Question On How To Make An Mt3 Socket?

[John Hasler]

I'm sure I'm probably way of base on this, but wouldn't it make sense to start with an oversize o.d. and then once you have created and lapped in the socket remount the piece on a known good male taper and correct any run-out/concentric issues at that point? Mike

That would be a good idea, but at this point we are trying to set the angle correctly from the reference taper. It's axis must be in the same vertical plane as the lathe axis.

 

[rgray]

I'm sure I'm probably way of base on this, but wouldn't it make sense to start with an oversize o.d. and then once you have created and lapped in the socket remount the piece on a known good male taper and correct any run-out/concentric issues at that point? Mike

That is how I did it.
Just recently got a cylindrical grinder that does a real nice job of correcting the od after heat treat and finishing the Id.

 

[kizmit99]

Think about what happens when you offset the tailstock to cut a taper.

Yes - ok, I see that now. Thank you!

Set up again, without the tailstock. Using your DTI rotate the taper until the point of maximum runout at the far end is on the top. Then indicate your angle off the side.

Will do.

Tracing the taper from a line that isn't parallel with the axis of the cone will also result in an error, now THAT is a parabolic section! I remembered Geometry!

I'm pretty sure they hadn't invented any of that fancy stuff when I took Geometry. At least that's my story, and I'm sticking to it!

I'm sure I'm probably way of base on this, but wouldn't it make sense to start with an oversize o.d. and then once you have created and lapped in the socket remount the piece on a known good male taper and correct any run-out/concentric issues at that point?

Yes, I suspect overall that would have been easier to make the whole part in a single setup on the lathe... but at this point the mating part is already bored to the OD of the part I'm cutting the socket in.

Worst case I'll remake both parts, but for now I don't think that's necessary.

 

[kizmit99]

I verified the compound angle as suggested. I did not need to adjust the compound at all, so if I'm following correctly, that simply means that my tailstock was already centered on the lathe axis, and the hole in the end of the center I was using as a gage was centered on the taper axis. So in the end both methods ended up achieving the same result, but I guess the method suggested removes the variable of whether or not the tailstock is on center to begin with.

I then rechucked the part in the 4-jaw, painstakingly got it all centered and straight again, then realized I had the small end sticking out... So flipped it, then re-centered and straightened again. I had to adjust the attack-angle on the cutter a bit to get where I could plunge the boring bar through to the small end of the taper. The first pass, just removing a very small amount of metal (at the large end of the taper) reduced the tool runout from .007 to .003. A second light pass brought it down to about .0015. A third pass didn't improve it anymore, so I called it quits. I think that will be good-enough for what I'm using this for anyway. A little over .001 slop is quite a bit better than the .025 I started with.

Thanks for all the help!