Fri Oct 23, 2020 7:02 pm by 6275LA
So I have been wondering about this for a while. Most keys (I'm thinking Schlage, Sargent, Yale, etc) have a top and bottom shoulder. These are all shoulder stop keys, so I fully understand the function of the top shoulder. However, I cannot think for the life of me of a good reason for a bottom shoulder. Now, in about 1983, Corbin did away with its bottom shoulder because it interfered with the face of the cylinder when X class cylinders changed from .509 plugs to .552 plugs and a recess was milled in the face of those plugs. I sometimes buy NOS Sargent blanks on eBay and the occasional one will have no bottom shoulder. Also, some old push key padlocks had keys with no bottom shoulder so it could be pushed in further in the lock to open.
The only "good" reason I can think they used bottom shoulders is because it visually balances the bow of the key, some of which were very ornate in the past. While I do find old Corbin X class keys with a cloverleaf bow and a bottom shoulder more visually appealing than one without the bottom shoulder, I do not find they operate differently...