I believe I told this story before.
In our machine shop we made a collar with 2 o-ring grooves on the OD. The collar was about 2" in diameter and had a wall thickness of about .200. In the bottom of the o-ring there were flaws visable when the groove was polished to 32rms or better. We knew the parts wouldn't pass customer inspection so we sent the parts out to a lab for independent inspection, and it turned out to be sulfur stringers. These inclusions were not visible on the OD of the part, only in the bottom of the o-ring which was .100 deeper. The stringers were not in all of the parts but we trashed all of them anyway.
About 2 years after that our customer started specifying which mills, machining vendors were allowed to purchase material from. My guess was that they saw the same thing in their in house machine shop.
If these flaws were in a thin walled barrel, I have NO doubt that a failure would occur. Just a thought from the school of hard knocks.
Last edited by ithaca1; 06/05/16 09:31 AM.
