Best way to machine ball screws?

[Colin Barron]

Would it help to stick the pin in the freezer and the end of the screw in boiling oil.

[John S]

You have been watching too many medieval siege films.

.

[Colin Barron]

This is a method to fit main bearings into an aluminium crankcase, instead of being a tight fit with the risk of damage using this method the bearing would just drop. It is also used on high speed drills and collets.

[John S]

Sorry I missed the smiley. :lol: :lol:
You are not American are you ? :whistling: :whistling:

[gavztheouch]

I think I have read about every thread, tutorial and watched every youtube video on ball screw end machining there is. Now im about to start machining some screws for my laser cutter.

I was about to start by grinding of the hard casing with a bench grinder, but I reckon my 15mm diameter rolled screws will still be hard at the required 12mm dia for the bearings.

I only have a Myford MLR so carbide tips are out, so I reckon the steel rod glued into the ball screw sound like the best idea.

Has anyone got any suggestions as to the best type/number of loctite to use.

[JAZZCNC]

I was about to start by grinding of the hard casing with a bench grinder, but I reckon my 15mm diameter rolled screws will still be hard at the required 12mm dia for the bearings.

Not necceserialy If chinese origin then think you'll find there only 3-4mm of hardening.?
I've machined a few, I use indexed tipped tooling and buy tips from cutwell tools designed for cutting hard materials. They easily deal with hardening, my lathe is a bit more robust than the myford but it's only a boxford AUD so not exactly heavy duty.!!

Maybe some body's got a bit of an offcut that you could practice on.? . . . Don't think I have but will have a dig about if you want to try.?

EDIT: Opp's sorry didn't read properly didn't see the 12mm dia,yes it will probably still be hard but the hard tips will still handle the hardening on chinese screws.!!

[John S]

Problem is here that the OD at 15mm will start to become the softer core at 12mm but the roots of the thread will still be hard so it's very hard to get an even finish at the 12 mm diameter.
For 15 down to 12 I'd grind them on a cylindrical grinder, only way to get a true surface.

can you redesign and go down to 10mm ?

[gavztheouch]

Thanks,

I think they are Chinese, they are branded Gten. Definitely not top quality whatever they are?

What sort of carbide holder and tips would you recommend? I am looking to try a carbide holder for my Myford so a nice general shaped holder would be ideal, but I am new to lathes and don't know what that would be?

Thanks for the ball screw offer, but I ordered some extra length on each ball screw to try it out.

The only problem would be I have a HSS threading tool and the 12 dia might still be too hard to thread with that.

[Jonathan]

Thanks,

I think they are Chinese, they are branded Gten. Definitely not top quality whatever they are?

I recently machined some Gten 15mm ballscrews ... they were a nightmare compared to the standard Chinese (RM1610, RM1204 etc) ones I've done. The metal was still very hard at 12mm, so no chance of getting anything like a good enough tolerance/finish to fit a bearing unless you have a cylindrical grinder as John S suggested. Instead I just annealed the ends of the screws using the wet rag technique to limit how much is annealed, then it was easy. I didn't want to go down the putting bar into the ends of the screws since these ballcsrews were going to be put in tension - not sure if they'd hold up to that?

This is what it turned out like:

[JAZZCNC]

What sort of carbide holder and tips would you recommend? I am looking to try a carbide holder for my Myford so a nice general shaped holder would be ideal, but I am new to lathes and don't know what that would be?

Will need the smaller holders which often have CCMT tips. The holder I use is SCLC with CCGT or CCMT tips and this the company I use. http://www.cutweltools.co.uk/home/la...g-tool-holders
They arn't the cheapist but they are quality, Can't remember the number of the tips I just told them what I wanted to do and they sent me the tips. They've worked a treat on hardened screws I've done thou I dont get more than 2 screws per tip (1 screw per tip turn) and it's slow away stuff. ( I use them on softer materials like ALu or delrin when the edge goes off on hardened stuff).

BUT . . . If your new to turning then I strongly urge you to practice on some scrap before you try machining ballscrews for real.!! . . . You don't often get a second chance.!!

Same goes with threading, if you haven't done much threading then get plenty of practice before attempting on ballscrews because like John S mentions the hardening hisn't always consistant so can easily have soft and hard spots which can make threading a real bitch, esp on a small machine that flexs.!! Again I use indexed tipped threading tool, to be honest I can't be arsed with HSS and grinding for standard stuff like threads or run the mill turning and only grind for special or awkward jobs.!! . . . Yes it's more expensive but not too much when you consider the time saving and repeatabilty of tipped tooling.!
Annealing works but again got to be done carefully and correct other wise can spread up the screw further than desired.!!

Practice and practice a bit more is my advice then go for it if you feel confident.!!