Difficult Machine Bolts On Lathe Chuck

Martin Angus

Martin Angus

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Dec 20, 2012
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Hi all,
I have been tearing down an old cushman 12" lathe chuck and 6 bolts don't want to budge (even with my trusty impact gun). They appear to go thru with a funky looking back - that may be a nut? Any ideas? What type of driver would I use? I'm being gentle and want to avoid the "bigger hammer" method of disassembly. Here's a pic.6 bolts on cushman.jpg
 
First I would try an extension on the hex wrench. If that fails, then I would use a flat nose punch that fits the OD of the head of the screw, and smack the punch with a hammer, hard. Then try the hex wrench and extension again. Normally this will break things loose.

Worst case, drill the heads off of the screws.
 
impact gun may just not have enough power, cheater bar as long as it takes
or try to just loosen one of the back nuts, as nuts they will be, with a puch and a hammer
if that works grind yourself a tool from a screwdriver
 
They could be lock nuts.
Maybe the adapter is threaded also, then the lock nuts were put on and tightened.

Make a tool and try to remove them.

Some gent may have put in loctite: A little heat will break the bond.

I do not see much use for the complicated bolting, must have been deigned by a "Text Book Engineer".

Unless you are using a 1/2" stout impact with 120 pounds of continuous air you are spitting in the wind.

Or, horrors, could be left hand threads!!! You should be able to look into the slot on the nuts and see which way the helix is sloped.
 
Without previous knowledge, I'd vote for lock nuts. If you can see the direction of the thread,that would be a bonus. It's possible they're left handed, some automobile wheel nuts were left handed in the mistaken belief that they would unscrew under torque.
 
That was a "A-1" Mounting on that chuck originally. IT was changed to a "D-1" mount. They filled the holes with SHCS and nuts. More than likely loctite applied and super tighten for no reason what so ever.

Go in with a carbide drill on the nut side and drill out near the SHCS threads. Then apply Allen wrench with some torque and twist off the SHCS. Remove nut and twisted off SHCS and you got it.
 
They look like some kind of jam/lock nut, or just a nut. And there design was so they are flush mount with a minimal outside dimension. That’s why they look like that. I would first make a tool that nicely fits the slot and try that. Noting direction of thread…Good Luck, Dave.
 
Martin,

Can you supply the number that is stamped on the metal label on the face of the chuck? I have a older Cushman Chuck catalog/parts book that may show how that's put together I'll be able to post.

Ken
 
I agree,, those are lock nuts on the back, and will be PITA to remove...
I think you'll need to make up a suitable driver to loosen them. piece of decent heat-treatable steel tube that *just* fits over the threads, turned to the OD of the nuts, then hollow-ground to get a snug-fitting "screwdriver" tip - any angle left on the tip and they'll just cam out and/or wreck the slots... Harden and temper once you have a good fit in the slots, polish up and away you go - in situations like that I'd use Mechanical Assistance to keep the driver in the slot, e.g. clamp the whole lot up (chuck, driver in compression etc.) in the vice so it can't slip out and leave the nuts boroughly thuggered - good luck!

Dave H. (the other one)
 
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