I was under the impression that when new hardware store locks were sold, they did not have the bolt holes positioned, drilled and threaded... that job was left for the purchaser or gunsmith for when fitting on the gun.
Shelby Gallien
They would have to be - the plates were generally casehardened also, not going to drill and tap that without ruining expensive bits. As I see it, the bolt holes basically go in approximately the same spots on every gun/lock, so there's no need to fuss with placement like we tend to do today. Period gunstockers clearly had no qualms about filing big notches across the breech lug or across the underside of the barrel.
Also imho (based upon experience with an awful lot of old locks) while there surely wasn't a 'standard' bolt size/thread, and certainly not over extended time into the 'late' period (i.e. comparing 1750s to 1860s), one heck of a lot of old locks of the early 18th century up through the early 19th century seem to match up fairly closely with modern 3/16 X 24 (10-24). I almost suspect that many locks sold through merchants or stores may have included a pair of lock bolts; there are a lot of old rifles out there with bolt threading a lot further up the shank than necessary. Like buying a pair of threaded bolts from Track for example that are threaded halfway up the darn length of the bolt shank to allow for a lot of breech width adjustment, vs buying a pair of blanks and threading them yourself so that the threads can't overtighten to kingdom come and crack the wood.
