Deformation of Allen Head Screws: Impact or Wear?

[drag88]

Hi all just a simple question about the hole of the Allen head screw becoming round/circular after repeated use of a Allen key on it. From what I read so far it should be a form of wear. I am thinking of abrasive or impact wear, but not sure which is it. Can anyone answer this? Thanks.

 

[Ranger Mike]

no way would hardened spec allen bolt round out IF you use the proper wrench..i have rounded allens i found on the original race car simply because it was not known if the bolt was inch or metric..ifin you got a metric allen and use an INCH wrench, you can round them..especially if they are rusted

 

[DickL]

I've seen many Allen set screws get rounded when using the proper key. They have been over torqued and the metal has deformed, not worn. I suspect that the deformation is happening to both the key and the screw's recess. I've not seen it happen in larger size Allen headed cap screws (say 1/4 in. and larger bolt size).

I don't have any experience (or at least much) with use of an impact wrench with Allen head bolts. I can imagine that an impact wrench could readily do damage to the head.