American pacemaker spindle nose

I have a 1956 c series pacemaker surplus from Boeing.
They had a monkey operating it unfortunately. The spindle nose has a lot of damage due to dirty chuck changes. Can it be unbolted and replaced without removing the entire spindle? It looks like it can.



How hard is it to regrind it? Thanks for any help you can provide.

Can't seem to get the picture straight. Sorry.

63 years of use it's going to get a bit beat up.If you grind it you will have to grind the face of the spindle as well. I would just stone any high spots and run it.

The Allen head cap screws that you see are just for holding the cam-lock cams in


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Is that a crack in the taper?

The condition of the top of the apron, the compound, and the chuck jaws suggests monkeys, not normal use unfortunately. Upon closer inspection of the picture that nose does look cracked. Should I be concerned about this? It appears to be working fine, and there are no oil leaks. I will pull the chuck back off to inspect it closer.

I was really hoping those screws held on the nose. I can see what appears to be a flat face immediately behind the camlock pin bores that has normal facing tool marks in it, not what I would expect from a boring bar. And there looks to be a step change in diameter just inside the spindle bore. I will try to get pictures of these features.

When I mount the chuck, the back of it has no clearance to the face of the spindle, and it can be pushed there by hand. Doesn't feel like the taper is engaging very well. Is this normal for a camlock? I'm new to this mounting system, hence all the questions.

Spindle nose IS the spindle. The only things that "come loose" are the cam locks

"hoping" won't make it so, the spindle nose is not removable, its part of the spindle. if the chuck is not registering on the taper, that is not good, it should. you can check with some blue after carefully stoning the high spots on both tapers.
you should also be able to get a .002 feeler gauge between the flats all around.
before making a decision on regrinding, get something with a good taper and check with that too, as the chuck taper may be worn/damaged (if you are lucky its more worn than the spindle).

Thank you for the education on the spindle. I apologize for the frustratingly stupid questions. I have checked the taper, it is 4.16ish on the largest diameter, not even close enough to try to blue check (4.188 target dimension). It is not cracked. Can I grind it down, sleeve the pilot oversize, and grind the sleeve to the correct dimensions? I have sent an inquiry to Bourn Koch about replacement parts, but I suspect the price will be impressive to say the least.

K cates said:

Thank you for the education on the spindle. I apologize for the frustratingly stupid questions. I have checked the taper, it is 4.16ish on the largest diameter, not even close enough to try to blue check (4.188 target dimension). It is not cracked. Can I grind it down, sleeve the pilot oversize, and grind the sleeve to the correct dimensions? I have sent an inquiry to Bourn Koch about replacement parts, but I suspect the price will be impressive to say the least.

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4.188 is theoretical to SHARP CORNER.

Angle per side is 7.125 degrees.

If relief in corner was .100 wide (from face), you have already lost .025" on diameter

See ASA/ASME B5.9 Spindle Noses