01-18-2020, 10:13 AM
(01-24-2019, 01:04 AM)castellated nut Wrote: For whatever reason occurred to me at the time i resolved to have a right hand thread on one end and a left hand thread at the other end, and with the confidence misplaced by the experience with the back plate decided to undertake the more difficult of the two tasks, that is to turn a left hand thread on a spindle threaded back plate chuck with no other locking mechanism save the seized back plate. So off to the Nuts and Bolts supplier for a 1" nut (about eight dollars two years ago) whereupon I returned with a left hand nut.
If you don't put the left hand thread on the draw bar end, then it will tend to unscrew itself during rotation. I made a draw bar for my lathe, but that little voice didn't tell me to put a left hand thread on the end. Once I discovered my error (the nut fell off during operation), I ended up putting a second nut to lock the first. I intend to remake the draw bar with the correct threads. I make my nuts from hex stock, so I had to order a LH tap for my thread.
You say that the reason for the seized chuck can be seen in the pictures. Okay, where? Did you find swarf under the threads at disassembly?
I take it that you removed the chuck from the backplate, then turned the backplate to dust. Did you use forward rotation, or reverse? I wonder if reverse rotation would eventually loosen the remains of the backplate.
A trick that the British Navy machinists used to use to minimize stuck chucks, was to cut a washer from wax paper or parchment paper (cooking paper) and place that between the spindle shoulder and the chuck. My spindle thread is the same as yours and it really works. Mind you that it won't help if there is swarf in the threads and you "power" thru them to seat the chuck.