Removing 3/4” shank from 7/8”-20 boring head

[erikmannie]

I have a Criterion S-1-1/2” boring head that I bought used on eBay. It came with a 3/4” straight shank attached.

I tried & failed to remove the shank. The shank has no flats anywhere on it. I wonder if the previous owner used some Loctite or similar.

Does anybody know a way how I can get this shank off? How does one securely apply torque to a circular object?

I know for a fact that it is a right hand thread.

 

[erikmannie]

As you can see, the shank has seen better days. It is the boring head that I want to keep in good shape.

In other words, I would consider machining on the shank if that’s what I need to do.

I have 5C collet blocks. Do I need to machine a hex on there?

Is it a stupid idea to drill a cross hole in the shank & then press in a long lever of sufficient hardness?

I feel like a long, securely attached lever will be the key.

 

[darkzero]

The straight shank I removed had a weldon flat, I wanted to save the arbor so I did this.

If you're not concerned about saving the arbor then it's much easier being a square head Criterion. Machine 2 flats on it to grab it with a wrench. Or if you want, machine a hex, then you can use a socket & a breaker bar or hit with an impact gun.

 

[francist]

Maybe if you knew someone who welded they could fix a bar at right angles to the end of that shank for lots of leverage and no flats to round off. You’d have to know a weldor though…

 

[erikmannie]

Thank you for all of the helpful responses. I can see that the boring head being square makes it easier to hold in a vise. It had not occurred to me to hold it in a milling machine vise.

I have an 8” Kurt vise, but I sure would not want to cause harm to that vise or the table on the milling machine.

I have broken a Chinese 4” bench vise using a cheater bar. That set me back over $100 to replace the bench vise.

I love this little boring head, & I don’t think that I would have the money to replace it were I to deform it under torsion while it is clamped in a vise.

It seems like I would have a better chance of success if the leverage were applied near the threads, as this would minimize any twisting in the 3/4” shank. This plan has me machining a hex on the shank near to the threads, & then using a wrench with a cheater bar (if necessary).

If this fails, I would feel very comfortable drilling & boring out the shank. I would hold the square head in a 4J (with soft jaws!) & just make sure to stop short of the crests of the threads on the boring head.

Having said all the above, I will likely stick weld a long piece of 3/4” round or hex bar to the end of the shank. Talk about a bend test, right?

Do we expect that the shank is medium carbon steel (such as 1045)? Does anybody see any reason not to use a 6010 electrode? The only other choice is 7018.

Would you guys choose round or hex bar? I will probably make it very long, & increase leverage (by moving my hands farther apart) as needed.

I will soak the threads for a long time in an appropriate thread loosening compound, this after the welding job. If you think about it, this has the whole head soaking in a vessel of thread loosening compound for about 7 days. I wonder if that might present a problem for the boring head; Heck, maybe it would provide excellent lubrication for the head!

We note that the soft jaws (which will be aluminum) for the bench vise & 4J (copper soft jaws if I resort to drilling & boring) need to have some areas machined out because there are 3 set screws that need to be protected. I would be afraid to remove the screws because I know there are ball bearings under the set screws, & Murphy’s Law has me losing exactly one of these ball bearings.

All of this trouble to “upgrade” to a quality R8 shank.

 

[Ed ke6bnl]

Might be a good chance that the bar is lock tite threaded on and maybe heat will aid is removal?

 

[mattthemuppet2]

If you want to hold round things securely without marring them, take a square piece of steel and drill/bore it to the shaft diameter. Then saw a slit in one side. Put the shaft in the block and clamp the block in a vise so that closing the vise closes the slot.

I would then heat the shank close to the threaded end with a propane torch, in case it's locked in as mentioned above

 

[erikmannie]

If you want to hold round things securely without marring them, take a square piece of steel and drill/bore it to the shaft diameter. Then saw a slit in one side. Put the shaft in the block and clamp the block in a vise so that closing the vise closes the slot.

I would then heat the shank close to the threaded end with a propane torch, in case it's locked in as mentioned above

I must be brain dead. I have a 3/4” tube block hanging in plain view on my pegboard.

 

[ddickey]

You should make some soft jaws for your bench vise with a V milled into them. Would be pretty easy then to hold the shank and turn the head.
Why do you want to take it off?
Why not just turn it down a little to the next size collet. I'd also cut it down a third, doesn't need to be that long imo.

 

[erikmannie]

You should make some soft jaws for your bench vise with a V milled into them. Would be pretty easy then to hold the shank and turn the head.
Why do you want to take it off?
Why not just turn it down a little to the next size collet. I'd also cut it down a third, doesn't need to be that long imo.

Being a little too long is one reason that I wanted to take it off. The other reason is that I feel like an R8 shank would be an upgrade because it has more material.