I think in engineering a "drift" is a tapered tool that you drive into a hole in order to enlarge it. Thread drift must be then tapping a thread into that enlarged hole I guess..Jeremy
Now that's funny John When I put on a few Pounds I get thread drift and for awhile, it don't drift on back as It did when I was younger, if you get my Drift.
i think, technically, that's mid drift
How about Double Coin tires?