Weird Shank on Boring Head

[GlennW]

I looked at the Flynn site and it looks like the R8 shanks are $88.00, but it's the CAT 40 shanks are $275.00.

And they also make facing heads that use the same shanks...

[SteveHGraham]

F everyone's I, a shank from Shars costs $20. They don't have 2-20 threads, though.

[GlennW]

Flynn appears to use 1 7/16"-12 and 2"-12 threaded shanks from what I am seeing.

Have you removed yours yet to see what it actually is?

[SteveHGraham]

It appears that there is some "flexibility" in the pricing of those Flynn arbors. KBC charges $175.

I am starting to like the idea of using a stub, as long as it's safe. Anything that increases work-to-spindle clearance and does away with knee cranking is good. I just don't want the boring head to fly out of a collet and kill someone dear to me, i.e. myself.

I'm wondering if that arbor is some clever person's way of making a straight shank fit an R8 taper. Flynn offers National tapers and Pratt & Whitney tapers, but not this thing. That makes it look like a shopmade tool. The machining is very clean, like a factory part.

I see conflicting information on that arbor. One site says the threads are 2-12, but how can that be, in a 3" head? It would leave very little meat around the outside of the head. Another says it's 1-7/16-12. I can get a 1-1/2-18 shank, but I'm sure there wouldn't be enough material on it to take it down to 1-7/16-12.

[SteveHGraham]

The figure "2-20" was not what I actually saw. I should never try to think early or late in the day.

[SteveHGraham]

1-7/16 is 1.4375, and the thread depth for 1-1/2-18 is .048, so let's see...1.5 - 2(.048)...not going to work.

[GlennW]

I should never try to think early or late in the day.

I find that sometimes the middle part doesn't work too well either.

Criterion likes 20 tpi, so I imagine the Chinese do too!

The threaded area on a Flynn looks longer than most.

[SteveM]

It's a single point tool and the tool tip will always run concentric with the spindle axis regardless of shank error.

You are right. I stand corrected.

Steve

[GlennW]

It's a single point tool and the tool tip will always run concentric with the spindle axis regardless of shank error.

You are right. I stand corrected.

Steve

Yes, but you were correct in that if it was a boring/facing head shank error could come into play when facing.

[SteveHGraham]

I just hope it turns out to be in good shape. Seventy bucks is not bad for an American 3" boring head.

[Harold_V]

It's a single point tool and the tool tip will always run concentric with the spindle axis regardless of shank error.

You are right. I stand corrected.

Steve

Yes, but you were correct in that if it was a boring/facing head shank error could come into play when facing.

Yep! Any error would translate to an angled surface, although consistent with the centerline. You'd create a concave or convex surface, depending on the nature of the misalignment. All the more reason to achieve a dead perpendicular shoulder/thread pitch relationship.

Harold

[SteveHGraham]

The boring head arrived. It looks like it has never been used. It has a lot of little dings that look like they came from bouncing in a drawer.

I colored the taper with a Sharpie and stuck it in my mill spindle to see if it fit an R8. No joy. I can't even see where the taper made contact with the spindle. Also, the shaft is too short for the internal threads to reach the drawbar.

Not sure what to do with this nice stainless arbor. It must go with a spindle from Mars.