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View Full Version : Removal of Jacobs 33JT from a No. 2 MT Arbor



hammerfest
06-12-2010, 08:39 PM
Gents--before I turn this job into a mess, might I solicit your expertise and ask how to remove a Jacobs Chuck with a 33JT Taper from a No 2 MT arbor. The arbor is a short guy and there is just no good way to hold it to tap the chuck off. I have no use for the arbor and had contemplated welding on a bar so as to have something to grip.

Any suggestions? In advance many thanks!

Jim Shaper
06-12-2010, 08:46 PM
Drill a 3/16 hole in the center of the chuck body and drive it off from within using a drift.

jdunmyer
06-12-2010, 08:55 PM
The "proper" way to remove an arbor is with wedges: http://www.use-enco.com/CGI/INSRIT?PMAKA=240-2666&PMPXNO=4839882&PARTPG=INLMK32

Note that there's 4 sizes, I'm not sure which one you need.

I once had an arbor that I had to bore out to remove, that's another method.

hammerfest
06-12-2010, 09:02 PM
Jim--thanks good idea, I'll give it a shot.

jdunmyer--thanks for the idea about the wedges they would work if I had something to wedge against, like a flange on a drill press.

Arthur.Marks
06-12-2010, 09:29 PM
In such cases, I have two options:
1) if the arbor has a tang, clamp it in your bench vise real good. Take a soft-mallet and give the back of the chuck body a whack. Done.
2) if there is no tang, or you just are worried the above technique will damage the JT33 taper seat... I take such occasions to completely disassemble my chuck and clean it. Some chucks have a screw that advances the jaws and once the chuck is disassembled, you can access the back of the mounting arbor. If not, once disassembled, it usually is real easy to devise a way to safely whack the thing off :)

Jim Shaper
06-12-2010, 09:30 PM
Jacobs has the drift method posted on their website. Wedges are iffy on some really stuck chucks (I've had them split rather than popping the chuck loose), and of course you rarely need them so it's an added tooling expense. The hole down the middle doesn't effect the strength of the chuck body, so there's really no reason not to use that method.

MichaelP
06-12-2010, 10:55 PM
Some chucks have the center holes predrilled, so it's worth checking prior to drilling.

JCHannum
06-12-2010, 11:07 PM
The wedges are the first line of defense. Drilling the body of the chuck and tapping for a jack screw to remove the arbor is the second. The wedges are iffy, and if you don't have them or there is no shoulder to use them against, you can skip the first step.

You might be able to tap the chuck off with a drift through a hole in the body of the chuck, but a fine thread jack screw works better. There is a cavity between the back of the chuck and the arbor so the tap will clear without binding on the arbor.

BadDog
06-12-2010, 11:43 PM
I've used wedges to remove chucks, and I've ruined wedges trying. I've drilled holes and used existing holes through the chuck, sometimes it works, sometimes not. I've even tried the "hydraulic" method, but had little luck if the others don't work. For one particularly troublesome 18N chuck, I was finally forced to resort to drilling and then carefully boring to remove an arbor too large for my lathe. Of course, now I have a lathe that it would have fit...

Bob Ford
06-13-2010, 12:09 AM
Chuck the jacobs in the lathe and turn the arbor and thread. Put a spacer and nut on, tighten nut and if the parts do not separate hit adapter with hammer. Then re-tighten nut.

Bob

MichaelP
06-13-2010, 12:44 AM
Funny that I had the same problem as BadDog with my 18N, went through all methods described in this thread plus more and finished up boring the arbor out. Nothing else worked.

fishfrnzy
06-13-2010, 01:04 AM
Bob, that one is clever. I like it and may have to use it soon on one of mine.

Black_Moons
06-13-2010, 01:15 AM
33JT tapers like to rust up and lock hard, Sure your not better off just buying another chuck and keeping it on the adapater? :)

Arthur.Marks
06-13-2010, 11:27 AM
One other issue, actually one I encountered last night:
Crazy folk sometimes put loctite on the arbor shaft :eek:

Evan
06-13-2010, 01:04 PM
Stick the chuck in water not quite up to the arbor and heat the arbor with a torch, the faster the better. Oxy/acetylene is best. The differential expansion will break any rust and will also destroy any loctite bond. Will likely work but not guaranteed.

Peter.
06-13-2010, 02:08 PM
I had a chuck that is fitted to the arbor by having a countersunk screw holding it through the centre hole.

Boucher
06-13-2010, 03:58 PM
I had a similar problem and was reluctant to drill the center of the chuck. When I finally did I was amazed how easily it drilled. There is some space betwen the back of the chuck and the arbor so it is obvious when you have drilled thru the chuck. Put a little Kroil in the hole and tapped it with a punch and hammer. Very easy and quick. I had tried wedges but couldn't get it to budge. The hole in the center sure worked for me.

rohart
06-13-2010, 08:05 PM
Even if there's already a hole through the back of the chuck, it may be too small to be useful.

Open it out for a nice whack with a good punch. Never failed me yet.

The last two I did were getting a super ball bearing 14N off a 3JT and an 18N off a 4JT.