Problem removing arbor on Criterion boring head

4cyclic

Registered
Registered
Joined
Sep 8, 2016
Messages
35
I just bought a used Criterion 203 boring head for the 949TS. It came with a 1 in straight shank, but I can't use it, so bought a Criterion R8 1 1/2-18 shank.
Problem I can't seem to be able to undo the 1 in shank. Tried to hold the shank tight in lathe chuck and using moderate force on an attached 3/4in boring bar, but no luck, any clever ideas ?

John
IMG_0150.jpg
 
Grind some flats on the 1" shank..... And clamp the boring head in a vise by the grey end....
 
You could grind the flats and hold the head in a vise that has soft jaws or just use a pipe wrench if you don't care to save the staright shank.
Those straight shanks are over $40 retail so would be nice if you could keep it in good condition.
You could try taking the sliding part out of the head and apply heat inline to the threaded portion. Hopefully the boring head expands a little quicker than the shank threads.
 
Look really carefully to see if there is a set screw or pin installed from the side of the head into or against the shank. That is common, because boring heads are often run in reverse, and we don't want them to unscrew when cutting. Consider adding such a feature for the new shank if there is not one already. There are often flat spots on the shank as well for a set screw to push against, another way to stop unwanted unthreading.
 
It may have had threadlocker applied to the threads. I think the judicious use of heat may be helpful
 
You could grind the flats and hold the head in a vise that has soft jaws or just use a pipe wrench if you don't care to save the staright shank.
Those straight shanks are over $40 retail so would be nice if you could keep it in good condition.
You could try taking the sliding part out of the head and apply heat inline to the threaded portion. Hopefully the boring head expands a little quicker than the shank threads.

Yes, thanks ddickey and Cooter, that's my last resort method. I would prefer saving the shank if possible, but I also thinking about putting the part in the oven at 275 deg F for 20 minutes, minus the grey top. Maybe a Loctite type compound (242 or 262) was used.

John
 
Look really carefully to see if there is a set screw or pin installed from the side of the head into or against the shank. That is common, because boring heads are often run in reverse, and we don't want them to unscrew when cutting. Consider adding such a feature for the new shank if there is not one already. There are often flat spots on the shank as well for a set screw to push against, another way to stop unwanted unthreading.

I checked, and took it apart. No pins or setscrews. This is good idea anyway. Certainly not good if it unthreads while reversing !!
 
A last resort that can be dangerous in the sense that you could break a parting tool. wink wink.
Chuck up the boring head in a four jaw. Use aluminum or brass shims to protect the head and do not reefe down on it just snug. Invert your parting tool and run the lathe in reverse as you begin to part off the shank. It should start to unscrew and as soon as it does you must immediately reverse the cross slide. I was a little to late in doing that and broke my blade but I got the darn shank off. Sort of a red neck way of doing it but it did work.
 
Back
Top