gregormarwick
Diamond
- Joined
- Feb 7, 2007
- Location
- Aberdeen, UK
Lathe in question is a Victor Vturn 36, which is really a carbon copy clone of an old Mori SL-35. It's a 1997 machine, good working order, but not worth a whole lot.
Noticed that we were getting bad finishes on faces, and discovered some axial play in the spindle, which amounted to a couple of thou, and was somewhat cyclic.
Got a tech in, who dicked around with it for a day and decided he wanted to pull the headstock and send it off for refurb. Quote to do so was right on the edge of economic sense, given the value of the machine.
So I pulled the spindle, and discovered that the angular contact pair had lost their preload, allowing the rear most one to spin in the housing. This in turn had worn the face of shoulder in the headstock casting (circled in red) to some degree, although it seems that most of the wear is actually on the shell of the bearing. There is no apparent wear to the diameter of either the housing or the bearing shell, so I guess it just wasn't a very tight fit in the first place.
I'm thinking poor manufacturing QA is probably the reason for this in the first place, as the shells should not have been able to spin if they were properly retained, regardless of preload.
Anyway, I'm considering options for repair. I have a new angular contact pair on order, I'm leaving the other bearings alone. The front roller bearing is taper mounted on the spindle with no easy way to remove without induction heating and/or sacrificing the bearing. There is nothing wrong with it, so I'm leaving it alone.
Problem is, the cap/labyrinth assembly is captive on the spindle until the front bearing is removed, which is a pretty horrible design IMO. Ideally, I'd be removing some material off the face of that part (circled in blue) to retain the bearing shells properly. I'm considering ways of getting that part in the lathe without removing it from the spindle right now, which is a bit tricky.
Other options that occurred to me are to loctite the rear of the bore, and fit the spindle with shims under the cap, wait for the loctite to cure, remove the shims and tighten it all up.
Thoughts?
Noticed that we were getting bad finishes on faces, and discovered some axial play in the spindle, which amounted to a couple of thou, and was somewhat cyclic.
Got a tech in, who dicked around with it for a day and decided he wanted to pull the headstock and send it off for refurb. Quote to do so was right on the edge of economic sense, given the value of the machine.
So I pulled the spindle, and discovered that the angular contact pair had lost their preload, allowing the rear most one to spin in the housing. This in turn had worn the face of shoulder in the headstock casting (circled in red) to some degree, although it seems that most of the wear is actually on the shell of the bearing. There is no apparent wear to the diameter of either the housing or the bearing shell, so I guess it just wasn't a very tight fit in the first place.
I'm thinking poor manufacturing QA is probably the reason for this in the first place, as the shells should not have been able to spin if they were properly retained, regardless of preload.
Anyway, I'm considering options for repair. I have a new angular contact pair on order, I'm leaving the other bearings alone. The front roller bearing is taper mounted on the spindle with no easy way to remove without induction heating and/or sacrificing the bearing. There is nothing wrong with it, so I'm leaving it alone.
Problem is, the cap/labyrinth assembly is captive on the spindle until the front bearing is removed, which is a pretty horrible design IMO. Ideally, I'd be removing some material off the face of that part (circled in blue) to retain the bearing shells properly. I'm considering ways of getting that part in the lathe without removing it from the spindle right now, which is a bit tricky.
Other options that occurred to me are to loctite the rear of the bore, and fit the spindle with shims under the cap, wait for the loctite to cure, remove the shims and tighten it all up.
Thoughts?