Jacobs 33 Male Taper Repair

[Mustangmarty1967]

I’m restoring a Delta 17-990X and need some help. The runout on the spindle just above the male Jacobs 33 taper is practically zero. But at the bottom of the taper, the runout is .011. Can this be resurfaced somehow to true it up?

 

[markba633csi]

Does the spindle have a removable arbor? If so then you would just remove and replace it

 

[ChazzC]

Are you comparing the OD of the spindle with the ID of the JT socket inside the spindle?

 

[whitmore]

The jacobs taper surface is (when assembled) well protected; such runout suggests the spindle shaft is bent.
Maybe with a lead hammer you can straighten it.

 

[Mustangmarty1967]

Does the spindle have a removable arbor? If so then you would just remove and replace it

No. It is a male Jacobs 33 taper that is part of the whole spindle, but on the bottom end.

 

[Mustangmarty1967]

Are you comparing the OD of the spindle with the ID of the JT socket inside the spindle?

It doesn’t have a socket inside the spindle. It’s a male bottom end of the spindle. I added a pic. I’ve seen male Jacobs 33 reamers to true up JT33 sockets (female), but I haven’t found any such tool, but female, to true up a male taper. I would love for it to be a female MT2 socket, if there were a way to do that.

 

[Alexander McGilton]

The manual makes no reference to there being a Morse tapper to utilize and replace the arbor.

As said before there could be a bend on the spindle. I'm thinking that it could have been that bad from factory.

If you have a lathe big enough. I would have isolate the quill assembly, insert it to the four jaw, alight it to the outer profile of the quill, place a lathe dog on the spindle shaft to one of the jaws, then turn a new tapper on to the Jacob's taper.

 

[markba633csi]

I think I can see the bend in the photo- looks bad. Probably you would have to disassemble the whole thing and try to straighten
the spindle with a hydraulic press. Maybe recut the taper in the lathe. Worth the trouble? Can't say

Odd that the spindle appears to have a threaded (retaining?) area up above- but most drill chucks have no such retainment
I wonder what the intention was? Maybe the OEM chuck had such a retainer? Beats me

 

[ChazzC]

No. It is a male Jacobs 33 taper that is part of the whole spindle, but on the bottom end.

Sorry, original post photo wasn’t showing up.

It appears that if you drive out the roll pin the JT arbor could be removed and replaced. You may need to start with a JT33 to MT or straight shank arbor to make a replacement.

 

[Jake M]

That's in rough shape for sure.

Were that mine, the first thing I'd do is clean the thing as well as you can. Then color the WHOLE thing with a sharpie. With plenty of time for that to dry, turn on the drill, and starting at the top, moving to the bottom, GENTLY, run a fine stone down it. 600, 800, 1000, something very fine. And don't well. The ONLY purpose of that is to "mark" the high spots, IF the high spots match up to where there's errors as gross as 0.012 inches, then you "Probably" could gently stone those down some. And if the inside of the chuck looks like it's the culprit that went around that taper (probably repeatedly), then the chuck needs replacement. I've patched up several to very acceptable runout for a drill press, by just this method. I've also had fails. It depends what happened, how bad it is, what "else" happened, all that stuff. But the blue, the stone (lightly, just to find high spots), and your micrometer all work together to paint a picture of exactly what the damage is.

This is NOT a guaranteed fix, however, it's served me well. That spindle has had a hard life, I'm NOT suggesting trying to regrind it in place, but if the boogered up raised spots came down to the "global average", you are in no way compromising it's ability to be reground or repaired. The little "hollows" won't bother, it's the high spots that prevent it from staying in place.

Again, gently and carefully. You will NEVER reshape that with a stone. And if it's truly bent, you will NEVER straighten it with a stone. You'll actually make it worse. Stoning is for individual high spots. only.

You may or may not know this, but that thread on there is for a Jacobs 33C. That's a 33 taper plus a locking collar. They were put on drill presses that were pushing the edge of what that size taper should be used for. The last chuck out there which has that feature is a Jacobs model 34-33C, and the prices are all over the map. If you end up needing one, check EVERYWHERE. Prices are all over the map, and constantly changing, which smells terribly of obsolescence and old stock drying up.