R8 Arbor Questions

[RonRock]

I need an arbor for a Bridgeport No2 boring head. Seems easy enough to just order one wait a week and Bob's your uncle! No such luck. The Bport boring head is a 1 1/4 x 12 thread. Pretty sure that is true, my arbor is stuck in and damaged. But I'm sure that it isn't the more "typical" 1 1/2 x 18 thread that is easy to find.

It has been suggested to me that I buy a 1 1/2 x 18 and turn the threads down and turn in the needed threads.

Are the arbors hardened? Are R8 arbors generally hardened? Or are they usually soft enough to machine? I actually have a couple other oddball arbors that I need. One for a Tapmatic tapping head that also seems to have an odd thread that Tapmatic don't make an R8 arbor for.

It's always something.

Or maybe I have missed the boat and someone here can point me to an arbor that will fit my No2 boring head. That would be great, but I still have other needs for odd arbors.

 

[ErichKeane]

Why not just scratch-make an R8 arbor? The lead-in-taper is a touch of a pain to indicate in (use an existing collet/arbor to do so!), but the rest is pretty simple. Even easier if you have a taper attachment. I'd suggest 4140 HT.

 

[RonRock]

That is also a consideration. Thank you, ErichKeane.

You answered my next question of what type steel to use if I decide to take that leap.

 

[ErichKeane]

I did a bunch of googling and it seems that most arbors are 'hardened'. If you really wanted your arbor hardened/ground, you could always just make a thread adapter. I found on amazon a 3/8-24 and 5/8-16 threaded arbor for ~$25 shipped, you could potentially turn a thread-to-thread adapter for your oddballs.

 

[RonRock]

Would that be accurate enough for an arbor? I considered that, but was concerned that there would be too much "slop" in the threads. May not matter for either a boring head or tapmatic.

Are you able to make a hardened arbor soft enough to work with then re harden?

With all of that it might be best to just start from scratch and make my own and heat treat before final grind. Sounds easy. Unfortunatly way over my head and ability level. But I might try anyway. Not sure if the old Logan is up to it.

 

[Lo-Fi]

Look for R8 soft end blank:

3 MORSE TAPER BLANK END ARBOUR SOFT STUB 40MM X 40MM WITH 12MM DRAWBAR RDGTOOLS | eBay

SOLD BY RDGTOOLS. THREE MORSE TAPER BLANK END ARBOUR. WITH 12 MM DRAWBAR THREAD. TAPER SHANK IS HARDENED, END IS SOFT TO ALLOW MACHINING. CAN BE USED TO MAKE END MILL HOLDER, DRILL ARBOR, THREADED ARBOR OR MANY OTHER APPLICATIONS.

www.ebay.co.uk

A UK link, but you it'll give you the idea. I tend to keep a few in so I can do little jobs like this when I need.

 

[ErichKeane]

Would that be accurate enough for an arbor? I considered that, but was concerned that there would be too much "slop" in the threads. May not matter for either a boring head or tapmatic.

Are you able to make a hardened arbor soft enough to work with then re harden?

With all of that it might be best to just start from scratch and make my own and heat treat before final grind. Sounds easy. Unfortunatly way over my head and ability level. But I might try anyway. Not sure if the old Logan is up to it.

Presumably your threads would be cut in the same operation, so they should be concentric. Id consider turning the outer-threads ON the arbor though.

That said, Lo-Fi's soft-end-blanks are likely your best bet

 

[RonRock]

New to me. I'll check them out.

 

[darkzero]

The import one I bought was really only case hardened. It was also 1-1/2"-18 that I turned down & rethreaded to 15/16"-16". Was also able to tap the center.

 

[mmcmdl]

I believe I'm holding one in my hand . I can't remember what it was on , but I sure don't need it . I'll take it into work and check it out .