Question about small parts on the lathe

[pelesl]

Basic question about turning a part:

I am making a small part that has a 3/16" diameter that steps down to 1/16" diameter. The 1/16" part is about 3/8" long.

I have tried a couple of times now and I end up with a taper on the 1/16" section. At the "free" end, it's about 3 or 4 thousands larger in diameter than at the "connected" end. I know this is due to improper technique/bad tools. I've tried a couple of things, including making sure my tool height was dead on center---that improved things a bit. The cutter I'm using is the type with inserts, and the insert is relatively new. Material is 303. The lathe is running at 1200 RPM.

So how do you machine straight on a lathe on such a small diameter if you can't put a live center on the free end?

[Dennis Rech]

I would start with a 3/16" rod that is 1/4 inch too long.
I would support the right end with a dead center and machine the 1/16" portion to size and then cut off the excess 3/16" portion.

[will gilmore]

The taper is caused by the free end deflecting away from the tool. Aside from supporting the free end (above is a good idea) having an extra sharp tool (lots of rake) and taking light passes will help.

[Geof]

Machining 303 that diameter, that length and only getting a 4 thou taper is good; there is nothing wrong with your technique.

It is possible you could improve it by using a very sharply ground HSS tool, carbides do not have a really razor sharp cutting edge and they always exert more force on the workpiece than a really sharp HSS tool.

[kentucky jeremy]

add in an x movement at the connected end of your prog. and tell it to feed up then offset tool down to reach size disired