- Joined
- Dec 2, 2010
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My vintage Rockwell 11" lathe has had tailstock droop since I got it and drilling very small holes accurately has been a real problem. Holes, especially in softer material, come out oversized and misaligned, so after reading several posts here and elsewhere I decided to bite the bullet and attempt a repair. After take a few measurements I decided that nearly all of the wear was on the tailstock casting and not the ram.
After considering several approaches, I decided to make an oilite bronze bushing for the nose of the casting. Rather than remove the tailstock and attempting to bore it in my mini-mill, I decide to bore it in place.
I figured this would give me the best alignment. The approach I used was to mount the tailstock betweeen the headstock and the carriage, mount my boring head in the spindle, gently clamp down the tailstock with the locking clamp, and then push the tailstock toward the spindle with a very slow feed rate using the power feedscrew. The boring tool was adjusted to take only .005" of stock on each pass. This appeared to work quite well, as it felt like the tailstock was quite stable while the material was being removed.
With that step complete, I then turned down an oilite bushing with an OD to match the bore on the tailstock casting and rough ID only, about 0.030" smaller than the ram, and then mounted the bushing into the tailstock with threadlock and let it dry.
After the threadlock set up, I then completed the ID taking only .001" off at a time and checking the fit. Once the ID was completed, I put everything back together and indicated the inside of the MT3 taper in the ram. Everything appears to be within .001".
I then chucked up a rod, and attempted to center drill it - for the first time, no walking of the bit. Success. Thanks to all who posted their approaches to this problem, as without seeing other approaches, I would have had no idea where to begin.
Paul
After considering several approaches, I decided to make an oilite bronze bushing for the nose of the casting. Rather than remove the tailstock and attempting to bore it in my mini-mill, I decide to bore it in place.
I figured this would give me the best alignment. The approach I used was to mount the tailstock betweeen the headstock and the carriage, mount my boring head in the spindle, gently clamp down the tailstock with the locking clamp, and then push the tailstock toward the spindle with a very slow feed rate using the power feedscrew. The boring tool was adjusted to take only .005" of stock on each pass. This appeared to work quite well, as it felt like the tailstock was quite stable while the material was being removed.
With that step complete, I then turned down an oilite bushing with an OD to match the bore on the tailstock casting and rough ID only, about 0.030" smaller than the ram, and then mounted the bushing into the tailstock with threadlock and let it dry.
After the threadlock set up, I then completed the ID taking only .001" off at a time and checking the fit. Once the ID was completed, I put everything back together and indicated the inside of the MT3 taper in the ram. Everything appears to be within .001".
I then chucked up a rod, and attempted to center drill it - for the first time, no walking of the bit. Success. Thanks to all who posted their approaches to this problem, as without seeing other approaches, I would have had no idea where to begin.
Paul
