Holding Lead Screw in lathe chuck?

[raynerd]

Hello, I want to turn down a section of a lead screw in the lathe but I`m concerned about damaging it in the chuck jaws? Should I be concerned about this? I`m guessing it is steel so shouldn`t mark and the threads are quite chunky but I just wanted to make sure as I can`t afford to ruin it.

Chris

[Bluechip]

Shove a slice of drinks can beteween the L/Screw & jaws ... 

Soft Ally usually.

BC

[BillTodd]

Just insert a small piece of copper or aluminium between the 4 jaws .

If you are using a 3 jaw: wrap a thick-ish piece of ally around a similar sized bar, grip that in your chuck (space the gap appropriately) then bore it to a close fit to the lead-screw  - don't remove it from the chuck or mark its position well, before inserting the lead-screw

Bill

[joegib]

You don't say what kind of leadscrew you're machining. If there's any significant length extending out of the back of the lathe spindle, only carry out machining at low RPM (backgear) or you'll get a bad case of 'whip'. Sorry if I'm stating the obvious.

Joe

[Country Bubba]

The ones I did for a router, I simply chucked them up in a 5C collet. This will grip it tightly and leave no marks. When I did some really hard ball screws for my mill/drill, didn't have the 5C so used the 4 jaw with no extra protection. Those things are HARD

[pete3000]

offering another soft grip solution, aluminium duct tape, aka builders tape. Used for sealing vent ducts and insulation joints etc on hevac syatems, cheap enough and sticks to most surfaces. It is thin enough and made from thin 30 or 40 micron soft aluminium. Wont slip very easily

Pete

[Tony Wells]

Plumbers copper tubing large enough to slip over the leadscrew, then slit one side with a saw. Two cuts if needed to make a gap wide enough collapse enough.

[raynerd]

Hi Guys, despite playing at engineering for the last 3-4 years, I`m still scared of my 4 jaw! However, I took the plunge last night and managed to get it nicely centred with some ally drinks can shims. Seems to have worked very well. Thanks for all the ideas.

I like the split collet idea of using a slitted copper tubing. I`ve held delicate clock arbours like this so I don`t know why I didn`t think of that.

Thanks again for all the quick replies yesterday.

Chris

[Fergus OMore]

Chris,
           Most of the 4 jaw problems are caused because most people have only ONE key to adjust the opposing jaws.

Simply make up  a spare set-- and life will become far easier.

However, if you make up a set of throwaway 'soft jaws' for your three jaw, you get repeatable accuracy but only in one diameter.

Cheers

FOM

[pete3000]

try and use older copper tubing, the newer stuff isn't proper copper. It looks ok but has a steel/nickel content, which is harder, the new 2p coins after 1992 are copper plated steel alloy, try it with a magnet.

the older 2p coins and older copper pipe are purer in copper content Just shows you older is better in more ways than one. I heard recently alternators and motors are now being produced using ally windings as it's 5-6 times cheaper than copper.