Thank you very much for telling me about the code tags. I've not used them beofre, so will practise thanks!
The reason for using gauges ("gages" is an alternate spelling, more common in the US) is just as said, it is a carry-over from the days when the keys were made from standard "wire" (the thicker wire is more like a rod, but it's still called wire to an engineer
Everyone has their own terminology for their own field and sometimes it gets confusing!
The bitted part was just welded on, originally in a forge and was skilled work alright. Especially as the lock was made in hand as well and the key was usually modified to fit the lock. I have keys 200-300 years old and they are so ornate. They look wonderful, but I cannot help seeing them as an engineer and marvelling at how you cut a shape like that out of a steel that is more like cast iron (VERY hard and brittle) - and thick! Not only that, but you have to make a similar "negative" for inside the lock to act as ward.
Sadly I don't have any of the locks, they seem to fair very badly from the weather over so many years, so only the keys seem to make it sadly.
Gives me a whole new respect for what could be done with those old tools and something I always mean to try for myself sometime, using the sorts of tools they would have had.
The other reason is it was an early attempt at standardising, if you know the diameter of the barrel of the key very precisely, you know enough of the sizes that need to be made inside the lock, to ease things a little. You can also use your standard-sized drills. After all, changing the size of the wire is easier than making a new special-sized drill.
Thanks for all the replies, it has really helped me thanks.
