Well, seems my “bargain” 16N is pretty worn

[great white]

I recently bought a couple jacobs chucks in various states of neglect. One was a jacobs 16N super chuck.

I took it apart and cleaned off a lot of the abuse with a light skim off the external surfaces.

The jaws showed some wear, but seemed to clean up nicely with a little stoning.

I’ve had it apart a couple times now, chasing the runout.

I don’t even want to talk about what it was when I got it, seeing it was stupid high in the 0.1” to 0.2“ range.

I indicated the JT3 in the drill press and got a tir about 0.0005”. Nothing bad there!

Then I mounted the bare body in the lathe and zero’d it out on the sleeve ring on the body. Then moved to the JT3 taper in the chuck body. Indicated about 0.004”. Not great, but not horrible. Oddly enough, it showed the same .004” out on the end of the taper.

So I went back and assembled the chuck, taking special care to make sure the split right and gear teeth mated without moving the jaws in any direction.

Then, I chucked up a rod from a shock absorber. The rod is hardened, ground and very tight tolerances. I indicated it on v-blocks and got zero runout.

Next, I indicated it and this was the resukts:



Thats right about 0.0016“. pretty good, but its right up against the jaws.

at the bottom of the rod:


Thats about 0.010”.

So yeah, pretty sure the jaws are worn.

Kits are pretty hard to find it seems and the only ones I’ve run across are asking very dear prices.

I might see about trying to true the jaws up a bit more with some of the grinding methods I’ve seen about the ‘net.

It’s “only” on a drill press, but I’d like to get it running as true as I can. Bad enough some drill bits “wobble around” on thier own, last thing I want to do is introduce 0.010 before the drill is even chucked up.

Any input on how I should proceed?

Cheers

 

[darkzero]

I’ve had it apart a couple times now, chasing the runout.

I assume this means you've tried moving the jaws to the next holes & checking runout again? With all the many 14Ns I have rebuilt that's what I did, sucks having to disassemble, reassemble, measure, then repeat but sometimes you get lucky, sometimes you don't.

I see you have an older Hartford USA. On some of them the jaw holes on the body are marked 1, 2, 3 or marked with 1 line, 2 lines, & 3 lines. If you do have the marks put the jaws in the holes they are marked for to start, measure, then clock them to the next jaw hole if the results are not good.

Aside from the jaws I run a round stone in the jaw holes lightly just to be sure there aren't any burrs. Be sure to check the JT taper in the chuck body. I've come across some with burrs at the deep end of the taper. Some arbors don't reach down that far but if yours does then you'll want to check that. I also like to run all the parts over a demagnatizer before final assembly but that won't do anything to improve runout.

When all that doesn't give you good results, then I swap out jaw sets. In my case I had multiple chucks on hand. Sometimes swapping jaw sets from chucks to chucks made great improvements. A couple of times, even swapping in new replacement jaws didn't help. I kept the better ones for use, kept a spare, & sold the rest.

Sounds like maybe it's your jaws that are worn but don't take my word for it, I know new replacements don't come around cheap anymore. Maybe someone else have some more suggestions. Have you tried tightening the key at all 3 holes to see if that improves any?

(This reminds me, I have a 18N I need to refurbish but I don't have extras for it, hope I get lucky)

 

[mmcmdl]

I was just going to post to check out Will's ( @darkzero ) posts on rebuilding these chucks . He beat me to it . I know he has great luck with them .

 

[pontiac428]

Well, it's a Jacobs. About as common as a Big Mac when you go looking. I've never been a fan, and I've even got one or two good ones in the pile. I so much prefer a good keyless. Albrechts are fabulous, and even the good china copies can be pretty decent. I've got a Shars R8 integral shaft chuck that is a treat to use, and you know how I feel about tools that come off the boat packed in VCI paper and soy sauce.

I know, that's not helping you get it fixed. If that's your runout (yuck!), have you measured deflection? How much can you really do beyond cleaning in the home shop? I'm sure you can pick up some NOS replacement jaws, but if there's wear throughout, it might be time to start using it as a shift knob on the old pickup. At least that way, there's plenty of miles left in it.

 

[great white]

I assume this means you've tried moving the jaws to the next holes & checking runout again? With all the many 14Ns I have rebuilt that's what I did, sucks having to disassemble, reassemble, measure, then repeat but sometimes you get lucky, sometimes you don't.

I see you have an older Hartford USA. On some of them the jaw holes on the body are marked 1, 2, 3 or marked with 1 line, 2 lines, & 3 lines. If you do have the marks put the jaws in the holes they are marked for to start, measure, then clock them to the next jaw hole if the results are not good.

Aside from the jaws I run a round stone in the jaw holes lightly just to be sure there aren't any burrs. Be sure to check the JT taper in the chuck body. I've come across some with burrs at the deep end of the taper. Some arbors don't reach down that far but if yours does then you'll want to check that. I also like to run all the parts over a demagnatizer before final assembly but that won't do anything to improve runout.

When all that doesn't give you good results, then I swap out jaw sets. In my case I had multiple chucks on hand. Sometimes swapping jaw sets from chucks to chucks made great improvements. A couple of times, even swapping in new replacement jaws didn't help. I kept the better ones for use, kept a spare, & sold the rest.

Sounds like maybe it's your jaws that are worn but don't take my word for it, I know new replacements don't come around cheap anymore. Maybe someone else have some more suggestions. Have you tried tightening the key at all 3 holes to see if that improves any?

(This reminds me, I have a 18N I need to refurbish but I don't have extras for it, hope I get lucky)

Hmmm, my chuck body is numbered, but I haven't tried swapping them into the “wrong” slots. Worth a try, not much I can damage at this point anyways…

 

[great white]

So I took the 16n apart and shifted the jaws over one spot (ie: #1 in #2 spot and so forth). Then put it back together.

mt pin into the chuck at my alignment mark, mt into the drill spindle at my alignment mark (previously measured to minimize runouts).

first chuck up and measurement came to just a shade under 0.001!

Well I was impressed, but also knew that that was too good to be true.

so I took the rod out of the chuck, gave it a little turn and re-chucked it.

This time I get 0.006 thou.

try a third time and get 0.0035 thou.

each successive try hovers around the 0.002 to 0.004 mark. Each time removing and rechucking the shock rod.

why the big variance between the first two measurements? Dunno, maybe it needed to be tightened down a couple times to get everything seated (or maybe normalized or aligned would be better terms).

I’m going to call that good enough for a drill press that typically deals with bits in the 1/4“ and up range.

Superchuck awaaayy!!!!!

 

[sdelivery]

If the Jacob's arbor has run out it will only be magnified by adding the chuck to the Jacob's arbor........

 

[great white]

If the Jacob's arbor has run out it will only be magnified by adding the chuck to the Jacob's arbor........

Umm, guess you missed the part where I measured the Jt in the chuck and the arbor itself when installed in the drill press…

 

[sdelivery]

Might have let me reread....
This would be the first time I was wrong.....in the last five minutes. lo

 

[sdelivery]

Five tenths! Oops my misread.
Put a dowel pin in the chuck jaws and put it in dowel pin in a precision spindle and indicate the Jacob's arbor bore....I bet you will see or indicate The "bad spot" if not use a black magic marker on the arbor to leave a mark in the bore