I've been thinking about a lathe spindle-bore stop for a while, but had no "3AM epiphanies" waking me up. Then I saw a post on another forum of maybe using a Harbor Freight exhaust pipe expander. Seemed ideal. The small one would fit my spindle bore.
http://www.harborfreight.com/automotive-motorcycle/exhaust/small-tail-pipe-expander-69550-9156.html
The original threaded rod in the expander is 12x1.5mm with a 17mm nut. A 7/16-14 rod with a 11/16 nut is a perfect replacement. I decided a hollow threaded-rod with a smaller threaded rod through it would work for a stop. So, a 7/16-14 hollow threaded rod ??? Junk box to the rescue. A 1/8" black pipe has a slightly smaller O.D. than a 7/16-14 thread and has a slightly larger I.D. than a 1/4-20 rod. I decided that one expander would be a hassle to use, so I went with two, one on each end of the spindle bore. Ran a die down each end of the 1/8" pipe, far enough to have a nut and jam nut at the end of the expander. This acts as a fixed stop for the inboard end of that expanders. The 1/4-20 rod needed a way to be centered, adjusted, and locked. I made two threaded caps for the threaded pipe. Drilled one for clearance of the 1/4-20 rod. The other was drilled and tapped for 1/4-20. A nut on the rod on the left end of the spindle allowed for stop-depth adjustment and locking. Tightening the outboard nuts on the expanders, over the extended 1/4 -20 rod and caps was a problem. Too much for even deep sockets. Since not much torque is needed, I bored a 11/16 socket a much as possible and brazed it to the end of a piece of 3/4" electrical conduit...and now I have a "very" deep socket.
So you slide the assemble into the spindle, hold the left end of the pipe while using the deep socket to expand the chunk-end expander. Then use the socket to expand the one in the other end. Now you can loosen the 1/4" jam nut, screw the 1/4" rod in or out to set the stop depth, and tighten the nut. The concept was for short stock in the chuck. The length of the 1/8 pipe could be changed if you want the stop to be deeper in the spindle. Still trying to think of an easy way to use just one expander.
spindle bore stop
Ken
View attachment 90958View attachment 90957View attachment 90959View attachment 90960