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radkins
05-06-2009, 04:28 PM
I was just given (yep GIVEN! :D ) an almost new Jacobs 20N Super drill chuck. I have an arbor with the right 3MTx5JT to mount this thing to my lathe but the problem is there is still a section of an old arbor left inside the chuck, it has been sawed off flush with the back of the chuck and drilled out to about 1" and roughly 1-1/4" deep. I have no idea as to the purpose of doing that but that is what I have right now and I need to get this piece out, any ideas? How would be the best way to normally remove an arbor?

pcarpenter
05-06-2009, 05:10 PM
This has been covered here a few times, but the use of chuck removal wedges sounds like it's out in your case.

The other easiest method...assuming they did not hack the arbor as you described in an failed attempt to get it out is to simply drill in the center of the chuck and drive it out with a punch. This would destroy a keyless chuck because they have "works" in the center, but a standard chuck like that one does not. They are also not hardened in the center. Open the jaws up and you will find and indent you can use to center the bit and drill away. Hopefully that is all it will take.

Congratulations on your "find". I hope it works out for you.

Paul

JCHannum
05-06-2009, 06:14 PM
The wedges are usually successful only about half the time, requiring drilling the body of the chuck for removal. It is a standard method and recommended by Jacobs. When drilling the center of the chuck for arbor removal, drill a tap size. If the arbor cannot be removed with a punch, it can usually be removed by tapping the chuck body and using a bolt to jack it out. I use a fine thread, for a 20N, a 1/2-20 or larger should be used.

Sometimes a chuck will resist even that method. In that case, the only remaining thing is to dismantle the chuck and machine the arbor out in the lathe. Arbors are usually case hardened and can be bored on a taper, leaving a thin shell that can be removed with a chisel.

MTNGUN
05-06-2009, 06:20 PM
Dunno about the Jacobs but the clones (Golden Goose, Accupro) have no metal in the center of the chuck, if that makes any sense.

To remove the arbor stub, set the chuck on your vise jaws, arbor side down, with the jaws opened enough to allow the arbor to fall out.

With the chuck jaws open, take a punch, stick into the chuck, and give the arbor a light tap. It should fall out.

What I am trying to say is that, when you stick the punch into the chuck, it should come to rest on the arbor. There is no metal separating the arbor from the chuck opening. At least, that's how the ball bearing clones work.

Bruce Griffing
05-06-2009, 06:21 PM
If there is enough meat at the bottom of the arbor, you can tap it as JC suggests, but instead of jacking it out - use a bolt and a short length of pipe to make a puller. This has the advantage of distributing the force around the back of the chuck rather than concentrating it at a single point. Either will probably work.

JCHannum
05-06-2009, 08:16 PM
It is the chuck body I was referring to tapping, not the arbor although that might be feasible. The end of the arbor might prove too hard to drill & tap. There is enough meat in the chuck to support threading, but fine threads are advised.

BadDog
05-06-2009, 08:16 PM
I had an 18N somewhat like that. Wedges wouldn't touch it, punches wouldn't budge it, I even made a press pin and put it in my 20T press; it mushroomed the pin! I was scared to use a hardened pin with as much pressure as it took to mushroom the soft steel pin (thought I never would get it out!!!).

In the end, I clamped the chuck onto a 3/4" pin (IIRC), and put it in the lathe. Cut off the arbor, drilled it, then step drilled to remove most of the JT4, and finally used the compound to turn out most of the remains. Even when it was paper thin, I thought I would never get it all out.

In the end, I was wishing I had bought a new one, but at last, I prevailed. Now it is mounted on a 3MT for my big 20" VSG drill press, or used with a MT4 sleeve in my lathe...

Bruce Griffing
05-06-2009, 08:57 PM
My experience is that the centers of arbors are not usually hard. I have removed several by the drill, tap and pull routine I suggested above.

radkins
05-06-2009, 11:43 PM
OK, I just got this thing out. I used a 3/8" bit and drilled through the base of the chuck from inside as suggested (at least that is the way I thought it was suggested) and then placed a 5" long 3/8" bolt through the hole onto the end of the arbor. I then snugged the jaws of the chuck around the bolt to hold it in alignment and smacked the head with a hammer, after about 4 rather hard blows it popped out. :)

Thanks everyone for the suggestions. I have to admit I hesitated a couple of days before making this post because I feared it was a rather dumb question but from the replies it seems this is normally a rather difficult task to accomplish!