I remembered you posting them before,
@WisJim, and I considered mentioning breast drills, in general, in
our little study, but ended up taking a narrower, less than exhaustive and evolutionary approach. No service was more frequent than valve grinding/lapping in the early days except maybe carbon scraping, and breast drills - let alone the reversible combination models, are actually mentioned in all kinds of early automobile mags aimed at home hobbyists and private garages, including early issues of
The Fordowner. And it's easy to see them being the inspiration for the lighter dedicated grinders that emerged, including from Goodell-Pratt, who, of course, made both. To be fair, it has to be said that it's also easy to see why they didn't last long for the service, though, too. They were heavy, and if there's anything that made valves worse than no lapping at all it was lapping done without a light touch. They were long, too. Access to the fourth cylinder was one of the main reasons why the early valve lappers had no crank at all, just a compact knob and a swing arm.
Very cool to see hanging in an extensive collection such as yours, of course!
