- Joined
- Dec 5, 2017
- Messages
- 464
My Seneca Falls Star 30 lathe is 100+ years old as near as I can tell. Given that, it's in pretty good shape, but the 3 jaw chuck has horrible runout: .030+ with a precision ground pin chucked up, measured as close to the jaws as I dare.
Runout at the body of the chuck near the spindle is .002 give or take, so the problem is in the scroll/jaws. It has a somewhat oddball spindle nose both in diameter and thread pitch, so a new chuck would require machining a new back plate, which I have neither the tools, the experience nor the courage to attempt.
Watched the mrpete222 (tubalcain) video where he used a tool post grinder to true up the jaws with excellent results and thought I'd try that.
The first task was to obtain a tool post grinder. Not something I foresee using a lot so couldn't see going top dollar for one, so I picked this one up off Fee Bay:
I was a little upset to find that the "motor" was a Harbor Freight router! The adapter to mount it on my AXA tool holder was very nicely machined and the router was variable speed, so I figured for the price, what the hey. A Du-All it ain't, but it's good enough for a junkyard machinist. Had to order some 1/4" shank grinding stones to use as well.
The QCTP adapter hits my compound (you can see it sits a little proud of the tool post) but that put it pretty close to on center so I went with it. I'll need to modify the adapter later so I can adjust it dead nuts if need be.
Then I had to make a ring to lock the jaws with. Started with a nice piece of 4" Schedule 80 pipe. Ooops, doesn't let the jaws open wide enough to take the stone. Poop. Hey, here's a nice piece of 6"...cut a ring off that and....oooops, now the jaws don't open far enough to lock on the ring. Rats. Rummage around in my cultch pile without much hope of finding anything when I came across a piece of 5 inch Schedule 80. Cut a ring off THAT and "Say, that should work!" Except that the thickness of the pipe wall blocked the outer bolt hole on the jaw. Fortunately, I have a mill, so I marked the spots on the ring that needed to be relieved and notched them with a 3/8" end mill (jaw bolts are 5/16")
Got everything mounted and aligned and very gingerly started kissing the jaws with the grinding stone and the chuck running in opposite directions (sure glad I took the time to wire up that reversing switch a couple of weeks ago...) Things seemed to be progressing okay until I started getting a LOT of vibration. What the...oh. The stone was mounted to the mandrel with a screw which had come loose, and the router was mounted to the tool post adapter with set screws, which had ALSO come loose. Put locktite on all the fasteners, realigned everything and went back to grinding. Slllooooooow and easy. Advance the stone a couple of thou, make several passes in and out, advance, rinse, repeat.
I knew my #3 jaw was the loosest, so I worked it until it was just kissed all the way across. Runout now is ~ .008 which is still bad, but WAY better than it was. I'll set up and polish them a bit more as I can still see a dull spot on the #3 jaw. I quit at that point because I wanted to make sure I was making things better, not worse and I had to take the setup down to chuck up the pin and re-indicate.
Overall, I'm pleased with the outcome, especially given my cheesy equipment and lack of experience. Turned a piece of 1" stock with nice results, faced it, bored a hole in it and even got my cutoff tool working like it should. Life is good...
Runout at the body of the chuck near the spindle is .002 give or take, so the problem is in the scroll/jaws. It has a somewhat oddball spindle nose both in diameter and thread pitch, so a new chuck would require machining a new back plate, which I have neither the tools, the experience nor the courage to attempt.
Watched the mrpete222 (tubalcain) video where he used a tool post grinder to true up the jaws with excellent results and thought I'd try that.
The first task was to obtain a tool post grinder. Not something I foresee using a lot so couldn't see going top dollar for one, so I picked this one up off Fee Bay:
I was a little upset to find that the "motor" was a Harbor Freight router! The adapter to mount it on my AXA tool holder was very nicely machined and the router was variable speed, so I figured for the price, what the hey. A Du-All it ain't, but it's good enough for a junkyard machinist. Had to order some 1/4" shank grinding stones to use as well.
The QCTP adapter hits my compound (you can see it sits a little proud of the tool post) but that put it pretty close to on center so I went with it. I'll need to modify the adapter later so I can adjust it dead nuts if need be.
Then I had to make a ring to lock the jaws with. Started with a nice piece of 4" Schedule 80 pipe. Ooops, doesn't let the jaws open wide enough to take the stone. Poop. Hey, here's a nice piece of 6"...cut a ring off that and....oooops, now the jaws don't open far enough to lock on the ring. Rats. Rummage around in my cultch pile without much hope of finding anything when I came across a piece of 5 inch Schedule 80. Cut a ring off THAT and "Say, that should work!" Except that the thickness of the pipe wall blocked the outer bolt hole on the jaw. Fortunately, I have a mill, so I marked the spots on the ring that needed to be relieved and notched them with a 3/8" end mill (jaw bolts are 5/16")
Got everything mounted and aligned and very gingerly started kissing the jaws with the grinding stone and the chuck running in opposite directions (sure glad I took the time to wire up that reversing switch a couple of weeks ago...) Things seemed to be progressing okay until I started getting a LOT of vibration. What the...oh. The stone was mounted to the mandrel with a screw which had come loose, and the router was mounted to the tool post adapter with set screws, which had ALSO come loose. Put locktite on all the fasteners, realigned everything and went back to grinding. Slllooooooow and easy. Advance the stone a couple of thou, make several passes in and out, advance, rinse, repeat.
I knew my #3 jaw was the loosest, so I worked it until it was just kissed all the way across. Runout now is ~ .008 which is still bad, but WAY better than it was. I'll set up and polish them a bit more as I can still see a dull spot on the #3 jaw. I quit at that point because I wanted to make sure I was making things better, not worse and I had to take the setup down to chuck up the pin and re-indicate.
Overall, I'm pleased with the outcome, especially given my cheesy equipment and lack of experience. Turned a piece of 1" stock with nice results, faced it, bored a hole in it and even got my cutoff tool working like it should. Life is good...
