Criterion Boring Head, Shank Removal. Meet my new Adversary.

[tq60]

I would think something turning clockwise cutting would have RH threads.

Have you went to the manufacturer and either located the data sheet or just call them to ask how they are assembled?

Maybe a locking device or something other stupid thing.

The amount of force you have applied is substantial so a lock may e present.

Since you still have enough left to dial in, set it to zero and wrap a few layers of soda can around it and place it in your lathe holding by head.

Use 4 jaw and dial it in true center.

Carefully cut it off then drill it out.

The center should not be as hard as the outside.

Drill out enough to allow boring bar use then carbide boring bar.

If you are lucky it may spin out once you get the register off but it it has thread locker you will need to bore out until you remove most of the center.

Or...

Impact gun, impact works much better than brute force.

Either grind to fit a socket or weld on a big nut.

Sandwich some 2x6 in a vise and with hole saw cut out a slug just smaller than head.

Now place them around head and clamp tight in vice.

Impact gun to work, our HF unit does 600 ft pound in reverse, used it to remove 5/8 building bolts be breaking them, it may bust it loose.

Sent from my SM-G781V using Tapatalk

 

[GL]

Ah yes, side projects. The bane of the 10 minute fix. As I recall, Criterion arbors are RH fine thread, so the minor diameter would be bigger as you bore things out looking for them. You would think heat to kill Loctite would be your friend. To change the game a little, if you part off the R8 shank, can you mill wrench flats on the arbor flange to get some more gronk on what’s left? Without chewing up the body of the head.

 

[benmychree]

I would not use heat, you would draw the temper of the body, I would machine off the flange as others suggest, and try to screw the shank out, if that did not work, then drill and bore the thread ID and pick out the remaining thread coil.

 

[pontiac428]

The heat input from the welder didn't seem to do it, but those welds all broke at the heat affected zone/fusion zone, which tells me it isn't the idea that didn't work out as much as it was the setup. I'm only suggesting 300F or so to soften any caca in the threads, which shouldn't hurt the temper. Heating (mildly) and shocking with a dunk in water has been the most successful way to break stuck threads loose in my experience.

 

[AZCCJ]

Thanks for everyone's advice. Today I had a chance to remove the shank from the boring head. I first used my small Dewalt bandsaw and cut the shank off from where I had it welded to a trailer hitch. I don't know what this Criterion shank was made of but the bandsaw went right through it as if it was made of Styrofoam. I then made some thin copper shields to go onto my 4 jaw chuck's jaws to prevent damaging the head. I then mounted the head in the 4 jaw chuck and centered it to less than .0005". After turning down the shank's flange that rests up against the head, to about .010" thick and turning down the shank a bit, I took a set of channel locks and easily unscrewed the shank from the boring head using no more than 10 foot pounds of force. There was no Loctite on the threads and all the threads had liquid oil still on them from when they installed the shank, I don't know how many years ago. The threads in the boring head are in perfect condition and the new shank screwed right on.

I have never seen anything like this in all my mechanical doings. When I used my tractor to try and break it free, I would guess that 500+ foot pounds of force were being applied to the shank and it wouldn't budge. Then just simply removing that flange allowed the shank to easily unscrew. Go figure. Once again thanks for everyone's advice.

 

[mattthemuppet2]

nice job! Now you have a stub arbor too My guess as to what happened is that the old arbor had self tightened through use to the point where the flange pushing on the threads had slightly stretch the arbor threads so that they were completely jammed up (like torqueing an engine head bolt). By reducing the flange thickness to the point where it couldn't exert that force, you allowed the threads to relax back into their normal state and unscrew. Either way, glad you got it off!

 

[Charles scozzari]

nice job! Now you have a stub arbor too My guess as to what happened is that the old arbor had self tightened through use to the point where the flange pushing on the threads had slightly stretch the arbor threads so that they were completely jammed up (like torqueing an engine head bolt). By reducing the flange thickness to the point where it couldn't exert that force, you allowed the threads to relax back into their normal state and unscrew. Either way, glad you got it off!

I was able to cut the off the Bison stub also using my Milwaukee portable. I then disassembled the boring head and it's in my lathe chuck. I will follow up with my progress. Glad you were able to remove you arbor.