Anybody see this old style holder before?

[Brento]

I found one of these in the tool box of free things i got. I know it is for threading but id love to learn more about the holder. Like why there is a big cut out on the bottom of it and such.
This may end up going in the pile of stuff to sell. Not 100% sure yet.

 

[hman]

The basic shape looks a lot like a parting tool holder I have:




From what I've read, the intent of the design is to place the pivoting action above the cutting line, rather than below. If you pivot from below (as with a less-than-stiff cross slide or compound), flexing the point of tool-to-workpiece contact downward in response to cutting forces tends to drive the tip of the tool deeper into the workpiece - positive feedback. Flexing from above tends to pull the tool tip away - negative feedback, thus reduced chatter.

As for keeping or selling the tool ... because of the size of the shank, this kind of tool holder is best suited to the "lantern" style of tool holder. If you want to hold it in a QCTP or such, you'll need to bolt or weld on a piece of 1/2" square stock or something similar. That might become a factor in your decision.

 

[mmcmdl]

I have a few of this style down the basement also . hman is correct as to why they are split . Also , if you decide to keep it and use it , mill the bottom of the shank to fit whatever size holder you may have .

 

[Brento]

I understand it more thanks. I think i may keep it after all. Just need to see what size hss it will take.

 

[mmcmdl]

Sometimes these will get you out of a jam , that's why I keep them hanging around .

 

[Brento]

Yea i have 2 armstrong holders that came with the lathe that i plan to use.

 

[benmychree]

It is what is called a spring tool, there should be a tapered nut/bolt in the countersunk hole to limit the spring or to make it solid with no spring. These holders tend to diminish the tendency to chatter.