Modding the lock on my 1971 Nishijin "A"

[SteveFury]

I want to build a semi-sealed cabinet for my vintage pachinko so I wanted to fix the lock so any screwdriver or properly grooved flat key will open it. I suspect it is a common lock for the period with a crooked keyhole.

First is a couple photos of the lock itself, the lock has a number 7 stamped on the rear:
Front.JPGRear1.JPGRear2.JPG

The lock is held together by 4 expanded tabs shown below:
SplitTab.JPG

Using a big channel lock pliers, I was able to squeeze the spits on each of the 4 tabs enough to pry it apart with a common screwdriver:
Opening.JPG

The 3 plates inside are arranged this way (The parts had fallen out when I took it apart but this is how the inside plates went):
Parts.JPG

The cylinder contains no springs or actuators like a traditional lock does. All the key does is go flat with the bottom plate, and when you turn the key it will directly move the slider which actuates the external door latch mechanism. Extremely simple.

It has two additional spring loaded plates which keep the key inserted while being turned.

In order for me to be able to open the lock by only turning the key shaft with a screwdriver, I had to make a tab to fit the bottom of the key slot.
I used a large size steel nail for the tab material. I ground the nail flat on two sides just enough to fit very snuggly into the key slot to stick out like a key would have.
Note: I took particular care to make it the correct length to properly fit into the slot in the slide. I did a bit more grinding to ensure a proper fit for operation.

I then mixed up a spot of "JB WELD" which is the strongest epoxy I've ever seen and applied it to the end of the steel pin I made and glued it into the key slot. The fit was very tight and I used a pliers to ensure the steel pin sank to the very bottom of the slot. I wanted a very tight fit because this is a potential breaking point and it simply MUST be tight.
Below is how the steel pin looks as the epoxy cures:

Actuator.JPG

You can see below how the key slot and steel pin move the lock slider:
ActuatorInPlace.JPG

I will be discarding the two extra plates which keep the key from being removed while operating the lock since I don't need them anymore. Besides they just get in the way of my steel pin and prevent it from working properly.
I needed to compensate for the space these two plates formerly occupied so I added a couple shiny washers to keep the slide flat against the bottom. (See below)

Washers.JPG

That's it, I am waiting for the epoxy to finish curing before reassembling and testing.

A few light taps of a hammer should be enough to squeeze the 4 split tabs which hold the lock together- enough at least to reassemble the lock.

I haven't tested this mod yet but I'll let you all know how it goes in a day or so after the epoxy has completely cured.