Turning hard materials

[Harry Hills]

Hey all,

I'm having difficulty turning the ends of my ball screws down. The material seems pretty hard and it seems to be a lot of hassle to get things to cut and then it turns out pretty sloppy and inaccurate with a terrible finish.

Am I best going with a toolpost grinder or is there some trick or other turning tool I could try?

Thank you.

[Jonathan]

Easiest way is just to anneal the end of the screw. Heat up the end and wrap a damp cloth round slightly further back to stop most of the heat conducting down the screw.

If you're careful you'll end up with maybe 10-20mm of the portion you're not machining no longer hard ... but if your ballnut doesn't go that far then it's nothing to worry about.

[dodgygeeza]

as Jonathan says annealing is not that hard to do. if the screw is not too long, you can put the screw in a bucket of water with the part you want to anneal sticking out of the water. also remember that after annealing you will most likely need to straighten the screw and you will be best to use a collet rather than a chuck.

[komatias]

For the visual type:


https://www.youtube.com/watch?v=dzIsR4Mg158

[Neale]

So, all you need is a convenient induction heating unit! I was a little surprised at the straightening that was done. Assuming that any distortion would occur in the annealed section or at the boundary between that and the "left hard" section, wouldn't any slight loss of straightness be taken care of in the machining? If you are using the untouched threads to hold the screw (decent collet, etc) then I would have centre-drilled, brought up my tailstock centre, and just turned to dimension, confident that the turned part was going to be concentric with the body of the screw. What have I missed?

- Brian

[Jonathan]

So, all you need is a convenient induction heating unit!

I've been resisting the temptation to buy one of these for a while:

http://www.ebay.co.uk/itm/1000W-ZVS-Low-Voltage-Induction-Heater-Flyback-Driver-Tesla-Voil-12-48V-20A-DIY-/311140987806?hash=item487172b39e:g:0x4AAOSwcu5URhO k

Perhaps I should stop resisting....

[Neale]

I've been resisting the temptation to buy one of these for a while:

http://www.ebay.co.uk/itm/1000W-ZVS-Low-Voltage-Induction-Heater-Flyback-Driver-Tesla-Voil-12-48V-20A-DIY-/311140987806?hash=item487172b39e:g:0x4AAOSwcu5URhO k

Perhaps I should stop resisting....

I gather that you've used the annealing method yourself - how did you heat the ballscrew, and do you think that there was any distortion? Was it machined out if so? I now have a lathe with a big enough spindle clearance for ballscrew machining, and trying to make sense out of the various sources of "advice" available via Google...

[Jonathan]

I gather that you've used the annealing method yourself - how did you heat the ballscrew, and do you think that there was any distortion? Was it machined out if so? I now have a lathe with a big enough spindle clearance for ballscrew machining, and trying to make sense out of the various sources of "advice" available via Google...

There are some pictures of one I did here - got a bit carried away with the heating, but I didn't notice any distortion - neither did I check carefully if I'm honest.

http://www.mycncuk.com/threads/4497-Micro-lathe-Zero-backlash%2A-conversion?p=30297#post30297

I used my Mum's cooker to heat it - it's a gas hob. Better off using something with a bit more power output though.

[Clive S]

I've been resisting the temptation to buy one of these for a while:

http://www.ebay.co.uk/itm/1000W-ZVS-Low-Voltage-Induction-Heater-Flyback-Driver-Tesla-Voil-12-48V-20A-DIY-/311140987806?hash=item487172b39e:g:0x4AAOSwcu5URhO k

Perhaps I should stop resisting....Not sure if that would do it from what I have been reading you need about 10Kw. Funnily enough I have been reading this today https://github.com/joshcam/ReactorForge/wiki/ReactorForge-Core but decided a good Mapi gas blow lamp would achieve the same result cheaper

[Neale]

I have a propane torch with range of burners from tiny to teenage dragon flame sizes. One should match "Mum's gas hob" plus a bit!

Thanks - always good to hear from someone who's actually done the job.

[Boyan Silyavski]

I've been resisting the temptation to buy one of these for a while:

http://www.ebay.co.uk/itm/1000W-ZVS-Low-Voltage-Induction-Heater-Flyback-Driver-Tesla-Voil-12-48V-20A-DIY-/311140987806?hash=item487172b39e:g:0x4AAOSwcu5URhO k

Perhaps I should stop resisting....


Jonathan,
what can this really heat ? Can it melt a coin or a gold ring? And would you translate the Changlish in the description to me? I have 15v 40A lab PSu that i used for anodizing. Will that work with it?

[Harry Hills]

Thanks for the replies people. Annealing the ends worked great. Thank you!

[dodgygeeza]

use map gas, it will be much quicker that using your mums stove to heat it up lol.
It needs to get cherry red to make any difference.
a tool post grinder will be a lot better and you can get much higher tolerances than normal turning, and a much better Finnish as well.
However, even if you use a tool post grinder you may still need to anneal the screw because where you turn the thread into the screw may still be in the hard or just on the edge where it goes soft, and this can be a bugger to put a thread for the locking nut if it is not totally soft.

[Harry Hills]

Yeah I used mapp and it was a breeze.

[AndrewMawson]

For future reference you can buy hard turning inserts made from CBN that will even turn HSS without annealing. Your lathe needs to be pretty rigid though.

[komatias]

Andrew Mawson as in Baron Mawson?

[AndrewMawson]

Andrew Mawson as in Baron Mawson?

I've told him before to stop imitating me :friendly_wink:

We have had email confusions in the past and have corresponded, but no, I'm not a 'social entrepreneur' whatever that is, but then nor did I get the Honour :beer: