View Full Version : Jacobs Drill Chuck/Arbor Prob

06-02-2003, 12:20 PM
I have a 1/2 jacobs chuck that I've been using for 2 or 3 years with no problem.
Whilst drilling in my mill the drill chuck came off the #2JT taper of the .5" straight shank arbor. (This happened as I was lifting the turning drill out to clear the chips.) Both mating surfaces looked good as new, so I cleaned both w/acetone, blew dry, and remounted, gave it a few light taps to seat it, and tried it again. ...Chuck immediately came off again. Repeated the process, with same results. Son-in-law showed up about that time, so I asked him about using Loctite, which he discouraged. He suggested I twist the arbor as I seated it in the chuck. So I recleaned/dried, and then seated with a twisting motion, then tapped. Came off again. So this time I pulled out the ol' Loctite and dosed the taper with a film of that, inserted it with a twist, waited a few hours, and tried it. So far it's held.
But I'm wondering if I'm missing something. Anyone have any thoughts to offer?

(1) Prior to the first dismount, the drill (3/8") had slipped in the chuck as I was opening up a smaller hole (about 5/16 or 1/4), which required retightening. But the drill was still cutting just prior to lifting to clear chips.
(2) Material was aluminum.
(3) On those unsuccessful attempts, the chuck would come off immediately just as the drill would enter the hole, with no great force.

06-02-2003, 12:38 PM
lynnl, get out your biggest arc welder, crank voltage up to at least 200 amps and weld together. If that doesn't work, try a bead of silicone. JUST KIDDING!

If it wasn't loctited together, I would say to paint your arbor with prussian blue or magic marker, slide together and twist to see if you are getting good/full contact. It sounds like your jacobs tapers don't match up very well. But you say it has worked for awhile with no problems. Are you sure you seated them together tightly enough?

06-02-2003, 02:08 PM
Well, considering that they didn't stay together, I guess I'd have to say I did NOT seat them tightly enough. http://bbs.homeshopmachinist.net//biggrin.gif But after installing I was tapping the arbor end on the table of my bench vise (upside down)....not exactly baby taps. Yeah, I should've thought of the Prussian Blue before using the Loctite. If it comes apart again I'll do that. Both chuck and arbor are Jacobs brand. Kinda disappointing to think THEY can't make the tapers match correctly.

06-02-2003, 05:51 PM
I've had a chuck taper and spindle locktited for a couple years. Blue locktite, I wanna be ABLE to get it out.

Has worked fine. Pulled it once and put it back after cleaning it off.

MT2 socket is kinda crummy, shows machining marks (not spin marks, it has a tang slot). And the machine is an old no-name import.

I woudn't be ashamed of it, locktite and go on.

06-02-2003, 06:14 PM
If you press it together enough to truly seat the taper, you're going to squeeze out all the Loctite anyway, so I don't see how it's going to help you any.
I guess if the fit is bad, there might be enough gap to make it worthwhile.

06-02-2003, 07:09 PM

If all else fails, drill through the bottom of the chuck and tap into the arbor. Attach chuck with a flat head socket cap screw. This is the way the they kept the chucks on the reversible electric hand drills.

06-02-2003, 09:47 PM
Lynn: I have installed set screws (on an angle) to hole morse tapers in. I have done this on three machines. selected a spot on the machines so the screw was same place on each machine. then ground a flat on tapers so the screws set same place on ech taper.

I also used a hot air gun to heat the socket (little warmer than boiling water at the end-it sizzled when i touched it with water), shoved a cold taper into the thing and let it cool. too much trouble to take out, but i think it would have been even harder to break locktite.

06-03-2003, 10:06 AM
I'd forgotten it, but that chuck already has a hole in the bottom. I'd had to drill thru and punch out the original taper it had when I got it. (originally was grossly out of true) That original arbor had been loctited in, cause even after drilling, I couldn't punch it out til I baked it in the oven for a while.
If it comes out again I'll put the arbor in freezer and heat the chuck, prior to inserting. And then if it fails I'll tap for a screw into the arbor taper end. (Do you suppose that arbor taper is hardened?)

If I ever get my toolpost grinder made I may try making an arbor and grinding it true to the chuck. I have two Jacobs 1/2" chucks and the TIR on both leaves much to be desired.

06-04-2003, 03:35 PM
lynn: If yu can, drill and tap some where you can reach, insert a screw so you can "jack" those shrunk parts apart. I put a 1/4 20 screw in the tip of morse taper socket tang. Tighthend up on the screw, frapped it with a hammer and anvil and it popped out.
Gotta think ahead when I repair something- it WILL have to come apart again. Too often i have brazed or welded things together to get a job done and worked a long time to get it apart so i could fix it again http://bbs.homeshopmachinist.net//smile.gif


06-05-2003, 12:32 AM
The heated chuck, and freezing arbor trick works too well sometimes. A hydraulic press is usually needed to get it off again. Better than Loctite! http://bbs.homeshopmachinist.net//biggrin.gif

Paul Gauthier
06-05-2003, 07:44 AM
The arbor taper is mostly not hardened>

Paul G.