Anytime you create sparks you are ruining the hardness of whatever you are grinding. In other words, these grinding gizmos are not only shortening the life of the chain by removing more material then necessary, they are also ruining the hardness of the teeth and making the chain dull quicker.
Unbelievable, ROFL!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I guess the die makers who sharpen the progressive dies (they're carbide, if this means anything to you) that stamp the chain teeth are in fact actually dulling them with the surface grinder (it make's sparks btw)!! I gotta forward this one to my Die Maker buddies working @ Blount, Canada...........(They manufacture miles of Oregon chain per day), they'll put this beauty up on the wall!
Well, so much for your knowledge of basic metalurgy Sappy, stick with the framing jobs buddy, you don't have to deal with Rockwell "C" scale there huh?