Boring Head Conversion

[thestelster]

I have a large robust boring head which is fantastic. But because it only has one boring bar port, when I have to do large diameter bores, it is quite unbalanced, so I have to reduce the rotational speed, who wants to do that!! I have another boring head with an integral R8 arbor. It has 2 ports vertically and 1 port horizontally. But my milling machine has a 40NMTB taper. I also have and R8/40NMTB adapter. And I do not want to be changing draw bars whenever I want to use the smaller boring head.

What I need to do is put some sort of key or screw which will keep the top piece secured so it doesn't unscrew when removing the whole unit from the mill. I could Loctite it together, but I'd like to be able to remove the adapter if I have to.

 

[Chip Maker]

What about a roll pin?

 

[thestelster]

What about a roll pin?

Thanks @Chip Maker
But that wouldn't work. I'd have to drill through the hardened R8 shaft, and through the threads of the top piece. Plus I can't remove the adapter without taking the top piece off because the opening is smaller than the top piece.

I'm thinking more like a key that fits into the slot of the R8 shaft, and fits into a notch on the top piece (which I have to machine) and held in place with that screw on the adapter.

 

[Darren]

drill tap at the parting line between the two for a set screwc which would key them together?

 

[Susquatch]

drill tap at the parting line between the two for a set screw?

The photo looks to me like somebody has already done that!

@thestelster - I try to make sure all my tooling have arbours so I can use them on other tapers. My mill/drill was MT3 and my Hartford is R8. But I had a lot of tooling that came with my Mill/drill that I wanted to be able to use on my R8 Hartford.

Unfortunately, like yours, some of mine are integral. They will get sold with the mill/drill when its time comes.

I know it's a bit late for that this time, but something to think about for future purchases.

Edit - another option is to sell the R8 and buy a new 40NMTB.

 

[Darren]

@Susquatch , look at the circle i drew on. Thats where i am suggesting. The set screw you pointed to is the anti rotation pin, like in an r8 spindle.

 

[Hacker]

On my machine the drawbar is threaded at the top with a nut. I can adjust the drawbar to fit CAT40 and 40NMTB. No need for adapters.

 

[thestelster]

@Susquatch , look at the circle i drew on. Thats where i am suggesting. The set screw you pointed to is the anti rotation pin, like in an r8 spindle.

Yeah, there might be just enough room to do that. Thank you.

 

[Susquatch]

@Susquatch , look at the circle i drew on. Thats where i am suggesting. The set screw you pointed to is the anti rotation pin, like in an r8 spindle.

Ok, makes sense. I don't have 40 taper. I just assumed the R8 would end about half way up the 40R, and there it is a set screw! No biggie.