machining ballscrews

[T0rnado69]

i hope this is in the correct area.

im looking at getting some ballscrews from ebay.
( link shows one i was looking at, but i need to make sure i get correct diameter and pitch ones for my lathe)

i want to replace the crap leadscrews on my lathe
as there is so much backlash

has anyone machined the ends them selfs before on a lathe.

are they easy to do. or are they hard as nails to machine.


cheers.

[JAZZCNC]

I've machined them before with indexed tip for hardened material without any trouble.!!. . BUT. . Those where chinese ballscrews if they are higher quality then you may find they need softening first.
That said if these ballscrews are coming from Chinese source then I suggest you let them machine them has they will do it cheaper than you can buy the tips. Provide them with a drawing and they will machine to your spec.!

Edit: Just noticed the Link. In this case I would ask them about machining or Send Chai an email along with drawings asking him for quote.

Edit: Lee Chai doesn't Mind is email being given out he gives it out him self on Ebay.!!

[EddyCurrent]

This is the machining diagram used, I asked Chai to extend the length of 'F' to 30mm so a pulley would fit better and he did that no problem.

http://www.mycncuk.com/forums/attach...-machining.png

Having said that I was able to easily file a flat on the turned down part for the pulley grub screw to tighten onto but I believe ball screws have a hardened outer shell that has to be broken through first.

[gavztheouch]

You can do it with hardend tips if your lathe is beefy enough.

Another method is to weld on some mild steel bar to the end of the screw and then use that as your machined end.

You can also grind off the hardend part then machine, or get it anealed.

Its also handy if you have a collet chuck to hold the screw in the lathe. That way you know it is well centered.

[corkcnc]

They are generally okay to machine, I used tips I got for stainless and they were fine. The only thing I found is that the diameter will vary a little if you are only taking a few mm off as the surface hardening is about 2mm deep. This means when you get to the diameter where the thread is just gone, you are still left with hard spots 2mm deep where the root of the thread was hardened. I'm not explaning this very well but think of two spirals of hard and soft material intertwined. If you can go 2mm below the root of the thread with your final OD then this effect is gone. If not it leads to the tip being pushed back more by the harder bands than the softer ones so don't be surprised if the same diameter checked across a couple of different point will vary by up to 10um or so.
I take shafts down to the final dimensions with 600 grade paper and this reduces the variance nicely.
Shafts will vary in terms of hardness and depth of hardness but there is nothing to fear either by taking on the task youself.
Rgds,
Noel.

[T0rnado69]

I've machined them before with indexed tip for hardened material without any trouble.!!
Send Chai an email along with drawings asking him for quote.
Lee Chai doesn't Mind is email being given out he gives it out him self on Ebay.!!

hi dean, i currently use brazed TCT tools i got from machinemart.
6 Point metal turning set and 38pce Carbide Tipped Lathe Tool Set

but have been planning on getting an indexed tool for a while, as they look much better and you just change the cutting tip.
as with the brazed TCT ones i have, you have to take them out and get them sharpened.

where can i find chai contact email..
cheers.

This is the machining diagram used.

thanks for the diagram eddycurrent.

You can do it with hardend tips if your lathe is beefy enough.
Its also handy if you have a collet chuck to hold the screw in the lathe.

the lathe is the clarke cl430
it doesnt have a collect chuck, just a 3 jaw and 4 jaw chuck.


thanks for the info corkcnc.

[EddyCurrent]

it doesnt have a collect chuck, just a 3 jaw and 4 jaw chuck.

That's a good point, I used a lathe to straighten some ball screws and a standard chuck does not grip it well.

The annealing process, http://www.roton.com/eng_bul_911.aspx

[T0rnado69]

i think what they charge to machine it for you is proberly worth paying,
with no collect chuck. more chance of it slipping and getting damaged ?
if you machine it and mess it up then wasted money on a ballscrew, only to have to buy another one.
so proberly better to get them to do it and you know its done correct and only have to buy it once.

[JAZZCNC]

No disrespect ment here but I don't think your setup enough to tackle ballscrews yet. You really need correct Indexed tips otherwise you'll be removing to sharpen often. Then you have the holding and making sure your concentric so collet chucks are very much prefered.

Just pay the man it's honestly not worth the trouble for the price they charge. I did post Chai's Email but Gestapo took it down.!! . . . .I'll PM you it.

[T0rnado69]

i didnt think i would be. thats why i posted the thread about it to get some input.
no collect chuck and no indexed tips or holder yet.
like you said. its not worth the hassle for the price they charge to do it.

got the email via PM thanks.

has chai got a website ?

cheers.