Gear Hobs - Shank type versus Bore type

[hanabie]

Hello,

I'm new to gear machining.
1. I know that shank type gear hobs costs way more compared to bore/keyway hobs. What are the pros and cons?
Why would people still choose shank type hobs?

2. Also, I have seen that hobs are usually held both sides when grinding. Is it possible to hold only one side and still produces close tolerances quality?

3. Does the bore type hobs affect the eccentricity tolerances when cutting? How do I know if it's installed paralleled along the axis?

Thank you

 

[mfgenggear]

hanabie

#1) it depends on the tooling that locates the hobs in the machine.
some gear manufactures have both. some only have arbor/shaft type.
To my experience I would prefer bore style hob, because it's cheaper, & more of a rigid
setup. tapered hobs where used because the cutter major diameter could be smaller.
& allowed for clearance issues with the parts.
manufacture of hobs can now get bore style hobs very small for very fine pitch gears.
#2) holding from both side is a more rigid setup. so it is preferred.
how ever holding from one side is doable.

#) each hobs have concentric bands on each side. these are used to indicate the hob in.
this insures it is running true.


Mfgenggear