Gears in gas powered core drill

[123Dog]

Were busting teeth in service
Tested them at 60 Rc,,, so I tempered them at 450C back to 48Rc
Boss flew off handle,,, said they are too soft now
Please advise

My estimate is that 48 is not too soft

Gear mat,l unknown

 

[lgearhart]

Dog, it depends on how they are breaking. If the problem was the teeth shattering, then dropping the hardness might have been wise. If the problem is fatigue at the root, then dropping the hardness is likely counterproductive. If wear is the problem, then dropping the hardness was not the best idea you had that day. Yet if it was case crushing, causing the surface of the gear tooth to spall, and the tooth to fail soon thereafter, then dropping the hardness was inconsequential.

The advice I could give would be greatly improved if you could say if it was a carburized, through hardened, or induction hardened gear. Any idea?

 

[Carburize]

At 60Rc it was most likely carburized, but as you say Lee, without a better description of the failure mode it is difficult to advise.

 

[123Dog]

Thanks for your valuable time


Will look at failed teeth under microscope