BoxcarPete
Stainless
- Joined
- Nov 30, 2018
- Location
- Michigan, USA
Alright fellas, I need some help here.
Yesterday, I crashed my lathe. I was running an interrupted cut up to a shoulder, went one rev too far, BAM, tool digs in, ejects my part, and manages to unscrew the toolpost. The handle whipped around, right into the chuck jaws. Explodes the knob on the end and bends the handle. Toolpost otherwise looks OK. Miraculously, the cutting tool itself survived as well, as did my part (I was cutting acetal at the time, and the cutting tool only dug into the bit that I still needed to cut).
After that, I rotated the spindle by hand. Seemed to spin freely, without making any hideous noises. Seemed to run under power without issue as well. I chucked up a bar without noticing anything suspicious in the 4-jaw centering process. Once I made a cut, however, it became clear that something was going on. The spiral surface roughness pattern doesn't show up in the picture as starkly as it does in real life. The bar also has a repeating runout pattern, 0~.005~0.0005~.0055~0... I didn't check to see if it spirals around the part like the roughness pattern, but I did check a few points and it is consistent across the surface.
It was getting to be the end of the day, so I decided to call it quits once confirming that there was something serious going on. That said, based on the current information, anyone have some guesses as to the cause? Next steps? Remember, that runout pattern was over 5 thou on a cut bar, not the lathe spindle itself. Lathe is a 1968 19" Leblond Regal. Recommendations to scrap the tool will be unwelcome but considered, if worse comes to worst.
The only thing I can think of other than bearing damage or a bent spindle would be that when I went to ensure that the chuck was still tight, I inadvertently loosened it (L1 always seems backwards to me), then re-tightened immediately. I doubt that would show up as runout on a cut surface if I had entrapped something there though.
Yesterday, I crashed my lathe. I was running an interrupted cut up to a shoulder, went one rev too far, BAM, tool digs in, ejects my part, and manages to unscrew the toolpost. The handle whipped around, right into the chuck jaws. Explodes the knob on the end and bends the handle. Toolpost otherwise looks OK. Miraculously, the cutting tool itself survived as well, as did my part (I was cutting acetal at the time, and the cutting tool only dug into the bit that I still needed to cut).
After that, I rotated the spindle by hand. Seemed to spin freely, without making any hideous noises. Seemed to run under power without issue as well. I chucked up a bar without noticing anything suspicious in the 4-jaw centering process. Once I made a cut, however, it became clear that something was going on. The spiral surface roughness pattern doesn't show up in the picture as starkly as it does in real life. The bar also has a repeating runout pattern, 0~.005~0.0005~.0055~0... I didn't check to see if it spirals around the part like the roughness pattern, but I did check a few points and it is consistent across the surface.
It was getting to be the end of the day, so I decided to call it quits once confirming that there was something serious going on. That said, based on the current information, anyone have some guesses as to the cause? Next steps? Remember, that runout pattern was over 5 thou on a cut bar, not the lathe spindle itself. Lathe is a 1968 19" Leblond Regal. Recommendations to scrap the tool will be unwelcome but considered, if worse comes to worst.
The only thing I can think of other than bearing damage or a bent spindle would be that when I went to ensure that the chuck was still tight, I inadvertently loosened it (L1 always seems backwards to me), then re-tightened immediately. I doubt that would show up as runout on a cut surface if I had entrapped something there though.