"Deburring"--that the word I was thinking of by "drilling residue." These are strips about 2" long. I torched the 6" strip, then cut it to length bent it into a semi-circle, with a flat portion on each side, drilled on the flat portion. I couldn't jet a stainless J-bolt small enough (#8 or #10).
Couldn't have done it without the tip I got on the forum.
If drilling from each side, how does one get perfect alignment, unless you wait for the dimple to appear on the reverse?