Lathe setup for gun work

[skelso]

I posted some general threads about the woes I've been through in setting up my lathe after moving it cross country. I've finally gotten everything together and done the 2 collar test. I was able to get within .002 - .003 over 6" before I ran out of adjustment on the feet.

I'm posting this here because while I feel that is good enough for most hobby work, I really don't know if it's good enough for gun work or if I need to continue to chase that last .001.

I will say I am not convinced it's a bed twist issue. The surface finish on the unsupported end is a lot rougher than the headstock end. This indicates some flex, somewhere, to me. (I did take 3 spring passes to get to a point where the tool traversed the length but did not cut).

The lathe is a Romi/Doall 13x20 w/ BXA QCTP, 1/2" HSS tooling.

The test bar was a length of 2" aluminum.

Thoughts and suggestions welcome.

Thanks!

 

[mfim]

Hi What size bore is thru your headstock?

 

[dave2176]

Use a machinist level across the ways to take the twist out of the bed and achieve some resemblance of level, front to back and lengthwise. Turn the stock as you did, unsupported at the tailstock end, this will tell you if the spindle is in align with the bed. If not, hopefully you can rotate the headstock on the bed to correct it. Final step is to turn a piece between centers and adjust the tailstock alignment so both ends are the same diameter.

Dave

 

[skelso]

Hi What size bore is thru your headstock?

Don't remember exactly. 1-1/2 or 1-9/16.

Use a machinist level across the ways to take the twist out of the bed and achieve some resemblance of level, front to back and lengthwise. Turn the stock as you did, unsupported at the tailstock end, this will tell you if the spindle is in align with the bed. If not, hopefully you can rotate the headstock on the bed to correct it. Final step is to turn a piece between centers and adjust the tailstock alignment so both ends are the same diameter.

Dave

Dave, thank for the reply. I had leveled with a Starrett 98 and adjusted during the 2 collar test but at the time of my original post I could not get any better than .002 -.003.

Since then, I posted the question in the metrology forum and the replies revealed I was using the wrong foot to dial it in. Last night I was able to get it within about half a thousandth.

Now on to the next steps...