Repair suggestions for lathe compound lock pin

[Friendly non murdering Sword]

Most lathes' compound have a locking feature that engages with a hole in the underside of the toolpost/QCTP and that prevents rotation of the toolpost/QCTP during heavy cuts. On my lathe I only ever need this locking pin once or twice per year. I had to do some heavy internal threading were in the past I had problems with the QCTP rotating so I tried to get the pin engaged in the QCTP.

I already had the problem in the past that the spring loaded pin was stuck a bit in its hole and it had to be loosened with a hammer. But this time the hardened pin has duck/wedged itself in the soft cast iron in a way that was impossible to get it out. Since its also a blind hole my last resort was unfortunately to remove most of the pin on the mill until the rest came out. The original bore in the cast iron is still intact. (What looks like a crack at the top of the hole is only swarf)



So I was wondering how I best fix this... using a hardened pin again in soft cast iron will most likely result in the same outcome over time. I could press in a hardened bushing and then use a hardened pin. But maybe someone has a completely different solution for locking the QCTP during heavy cuts that might work better? The QCTP I use is a Dickson clone.

 

[Jimsehr]

I think I would drill and tap all the way thru then leave a set screw in the bottom and if you have this problem again use set screw to push hard pin out and replace when needed.

 

[benmychree]

I have had the same problem, but no pin or hole was provided; the problem is simply solved by tightening the QCTP tight enough to prevent rotation, my lathe has a T slotted compound rest, so no easy thing to locate a locking pin and hole at the normally used angular position.

 

[RaisedByWolves]

I have had the same problem, but no pin or hole was provided; the problem is simply solved by tightening the QCTP tight enough to prevent rotation, my lathe has a T slotted compound rest, so no easy thing to locate a locking pin and hole at the normally used angular position.

I made a plinth for my lathe to remove the compound and ground it flat/parallel.

I ground it so nice that the tool post would not stay put regardless.

I put a small dab of 220 grit clover compound between them and it locked them tight.

If you don’t have clover compound at hand some of the grinding dust from your bench grinder may suffice.

Now I’m sure there are a few people gasping in horror over putting grit/compound on their machine, but trust me, unless you're ham fisted and apply it like toothpaste it won’t migrate.

Over time this will slightly roughen and lap both surfaces and allow them to naturally grip each other with moderate tightening.