What is this tool for

[projectnut]

H2 likely is the type of HSS the tool is made of; this is a common marking for tools of this sort.

It could also be the fit of the hob to the spindle. If I recall correctly before the advent of hydraulic spindles gear hobs had different tolerance fits to the spindle much the same as thread classes. I do recall some bobs being identified with a fit of H5 and H6. The tighter the tolerance the lower the number.

This was more important for precision gears when all components of the machine were mechanical. The hob had to fit precisely to insure proper depth and clearance. Now that most machines have hydraulically controlled spindles they can keep uniform and constant pressure against the work piece so an .0005" difference in fit to the spindle can be compensated for.

 

[Desolus]

It looks like a hammer to me...

 

[Desolus]

Yes, it is a gear hob. unless you have a hobbing machine, it is only good for a paper weight or doorstop.

Or a huge ass mill with a huge ass servo drive spindle and a huge ass servo drive rotary table...

 

[British Steel]

Or a huge ass mill with a huge ass servo drive spindle and a huge ass servo drive rotary table...

Spindle doesn't need to be servo drive, could just have an encoder on it and something like the electronic leadscrew controller (simple circuitry, Google should find it) for a stepper on the rotary table / dividing head? Would still need either the spindle or rotary canted at the hob's lead angle, but feasible for a home shop...

Dave H. (the other one)

 

[DaveInMi]

Yes, it is a gear hob. unless you have a hobbing machine, it is only good for a paper weight or doorstop.

Some day I'm going to gash a gear blank and try to finish it with a hob (table slanted to lead angle?). If one can use a tap or acme ready thread to make a worm gear, maybe the gash and hob would work.

 

[Desolus]

Spindle doesn't need to be servo drive, could just have an encoder on it and something like the electronic leadscrew controller (simple circuitry, Google should find it) for a stepper on the rotary table / dividing head? Would still need either the spindle or rotary canted at the hob's lead angle, but feasible for a home shop...

Dave H. (the other one)

I looked into servos and steppers for a large machine I was considering building and if memory serves high rpm high torc servos are much cheaper than the stepper counterparts. It should also be noted that a motor + encoder is just a wireing difference away from a servo motor; abet a crappy one.

Edit: You know you want this on your spindle http://m.ebay.com/itm/262387139592?_trksid=p2141725.m3641.l6368 ...

 

[Highsider]

It’s a thread cutting tool, used in toolmaking to cut the half round threads (or less than half round) on a quadrant shaped machine part that engages a threaded spindle piece, which controls the position of the quadrant. It’s used much like a worm and quadrant gear set, but uses thread forms instead of gear tooth forms.