How do you turn-down the ends on a ball-screw?

[samualt]

How do you turn-down the ends on a ball-screw? There are some ball-screws I'd love to buy but the price doesn't include having the ends machined-down so I could use a bearing block. How are you supposed to turn them down?

[Bubba]

samualt,
In my case, because my atlas/craftsman lathe is not ridgid enough to cut the hardened screw directly with even a carbide insert, I ground it!
This was done by making a "tool post" grinder by making an adapter to hold my air powered die grinder. I goverened the speed by putting a quarter turn valve in the line. For the wheel, I found the cheap ones that at the hardware store used to sharpen mower blades etc and designed to be chucked up in a drill motor (3600 rpm max), about $2 each. It worked quite well and by grinding, I was able to cut beneath the hard stuff and then finish machine normally. Took about an hour per end as I went slow.

Bubba

[Torsten]

You could aneal the ends before machining.
Wrap the Ballscrew in wet rags to prevent the main running surface to heat up.
Leave about 4-6 inch at the end to stick out.
Heat this end with a torch evenly until it glows a light orange color.
Allow this end to cool of slowly by air do not accelerate the cooling.
Now you should be ready to machine this using carbide tooling.
Good Luck

[the4thseal]

how do you chuck up the screw so that you do not damage it? I assume concentricity is important.
TC

[Swede]

Hopefully this will be just what you're looking for...

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

Good luck!

[ViperTX]

Well let's open up this "can of worms" again. I tried Swede's method....delrin went on about 1" and it's only 3/4" long.....and I had to heat the delrin to get it that far.

So, any other methods to hold the ballscrew in the chuck?

Roland of Cardinal Engineering machines a "stub arbor" and attached it to the ballscrew without machining the ballscrew....a friction fit with setscrew backup. Anyone attend this past summer's CNC gathering and get the latest from Roland?

[carlnpa]

I used a strip of a cut up aluminum soda can on a three jaw self centering chuck. Strip was just short of fullwrap on screw. This didn't mar the screw for me YMMV.

[ViperTX]

calnpa....yep, thought of using that....centering the ballscrew is the problem....

Oops...I think I remember how an old veteran recommended on Home Shop Machinist....use a piece of bandsaw blade where the teeth have been ground down....attach the blade to the tool post holder and rest the blade on top of the ballscrew...put a little tension on the blade....test indicator rests on top of the blade....giving you a surface that will vary with the ballscrew.

A small piece of spring steel or even a old feeler gage would work in place of the bandsaw blade.

[Joey]

i`d rough bore a mandrel (pot) with internal undercut area to suit 1 or 2 side lock screws.
whip it out and drill and tap the screw holes, fit brass screws.
Back to the lathe and finish the bore to snug slide fit with ball screw OD.
when tightening up i`d locate the screw into the thread groove.
that should cope with any torque while machining the ball end.

how much material do you need to remove ? is that extra material left
on by the manufacturer to use to final grind the screw ?
If not try and buy the screws from them prior to heat treatment, finish the ball
and return to them to be hardened with the next batch.

Or `side servo` spark erode the ball end and finish polish on the lathe.

[mxtras]

Why not bore a set of soft jaws (or aluminum soft jaws) and clamp and cut lightly? Or indicate it in and cut an accurate center, then turn between centers with a drive dog?

Scott

[ozzie34231]

Assuming you can chuck the screw accurately, I drill the soft center of the screw and then silver solder a premade plug into the hole, without removing the screw from the lathe. After it cools I machine the plug to the configuration I need. I've done it a dozen times, works great.

(To chuck the screw, I use an odd size 5c collet I happen to have, that fits snugly, and additionally a home made chuck on the back of the lathe spindle to keep the screw from whipping.)

Jerry

[LeeWay]

Two sets of jaws came with my mini lathe. Smooth and notched. I have a 4 jaw as well, but the tree jaw smooth worked best. I did use a live center on the tail stock. I also supported the loose end outside the lathe with a 2x6 with a little large hole drilled. I mounted it to a bench close by.
I went through a carbide cutter on each ball screw getting past the hard shell. It was all the mini lathe could do to get it done. Very slow going and it must be tuned up as well. I used steel feeler gauges between the smooth jaws and the screws.

I recommend the tool post grinder though. Even one made from a Dremel or Rotozip would do if it's VS. You will be far less rough on a small lathe and go through fewer cutters. Probably go through some grinding wheels but should produce better results.