Lathe head alignment

[Larry$]

Here is a description of my procedure.

Went back and read it.
My lathe weighs about 2700#s, sits on the 6 factory supplied leveling bolts & pads, No issues with wondering about.
I haven't checked for concavity with a face plate, good idea.
I was getting so hot & tired that I was trying to get it done. I had recently re-checked front to back twist with my very good level and adjusted it slightly. To get uniform pressure on all bolts I've used crow's foot sockets on my torque wrench. Not so sure that's any better than just the "feel." Didn't check end to end level as I don't really care about that. Whatever it still is from the original setup is what it is.

Did you take spring passes after your cuts?

I did on the first few iterations but had found no measurable changes so I didn't on the last half dozen tries.
I need to go back and check see which end was larger. Why does it matter?
Even getting slightly different tensions on the push/pull adjusting bolts affected the rotation of the head. Or maybe it was how snug I had the mounting bolts while trying to make adjustments? Having to take the change gears and banjo off/on for each try was a PIA.

At any rate I need to go back over everything when its not so damn hot and I'm not exhausted. Then move on to the tailstock end adjustments. Thanks for the input guys.

 

[ddickey]

I believe it has to do with tool pressure/deflection during a cut.
See Pg. 53 figure 8. Then reference 8b on the next page. https://springfieldarsenal.files.wordpress.com/2018/10/schessinger_testing_machine_tools.pdf
Wes shows it in his video here ~ 10:30

 

[Larry$]

I attempted to reduce the side force when cutting by using sharp, almost pointed HSS, not carbide inserts. I had a 2 " diameter 12L14 bar sticking out about 7" from a heavy 8" chuck. I seriously doubt that there was measurable deflection. The tool was sticking out of the holder less than .5" The compound was back and locked, the cross slide was locked. 640rpm .005 DOC, .0008 feed per rev. Cutting oil lubed. I was producing nice but small C or 6s chips not Xmas tree decorations. Measurable deflection? I'll give it another go when it isn't so hot.

 

[Larry$]

This morning I did all my measuring, rechecked the bed for twist. I concluded my results were likely as good as it is going to get, with me at the controls.

 

[Larry$]

Now how about the 2 collar test?

Just finished that. The tailstock was off a bit. Now corrected as good as I can.
That completes the lathe improvement project. The problem now is .... I can't blame the lathe for some of my less than ideal results.