Jacobs chuck arbor removal - wedges?
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  1. #1
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    Feb 2004
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    Jacobs chuck arbor removal - wedges?

    I bought a couple of Jacobs Super Chuck N18s (1/8-3/4) that came with arbors. One MT3, one MT5 (big SOB!). These chucks always have JT4 tapers in the back for fitting the arbors. Now, I've pulled arbors before including a JT3 and JT33 recently, and they can be stubborn, but never dealt with a JT4 before. ARRGHHHH!!! I’m beat!

    First off, I tried to order wedges. Too, bad… There are no wedges for JT4! They have them for JT1, JT2, JT3, JT6, and JT33, but nothing for JT4 listed anywhere. Hmm…

    Go to Jacobs site and look around. According to their PDF, one option for removing the chucks is to drill a hole down the center of the body and press it out. Ok, try that. Drilled a hole with magnetic bit to control chips and use a 1/4 Snap-On pin punch to pop it out. Yeah, right. Bent my punch even with careful positioning and adjusting.

    Hmm, too long and spindly maybe, so grab an old foobar center punch and turn it down on my lathe to make a removal tool that is only just long enough to clear the jaws by 1/4". The main bar is 0.300 and drilled the hole out to 5/16 for a easy fit. Near the top is a 0.250 area that is turned to 0.350 diameter to act as a bearing surface so the chuck jaws can help hold it straight. Put a little oil on the bearing surface, and put it in the press. Carefully line it up to minimize side load and start pushing. Seemed to be working, then went “ughh”. Pulled it out and it had buckled about 1/2" from the bottom. I thought the punch would be hard enough, but I guess I need to reharden it, but have not access to a suitable furnace or even make-shift with O/A furnace.

    Oh, and they have been soaking in penetrant for 2 days, though there is no evidence on the arbor or chuck that would indicate that there is a rust problem. The chucks and arbors look good…

    Anyone else got any ideas? I’m stumped…
    Last edited by baddog; 04-01-2006 at 12:17 AM.

  2. #2
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    The few I've needed to deal with the bottom of the chuck was already drilled for the punch. Impact, as in a good whack with a heavy hammer, knocked it right out.

    Hopefully your existing one isn't one of the permanently mounted chucks.

  3. #3
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    You ever try making your own wedges?

  4. #4
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    Not familiar with the actual dimensions of the JT4, but would it be possible to obtain wedges for the next smaller size and use a hand grinder to ease out the "U" notch a bit to fit your taper? Even an inexpensive hobby type hand grinder should easily handle that task. Once you have wedges that fit, you should be able to persuade the chuck to let go.

    Are you positive the chuck has a taper mount, rather than a thread? I don't actually think it WOULD have a thread, but it's always good to stop and ponder the possibilities before applying a bigger hammer. I've ruined some useful items that way and regretted that I hadn't stopped to think about the possibilities more thoroughly

    Another thought: warm the entire assembly in an oven to just below any possibility of smoking the oil or damaging anything, set the chuck up with the rear adequately supported, then apply dry ice to the shank as someone simultaneously taps rapidly on the end of the shank with a punch through the chuck bore.

    Good luck!

    awright
    Last edited by awright; 04-01-2006 at 04:06 AM.

  5. #5
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    Feb 2006
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    This is what I've done in a few cases when the taper is mated up to tight for normal removal porcedures. Take that hole that you drilled and tap it out for a press screw. Ideally a fine thread screw.

    Run the screw in as tight as you can and then whack it with a hammer. Tighten and whack it again, rinse and repeat. You will likely loose the arbor but those are cheap relatively. In effect you end up with a screw driven arbor press.

    As to the screw do use a good grade 8 screw that is long enough to protrude decently out of the chuck. It is best to have a few on hand. You could try an impact wrench but I'm not sure how that would work. Don't have one myself but sure did think it would be nice to have one time.

    The other possibility and one I haven't tried is to hit the arbor with CO2 extinquisher. the idea being to chill the arbor significantly. The problem here is that the chuck body itself would have to be insulated. Also you have to consider the safety issues and act accordingly.

    Dave

  6. #6
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    Sandy: It’s definitely a JT4, not permanent. You can see the taper on the back, and it has JT4 stamped on the nose.

    76GMC: I thought about it, but I have no tool steel or anything with enough carbon to do that. Also, the MT3 arbor does not have enough groove for a wedge to hold, so it would need the drill-and-pin method. And given the forces they have already laughed at, I don’t think a single shear pin is going to hold enough.

    Awright: JT4 is way bigger than any wedge I have (JT3 and JT33). But, I was pointed to a web site this morning that says you can combine JT3 with JT6 to fit a JT4. Not quite sure how that works, but… And yes, it’s definitely a taper (see above). Like you, I have messed things up by “assuming”, so that’s definitely a good suggestion. Heating/cooling I’m not too keen on. Mainly don’t want to take a chance of ruining the chuck, but it might come to trying that eventually, we’ll see.

    Wizard: I don’t think the screw will work here. The material in that back wall drills very easily, and it’s only about 1/8” thick at the hole, so I don’t think it would hold for any significant pressure. Not to mention I don’t think I could run a tap down there inside the chuck. These chucks are huge. And I don’t have ready access to CO2 (without a messy extinguisher that costs $$ to refill/replace) so that will be on the back-up list.

    Thanks all! I’m off to the shop soon to try all my new insights and see what, if anything will work. I'm still thinking the push pin on the press is the best approach, and the small tool I made was just not big enough. I remembered late last night that I have some 1/2" shock shafts that will make a dandy push tool once I turn the end to 5/16, just long enough to reach past the back wall of the chuck to the arbor face. And that should also work for the MT3 arbor as well as the MT5. I’m also going to try the “hydro press” approach again with heavier oil. Maybe the hydro-multiply of 5/16 against that 1” arbor face along with shock wave will do something more than spray me with the back surge around the pin.

  7. #7
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    Maybe the hydro-multiply of 5/16 against that 1” arbor face along with shock wave will do something more than spray me with the back surge around the pin.
    If nothing else maybe the hydro will force a little lube to penetrate from the back side. Little steps and a lot of time works too. Maybe put it in the press and walk off for awhile. Grass comes up through asphalt that way.

  8. #8
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    Well, you don't know me too well. Let’s just say patience is a virtue that has never been one of my strong suites. But sound advice none the less...

  9. #9
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    Man, they almost beat me, but I got em! No Locktite and no rust at all, I've NEVER seen tapers stuck like these. Sheesh...

    Early on I got the MT5 with a combo of the dowels trick and using my tool made from a shock shaft. I didn't have dowels the right size, so I used long shank 3/8 G8 bolts. Tight as I could get it in the vice and it just laughed. But I put the pin in the front and gave it a whack... Pop! One down...

    Now on to the MT3. Man what a BI@#H! Shock shaft is not nearly as hard as I thought. I put it in the press and fooled around with it. Heat, hammer, add pressure, quick cool arbor, whack the base plate, add more pressure, whack the top plate. Ok, pull it out and try something else. Oops! The pin won't come out! I forgot to turn it undersize after giving up on the high pressure hydro experiment and the pressure was enough to swell it! Man, I like to have never got it out! That was a whole other project of it's own! Anyway, I finally gave up and cut it off, drilled it out and eventually got it. Took several HOURS! First off, I drilled it out on the mill, and couldn't keep MY DRILL CHUCK ON THE **** ARBOR!!! Ever tried to hold a drill chuck rigid enough to do anything with? It's nearly impossible. It kept wanting to wiggle, popping my Rohm 1/2 chuck off it's JT33 arbor several times as I worked my way up to a 1" bit. Then put it on the lathe to bore out and true up the hole which was crooked and off center a bit. Chuck nose taper won't let it fit in my outside jaws, too big to fit in the inside jaws, so I chucked up a piece of that shock shaft that was handy and tightened the chuck onto it. Good enough for this purpose, though not the most rigid setup you might want... Eventually got it bored out by "step boring" since I can't turn an inside taper on my lathe without a taper attachment. Got it down almost as thin as tin foil, maybe 0.015 (yeah, I know) and it STILL was a PIA to peel out. Now I have it out, but the taper is scarred up as well as some scars on the outside of the chuck from all the various attempts today. I'll hit it with paper rolls tomorrow, should be ok I think...

    I’m beat. Took half a day to get out 2 tapers, and most of it on just the MT3!!!

    Thanks for all the help!

  10. #10
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    Sorry, I have to chuckle a little reading about the affair. It's typical of something that's supposed to be a ho-hum routine 'change the chuck' and ends up being the project from h**l. Red blood shot eyes, can't sleep at night, bent or broke every tool in the shop. Some body says "chuck" and you get a twitch in your left eye!!!

    Glad you got it. You hung in there. Good thinking, good work.

  11. #11
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    Have you ever seen the movie "money pit" with tom hanks...not a great movie, but at the end of all the crap that happens, he has this scene where the bathtub falls through the floor and he starts to laugh...like a mad man. Sounds like baddog, was about to this point with this chuck from HADES.
    Smithboy...
    if it ain't broke, you ain't tryin'.

  12. #12
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    LOL! Both posts are dead on!

  13. #13
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    Oh, just realized it probably isn't clear when I said:
    I finally gave up and cut it off, drilled it out and eventually got it.
    I was talking about the arbor, not the pin that collapsed/deformed, swelling into the hole. I didn't even go into the hour or so it took to get the pin out... Muah hahaha, ha ha ha ha… {laughing maniacally with eye twitching}

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