Glenn Brooks
Aluminum
- Joined
- Nov 16, 2014
- Location
- Woodinville, Wa
I volunteer in the back shops for the Hawaii Railway Society, where we have an old 18” x 72” Cincinnati tray top lathe (with an old school lantern tool post and HSS tooling), that I occasionally use. Currently we are replacing a traction motor on a WWII vintage GE 44 tonner road (locomotive). My requirement was to turn a 2”x8”pin out of some 2 1/4” 4140 round stock.
The pin holds a 2000# traction motor up into a spring buffered mounting bracket on one of trucks - so not exactly a precision surface.
In making the pin, I had a terrible time getting an acceptable finish on the round stock (using HSS tooling). The rough finish was cottage cheese texture during roughing turning, even though I cleaned up and sharpened the tooling nearly every pass on the work. I finally got a marginally acceptable bearing surface with two shallow finish passes (DOC .005”, at 96 RPM/.0035”feed rate. However the final finish cut left multiple concentric tooling marks where the tooling penetrated an easy 2-3 thou deeper than the rest of the finish surface.
Wondering if this is a just a function of turning 4140 with HSS tooling, my operator error, or perhaps might the cross feed screw be to wornout to hold the compound rest and tool holder consistent with the axis of the lathe?
Thanks for any comments.
Glenn
The pin holds a 2000# traction motor up into a spring buffered mounting bracket on one of trucks - so not exactly a precision surface.
In making the pin, I had a terrible time getting an acceptable finish on the round stock (using HSS tooling). The rough finish was cottage cheese texture during roughing turning, even though I cleaned up and sharpened the tooling nearly every pass on the work. I finally got a marginally acceptable bearing surface with two shallow finish passes (DOC .005”, at 96 RPM/.0035”feed rate. However the final finish cut left multiple concentric tooling marks where the tooling penetrated an easy 2-3 thou deeper than the rest of the finish surface.
Wondering if this is a just a function of turning 4140 with HSS tooling, my operator error, or perhaps might the cross feed screw be to wornout to hold the compound rest and tool holder consistent with the axis of the lathe?
Thanks for any comments.
Glenn