[HereinCS]

Does this look like a harmonic drive?

DNS HEAD, GEAR 2-39-54857 - eBay (item 150519042369 end time Mar-11-11 11:34:40 PST)

[jsheerin]

Looks like it - there seem to be teeth on the outside of the cup in one of the pics, but it's tough to tell for sure. I wouldn't buy it for that much money unless I could find specs on it to know what the allowable torque is.

[martyxxx]

Yes it is, but according to part number it seems to me that it is size 11, 1:50 ratio component set and size 11 is very, very small - around 30mm in diameter. Ask seller if you want be sure. If you plan to use it for fourth axis, look for size 20 and bigger... Look here: Products | Component Sets | CSF Series Gearing Components :: Harmonic Drive LLC , there are similar ones.

[HereinCS]

Thanks guys. I was hoping for a bigger unit. Harmonics LLC quoted me at over $2k each! Guess I'll keep looking on ebay

[giz]

Keep in mind that you'll likely want a gear head rather than a component set. You'll have to add your own bearing if you go with the component set.