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Help please

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Well I have made a couple of lathe chuck keys for my Pultra four jaw chuck out of HT socket head cap bolts and happy with the finished product, my problem was or is that I started off using the crosslide but the finish was rubbish ( more like a super fine thread than a smooth finish) I tried using indexable carbide and HSS steel but no better, tried altering speed up and down, I ended up using the hand graver as I got a much better finish , I know I only have a small Pultra instrument lathe but I should be able to get a decent finish I must admit I very rarely use the crosslide because most of what I make for antique clocks is small and I much prefer using the graver, what am I doing wrong?

John Rudd:
Crap material, tool not on centre height rubbing rather than cutting.

Blunt tool, speed too fast or slow, feed rate too fast or too slow...cutting depth too great..

A case of eliminating the above....

Also worn bearings, worn slides in need of scraping. gibs screws not adjusted or gibs worn to curves. Too much tool overhang.

Check for play throughout.

Try machining a non ferrous piece of metal, do you get same or better finish using HSS.  If I remember rightly the Pultra is a small lathe, sharp HSS tooling would possible compliment it better than insert tooling.  Having noted you tried HSS, what was your tool grind like, sharp, positive or negative rake and finish on the tool ?

A picture of the setup is worth a thousand, dodgy replies 😁 

I should also have added were you machining with coolant, oil or dry ?
Hard bolts are pretty bad for surface finish cut dry with an almost scaly finish from shearing the surface.  Especially on a small not so rigid machine as already mentioned.

Stick out !!!   How far out from the chuck was the workpiece, was it unsupported.  Turning between centres is preferable, followed by fixed steady if working away from the chuck, say 4-5 times the diameter.

I was turning between centre and for extra support I was using a fixed steady the indexable bits are this
I was using cutting oil, I think probably the bolts had something to do with it as I get a reasonable finish ( not perfect), tool on centre, I have checked the gib adjustment, donít think I had to much tool over hang but I will thank a picture of the setup tomorrow.
But thanks for suggestions so far, itís not something I do very often but it would be nice to understand why.


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