My own fault for being cocky.
I needed a new bearing piece for the mandrel on my horizontal mill - a spacer that sits in the lubricated bronze bush in the mandrel guide. Using some scrap en40 shaft I've had kicking around for ages, 3 inch dia, machining down to just over 2inch. The 13 inch length was too big to go into the lathe spindle, so using an existing tapped hole in the end, was spun between the chuck and live centre. I carefully machined it down to size, including a section to allow the fixed steady (on the Colchester Triumph) to hold the work while it was being bored.
it all went swimmingly, outer, inner and end machined. So I had to part it. I have a Tizit parting tool, with newish tip fitted. Set it up, speeds, feeds etc, using heating oil coolant, auto feed (mistake 1?). What I didn't do was re-engage the tailstock in the newly bored hole in the end (mistake 2?). Anyway it was parting beautifully, not chattering or grumbling in any way.
Suddenly there was a bang, and whether I stopped it or it stopped itself, the lathe stopped, with the length of en40 at an awful angle, the top finger of the steady given way, bent adjuster etc, the lathe chuck was still in one piece, the parting tool and holder was boogad, having gouged the nearly finished job...
So what went wrong? I guess the parting tool jammed, maybe from swarf jamm, or perhaps the cross feed gibs were too slack, allowing it to be drawn in? Maybe the height of the tool was a touch low, which becomes more critical the smaller the diameter? Whatever, the work should have also been supported by the tailstock, until nearly the last few though.
No pictures, I was too p***ed off...
I needed a new bearing piece for the mandrel on my horizontal mill - a spacer that sits in the lubricated bronze bush in the mandrel guide. Using some scrap en40 shaft I've had kicking around for ages, 3 inch dia, machining down to just over 2inch. The 13 inch length was too big to go into the lathe spindle, so using an existing tapped hole in the end, was spun between the chuck and live centre. I carefully machined it down to size, including a section to allow the fixed steady (on the Colchester Triumph) to hold the work while it was being bored.
it all went swimmingly, outer, inner and end machined. So I had to part it. I have a Tizit parting tool, with newish tip fitted. Set it up, speeds, feeds etc, using heating oil coolant, auto feed (mistake 1?). What I didn't do was re-engage the tailstock in the newly bored hole in the end (mistake 2?). Anyway it was parting beautifully, not chattering or grumbling in any way.
Suddenly there was a bang, and whether I stopped it or it stopped itself, the lathe stopped, with the length of en40 at an awful angle, the top finger of the steady given way, bent adjuster etc, the lathe chuck was still in one piece, the parting tool and holder was boogad, having gouged the nearly finished job...
So what went wrong? I guess the parting tool jammed, maybe from swarf jamm, or perhaps the cross feed gibs were too slack, allowing it to be drawn in? Maybe the height of the tool was a touch low, which becomes more critical the smaller the diameter? Whatever, the work should have also been supported by the tailstock, until nearly the last few though.
No pictures, I was too p***ed off...