This Yale, 4 pin push key padlock is an interesting case study. This particular lock was most likely manufactured prior to 1930 based on the cast key logo. These padlocks are mostly found in a steel and bronze material, although all bronze versions were made. I was able to open this lock by inserting some shim material between the lock body and the cylinder,though the cylinder and hasp are really one component. Hasp tension can sometimes be used to open these padlocks while quickly scrubbing out a rake pick across the bottom pins. This technique or even single pin picking may not be as easy as one might believe. Yale had the foresight to manufacture their top and bottom pins with tiny serrations causing them to bind and false set.
My Yale padlock was another Ebay find sold without a key and should be a testimony of "buyer beware". Because these locks have a nickel-silver material for the bottom pins and the keys were made of a much harder steel material, the bottom pins are very susceptible to wear, causing the keys to no longer work. The problem becomes even more complicated when certain pins represent a zero depth cut. As with my lock, the second bottom pin was a zero cut and wore down further than the working tolerances will allow. Now the top pin traps into the cylinder.
After the lock was shimmed open, I discovered a unique square hole in the bronze button present on the top of the lock. This button reminded me of the seats often found in many faucets, which meant the button may have threads as well. So, I made a tiny seat wrench out of bar stock. The button did have threads and once removed the hasp spring was revealed. This hasp spring also retains the cylinder. I soon learned that my lock is actually a re-keyable padlock. In order to completely remove the hasp/cylinder the hasp spring must be pulled slightly out at a 45 degree angle, but not removed. Even the slightest protrusion of this spring into the cylinder hole will prevent the cylinder from coming out.
At this point, I can replace the second pin and make make a new key. The process is merely academic. After I collect more of these push key locks l will post some pictures of some of the keys as well.
