Hard Bolts and Harder Drills

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Posted to Technical Theory Forum on 5/15/2017 48 Replies

What exactly decides how difficult a bolt is to drill? I had thought the Grade 8.8 10.9 or 12.9 would be the defining factor. Not so.

I grabbed a selection and used a file to test the hardness of each one:

[Hardness Comparison of Bolts]

Hardest on the le... Login to read more.

Files Referenced:

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