks for any assistance.

Robert

[NC Cams]

Check out HIWIN and Rockford.

Have HIWIN rolled thread screws on my Bridgeport and they are quite adequate for the work we do including precision CNC milling of some cam masters for cam grinding. with proper machine tune-up, we can hold to within 0.0001 or so of a CNC target data.

HIWIN has a number of bolt ins for popular machine tool systems. They have a website.

re: SCREW RESIZING/MODS: We do custom grinding and have done shaft resizing (sorry, no rethreading) on acme lead screws (hard or soft). We do tool and hard steel OD grinding all the time. We could to a ball screw end w/o annealing it depending on length and if it has centers.

Contact me directly via e-mail for pricing as this type of work is done on a time and material basis as time permits. Be sure to provide a dimensioned and toleranced sketch showing what you want us to do with the RFQ.

[RTP_Burnsville]

Thanks for the response. I'll check out your suggestions and if I need to have the ballscrews turned I'll drop you a note.

Robert

[ger21]

http://www.homeshopcnc.com/page2.html

[NC Cams]

I have moderately preloaded HIWIN's with a rolled thread on my mill and they are as smooth as glass (see FAQ's on posted link).

And, like every thing else, there are levels of accuracy even in rolled ball screws. From the price comparisons I"ve dont, I'm pretty certain that a set of rolled thread HIWIN's will cost multiples of those in the homeshopcnc link.

Surely, the level of quality and accuracy will ultimately affect the price of the screw. Ultimately, it all depends what you want to do and how accurate you want to be. Speed and accuracy costs money - how fast and accurate do you want to be/get???

[wildcat]

Is it reasonable to perform end machining on a rolled Rockford ballscrew on a lathe or is some sort of precision grinder necessary?

[Willbird]

In a perfect world I would rough turn them in a lathe and chase the threads for the retainer nut to preload the bearings, then OD grind the bearing seat to size....but in a pinch you could do it all in a good lathe if you were carefull.

[ger21]

Originally Posted by wildcat Is it reasonable to perform end machining on a rolled Rockford ballscrew on a lathe or is some sort of precision grinder necessary?

http://www.5bears.com/cnc16.htm

[Zumba]

Willbird's perfect world is rather attainable thanks to toolpost grinders for the lathe. I absolutely hate lathes and mills made in China, but certain attachments like the $99 toolpost grinder from www.littlemachineshop.com actually work quite well... at least for ballscrews where you're only grinding about 1-2" in length. I'm sure it would suck for grinding a very long shaft.

[Willbird]

I have a toolpost grinder Zumba, but the base level precision would really not be all that much better than just turning the dang thing IMHO, the factors in accuracy would be much the same either way. Plus you have to swaddle the lathe all up in flypaper first to not get grit into it's bits :-). Tool post grinders in my experience shine only on things too damn hard to turn :-).

The advantage the OD grinder has is that the part rotates on truly dead centers, so that no bearings are involved in the roundness of the part. I CAN think of a way to do that on a normal lathe, but it would not be simple :-).

I have been thinking about asking Mr. cams about what happens to AC bearings when they are preloaded anyway, so here goes, do the races expand (outer) and contract(inner) when the bearing is preloaded ??

Bill

[MonoNeuron]

Hi Rtp, I off hand ground 1 of my screws first on a bench grinder with a lot of quenching inbetween and then machined the ends in the lathe at a very low speed (about 90 rpm) and they turned out great. Just make sure you have a sharp tool without too much rake angle on it (back slope).
I only turned down the 5/8 screw for 1" of length and 7/16 dia then shrunk fit the bearing support shaft over the ballscrew screw spiggot. It hasn't moved.
The Neuron.