A bit of pondering about the difference between pricking and overstitch wheels...
Overstitch wheels as their name implies, in addition to marking stich hole locations, are also used to refine the appearance of stitchwork by running the wheel to and fro over stitchwork that has already been laid into a stitch groove. I'd guess that a pricking wheel wouldn't produce a pleasing result if used similarly.
To expand a bit more on that thought, maybe it's me but I associate stitch groovers with overstitch wheels, but not with pricking wheels (or chisels). With a stitch groove, the stitchwork is almost forced to lie down into the groove, making the stitches lie in a straight line. I don't see pricking wheels or chisels used much if at all in conjunction with stitch groovers. With a pricking wheel or iron (and no stitch groove), the stitchwork is designed such that each stitch ends at the bottom of the angled slit left by the awl and the next stitch starts at the top of the next slit (or vice-versa). Thus these stitches lie in a sort of zig-zag pattern that has a different "eye appeal" than stitches that lie in a straight groove. I know that stitch grooves are intended to protect stitchwork by allowing the stitches to lie below the surface of the leather. But in "American" leatherwork I see grooves used almost universally even where there would be no concern for friction or contact against another object. In contrast, the British stitching I see needs no stitch groove to lie down into the surface of the leather, apparently if the thread is pulled tight enough.
Therefore, while we are on the subject of stitching nomenclature I have a question.
I know for example, Nigel, that you prefer not to use stitch groovers for "external" stitchwork (stitches that "show"). That seems to be consistent with the work of other British Master Leatherworkers I am aware of such as Valerie Michael, the author of an excellent book titled, "The Leatherworking Manual." Is this lack of use of a stitch groove consistent enough across those who use pricking chisels or wheels to term it the "British" style of stitching? If so what might one call work that almost uniformly combines an overstitch wheel with a stitch groover on external stitching? I trace that trend to Al Stohlman's famous book, "The Art of Hand Sewing Leather." I'm not sure where it came from before that. I suspect it has a Mexican heritage, since much of the American Western style of leatherwork and carving has its origin south of the border. For the sake of discussion, let's call it the "Stohlman' style.
The answer to that question would clarify my thinking and permit a more consistent and precise dialog amongst us "leatherheads."
Thanks,
Michelle