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Punkinhead
04-13-2010, 09:30 AM
A friend of mine wants to remove the R8 shank from his Criterion boring head to exchange it for a straight shank. It's on pretty tight. What's the best way to unthread it without boogering up the head or shank? He can cobble together a spanner to use on the head, but what's a good way to tightly hold the R8 shank?

JCHannum
04-13-2010, 10:43 AM
A friend of mine wants to remove the R8 shank from his Criterion boring head to exchange it for a straight shank. It's on pretty tight. What's the best way to unthread it without boogering up the head or shank? He can cobble together a spanner to use on the head, but what's a good way to tightly hold the R8 shank?

The milling machine?

Glacern
04-13-2010, 10:48 AM
Aluminum soft jaws in a vise will do the trick without marring the shank.

If it's a DBL boring head, an aluminum bar through the cross hole can be used as a lever.

David Powell
04-13-2010, 11:01 AM
One day I was using my boring head on a job, but for some reason, now long forgotten,was running the mill in reverse. Eventually the inevitable happened and the arbor unscrewed and the head fell off, fortunately without wrecking anything. I has a customer waiting so I screwed it back on with a good dollop of Loctite bearing fit on the threads, had a cuppa and went and finished the job. That boring head is in the rack as I type, but maybe others have been so treated elsewhere. At least I didn.t weld it. Regards David Powell.

Punkinhead
04-13-2010, 11:09 AM
I should have mentioned that the reason for changing shanks is that he got rid of his old Bridgeport and his new mill isn't R8. We could use mine, but I wouldn't think the brake would hold the spindle tight enough to get the shank loose.


One day I was using my boring head on a job, but for some reason, now long forgotten,was running the mill in reverse. Eventually the inevitable happened and the arbor unscrewed and the head fell off,
I'll offer to bore some holes in reverse for him, but I doubt he'll go for it. :D

I talked to him last night so by now he's probably used Glacern's suggestion of soft jaws and got it off himself and my question is a moot point.

Black_Moons
04-13-2010, 11:19 AM
Hmm, Well, Maybe if you inserted a bolt into the R8 shank and used a jamnut you could tighten it enough to be able to use the bolt to keep the shank steady?

other thoughs would be something like a pipe vise + rubber innertube or somesuch to prevent maring.

Drilling a hole for a pin wrench could also do.. :P

3t-
04-13-2010, 01:38 PM
drill a block of hardwood, hole the size of the shank. split the piece of wood across the diameter of the hole. clamp the shank in the wood in a big vise. kind of a poor mans barrel vise.

Vern2
04-13-2010, 01:51 PM
Buy an adapter for his R8 milling tools. Like MT1 ... 5 Taper to R8.

Forrest Addy
04-13-2010, 02:32 PM
Put the shank in the R8 Bridgeport (with NO indexng key because you took it out. Right?), put the spindle in back gear. Insert steel rod as a lever in the side hole of boring head, apply brake and loosen the head as with right hand threads. Use the spindle brake (now with geared mechanical advantage) to keep spindle from turning. It won't be that tight.

Black_Moons
04-13-2010, 04:25 PM
forrest makes a good point.
But with a good wack on the bar with an 'adjustment mallot', I bet you don't even need the spindle break, just the momemtium of the motor at rest should be enough to prevent the boring head from rotating on the initial impact.

duckman
04-13-2010, 05:55 PM
It all depends how the shank was installed, when I install mine I clean both threads very good, like licking clean, them put extremely hard to remove lock tite on both threads put the head on about 2 or 3 threads, start the Brpt. at about 1000 rpm then hold the head with a gloved hand, takes about 1 second to slam them together I've never had one come apart even when boring in reverse.
:D

Punkinhead
04-13-2010, 06:53 PM
It all depends how the shank was installed, when I install mine I clean both threads very good, like licking clean, them put extremely hard to remove lock tite on both threads put the head on about 2 or 3 threads, start the Brpt. at about 1000 rpm then hold the head with a gloved hand, takes about 1 second to slam them together I've never had one come apart even when boring in reverse.
:DHere's hoping my buddy didn't buy one of your old boring heads. :D Actually, my interest in this is that I bought a boring head off ebay with a chewed up shank (which came right off) so I don't want my friend to chew up the R8 shank because I want to use it.

TDmaker01
04-13-2010, 08:33 PM
I have found that putting the shanks into the 3 jaw chuck on my little ole' Raglan lathe and engaging the spindle lock (its a geared lock so there is not slip unless the pin shears off) makes a very good pipe\round stock vice, but when you smack, or pull the bar in the cross hole of the head make sure not to bang the bar or your nuckles off the bed ways.