Ignoramus8040 wrote:
I have a shank to hold slitting saws, gear cutters etc. It is on a
7/8" shank and is appx. 8" long.

Having never cut gears etc, I am concerned if, perhaps, this is too
long and would generate chatter. Is there any kind of a guideline on
this.

It's basically the same situation as turning with stock held in a lathe
chuck. Stickout shouldn't be more than 3X diam. I don't think that
Young's modulus is going to be much different for your arbor.

Bob