How to cut and turn ball screws HELP

[Spitfire]

Hi
I am trying to turn down a 16MM ball screw to fit bearings and stepper motor ,
and i am haveing a hell of a job with finding a tool which will cut them.
Can any one give me any info on what type of tool and speed to run at.
the ball screws are 16mm 5m pitch
any help would be appreciated the lath is a 920.
Thanks BIll

[kdoney]

I've found abrasives are the answer. I cut with an abrasive wheel on a chop saw and grind the ends with a tool post grinder on my lathe. Don't worry about the length the lathe only holds the work, the grinder does the cutting.

[ShayArnett]

Yep, because they are soooo hard, I have only ever seen people using toolpost grinders to turn them. Search around, should be pretty easy to find some plans for a dremel toolpost grinder.

[bill south]

Bill, careful handling the screws in the lathe. Make sure the non-work end is supported so that you don't warp the screw. It is most likely case hardened, so you only have to grind off the outer few thousanths to get to softer metal. I have used a hand held grinder (didn't have a tool post grinder) to knock off the outer skin then cut it with a carbide tool. The last nook screw I cut was with an abrasive chop saw (cut off) to the right length and then turned the end with my 9" lathe and a new carbide insert. Spitting Sparking all the time until I cut throuth the case hardening. I then changed to a new edge on the tool and made my finish cuts to the correct size.
Hey forum experts, this worked for me but if I'm giving bad advice, jump in here. Don't let me screw up by giving bad advice. But again, worked for me!
billyjack

[Spitfire]

Hi Guys
Many thanks for the information, i have not got a toolpost grinder but i do have
a 4" angle grinder, so i will give it a go.I should be able to take a fair bit of of the case hardening before turning it.Any one got any sites for a tool post grinder plan.
again thanks
Bill

[Al_The_Man]

There is an article by one of the members of the Forum on his site http://www.5bears.com/cnc16.htm
Al.

[phantomcow2]

I have the same screws, 16mm with a 5mm pitch.
8 of them to be turned....

It is a horrible job, and I have only a 7x12. Do not even bother with HSS. THese things are approaching the hardness of the HSS tool bits. You have two practical options:
1. Anneal the ends by heating it until it's cherry red and letting it cool. THis makes it machining friendly.
2. Use carbide tooling

[ViperTX]

Geesch....it's not a horrible job...thinking about it....well now that's horrible.

As Phantomcow mentioned.....once you have cut the ballscew with an abrasive cutter then heat treat the end.....wrap a wet cloth around the area that you don't want to heat treat......heat it up to a cherry red color ....rotate the ballscrew as you heat it....

Now, I tried the 5 bear method.....and while it may work it's more work......so, my method which I developed after trying the 5 bear method....

wrap a piece of aluminum (like from a beer can or soda can) around the ballscrew where the jaws of your 4 jaw chuck will press against.....then use a flexible piece of metal (like a thin putty knife blade) which is held in the tool post.....it will rest on top of the ballscrew.......your indicator will ride on the 'putty knife blade surface' close to the middle of the ballscrew.....forgot to tell you support the end of the ballscrew that is sticking out of your lathe spindle with a board that has a large hole drilled in it.....wrap a piece of cloth around the ballscrew and slip the board over the ballscrew....I use a heavy vise to hold the board.....what you are trying to eliminate is the ballscrew whipping.....

So, as you slowly rotate the 4 jaw chuck....mark the jaws.....you start centering the ballscrew......

Using carbide tooling face off the end of the ballscrew...then center drill it.....and use carbide cooling to cut the bearing journal.....now you can follow the rest of the 5 Bears process.....

[Spitfire]

Hi Viper
Many thanks to you ,and all the other guys for the infomation.Regarding the carbide
tooling do you guys use insert type or the brazed on type for this type of work or does it not matter also what spindle speed do you run at.
Thanks all Bill

[phantomcow2]

inserts, brazed tips, it does not matter.
Inserts, having a round radius, requires a hefty lathe. Even the 13x48 engine lathe at my school, there was noticable chatter with inserts.
So if it was me, I would use brazed. As with all tough steels, you want low RPM and feed. You can go higher in RPM and feed, but again, need the lathe to handle it.