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Problem removing arbor on Criterion boring head

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4cyclic

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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 ?

JohnIMG_0150.jpg
 

Cooter Brown

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Grind some flats on the 1" shank..... And clamp the boring head in a vise by the grey end....
 

ddickey

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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.
 

Bob Korves

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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.
 

seasicksteve

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It may have had threadlocker applied to the threads. I think the judicious use of heat may be helpful
 

4cyclic

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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
 

4cyclic

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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 !!
 

ddickey

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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.
 

4cyclic

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If it worked, it ain't bad !
 

ddickey

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You could probably flip a turning tool upside down and run the lathe in reverse taking some healthy cuts. That would probably be a little safer.
 

mmcmdl

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Why can't you use the straight shank in a 1" endmill holder ?
 

Bob Korves

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Why can't you use the straight shank in a 1" endmill holder ?
You can. If R8, the shank will only go about an inch (edit: 1.2") into the 1" collet before it hits the step. That is no real issue, because all the clamping gets done in the last 1" anyway. Short shanks (1 to 1-1/4" long) make for easy tool changing, and with no down side.
 
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kd4gij

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With the boring head info printed on the shank. There is a good chance it is an integrated shank.
 

JimDawson

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I put shank in the lathe chuck, tightened the gib, stuck a 3/4 x 6 pin in the side hole. Then smacked the pin a couple of times with a hammer, came right loose.
 

ddickey

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If that boring head is a Criterion I don't think they ever made an integrated shank.
 

4cyclic

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The 1 in shank is quite long and would need to be cut to 1 1/2 in long to fit an end mill adapter or a R8 1 in collet. I thought about it, but decided to buy the R8 shank, before trying to undo the 1 in shank, ha !

The R8 1 in collet would be too fragile, I would assume for a 3 in boring head.

I tried to use the 3 jaw chuck and a 9 in long boring bar, whacking it with a dead blow hammer, but the shank was rotating in the jaws.
 

ddickey

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Try my suggestion I bet you get it out.
Max R8 collet is 7/8", no?
 
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Bob Korves

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Try my suggestion I hey you get it out.
Max R8 collet is 7/8", no?
My R8 set goes to 1", but for only 1.2" deep into the collet. All the clamping on a R8 collet is near the nose end.
 
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Bob Korves

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The R8 1 in collet would be too fragile, I would assume for a 3 in boring head.
Not so sure about that, but it might be an issue. The collet is well supported by the spindle in the nose area, not at all beyond that until the drawbar end.
 

4cyclic

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Well got it off finally. Resorted to grinding a flat on each side of the 1" shank and using the vice, but it took careful torch heating to 500 deg f to loosen up the red Loctite. I only heated up the main body, not the moving parts. A good whack with dead blow hammer and it spun around.

Thanks for all the help guys, much appreciated.

John
IMG_0151.jpg
 

JimDawson

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I can't imagine why anyone would locktite that together. I certainly would not.
 

Bob Korves

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I can't imagine why anyone would locktite that together. I certainly would not.
To keep it from unscrewing when turning it in the opposite direction. There are probably better ideas, but is worked for the previous owner...
 

JimDawson

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To keep it from unscrewing when turning it in the opposite direction. There are probably better ideas, but is worked for the previous owner...

I guess if you had to lock it, a set screw on a flat would be a better choice. I don't recall ever having to run a boring head backwards, but I guess you might need to if you were cutting on the OD of something.
 

Bob Korves

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I guess if you had to lock it, a set screw on a flat would be a better choice. I don't recall ever having to run a boring head backwards, but I guess you might need to if you were cutting on the OD of something.
If all, most, or many of your boring bars are right hand...
 
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