Ok to avoid the "screw won't come out" issue again, let me ask.....What is the object here? I am installing the long under the engine, curved shift shaft on my 75, side shift tranny. The coupling by the fire wall gives me no issues. However the one at the shift console does.

I assume you want to screw in the set screw until the shaft has NO PLAY, correct?

It ended up pretty tight, but I have no play. I guess it could it have wiggled around over the years and increased the size of the hole in the shaft.

Thoughts??

The fact that its a taper is what's locking it in there. Its a self locking taper. Think of a Morse taper on a big drill machine or the tail stock in a lathe. I just through the tool in there by hand and need a hammer and wedge to get it out.

You may think its not that tight but then its a @@#t too get out. Just did it twice this weekend myself.

Make sure the hole in the shaft is clean. If there is grease or crap in there it may feel tight but its just bottoming out on the crap and not the sides of the hole. This goes back to me doing it twice this weekend....

They are not designed to be reused and will likely loosen up again. New ones have a plastic wade that keeps them from backing out. Many recommend not using lock tight on them as it's easy to strip the hex head. If you don't want to buy new, you could try dripping some wax on the threads (has worked for me).

New ones have a nylon pin that squeezes in the threads. This acts like a nylock nut except it is a screw. I purchase 100 1/8" nylon balls from McMastar Carr. They cost about 5.00 for 100. I briefly head the cone screw. I mean briefly! the old nylon will bubble up real fast. Pick it out and press a nylon ball in it's place. Press it in using a vise. It will stick out more than a new part will, When tightening. some will shave off. It works perfect. I have done this many many times with NO problems. The only reason for me to now replace a screw is it the hex key has damaged the socket

All good points. But I am asking about the play (free twist) in the shaft after the set screw has been set. Or as a way to tell if it is, let's say, DEEP enough.

I too had a VERY tight experience and ended up cutting the cast coupler off.

Must be none! Sometimes these get loctite in place. If you don't heat them on removal, you can have problems. Any wiggle of the shaft in the coupling WILL lead to a failure. It may be the tapered hole in your shaft may be ovaled. it this is the case, it must be either repaired or replaced.

I did recently have one where the welds were cracked. This caused some movement but it was not in the coupling itself. I think these welds breaking is a common problem. It was not real apparent. The shaft was somewhat stuck in position. Only under some load could you see movement.

That is simply NOT TRUE. The cone is a slip fit, NOT a Morse taper, and the plastic locking insert in the threaded portion of the screw locks it in place. That's why we replace the screws when we have the assembly apart.

The Cap'n