This lock fascinated me with regards to how it worked. I learned a long time ago that my brain does not think well in 3D. Although I had the pattern for how to make the lock, it was still not obvious to me exactly how it worked.
Here is how the finished lock looks in Tim's 2nd book....
I tried using Google's Sketchup 3D drafting package to lay out the design, but I am a novice using this drafting package and it took me a long time to learn how to draw using it. Here is my crude 3D view of the pins and the shackle:
I laid out the lock design in 2D, looking down on the lock. Once I did this I saw how it worked. Basically, the pins for the 3 numbers you don't want to press, allow the shackle to pass by. If you incorrectly push one of these 3 pins in, the pin locks into a mating hole in the shackle, not allowing the shackle to pass by.
On the 3 pins that you do have to press in, the pins start out engaged into the shackle. When you press the pins in, they disengage from the shackle, allowing it to pass by.
When I laid out the pattern in 2D, I noticed the author only had 1/8" engagement on the 3 pins you have to press in...and the pin travel was not the same as for the other pins.
The author's original design had the same pin design being used on all 6 pins...and is shown in the ORIGINAL Design above. This design did not seem to make sense to me. On pins 1,5,6 you start out with interference as shown in the green triangle...and the pins move in 7/16" until they bottom against the shackle. On pins 2,3,4 you get very little travel on the pin.
I changed the design to have 2 different pin designs...one for pins 1,5,6 and one for pins 2,3,4 as shown in the NEW DESIGN above. On the pin for 1,5,6...the slot in the pin is 7/16" and 7/8" from the ends. On the pin design for 2,3,4...the slot in the pin is 5/8" and 9/16" from the ends. I made the pins and my design works very well with equal pin travels.
I made 2 lock bases from walnut to yield 2 locks of this design. On the first lock, I inserted a 3/4" dowel to make sure the shackle hole was centered....as measured by looking to see if there was equal space in the 1/2" holes...and it was fine. Somehow the 2nd based shackle hole was not vertical! I'm going to try to salvage the based by gluing a 3/4" dowel in the shackle hole and then re-drilling the shackle hole. The author points out it is critical to make sure the 3/4" shackle hole is drilled correctly vertically..and he is correct!.
I also had some trouble with the 1st lock base shackle holes matching the shackle. I have made lots of shackles before and never experienced this before. One should check the centerline distance of the shackle holes to make sure they match the shackle centerline. I was able to sand and make the shackle fit the shallow hole side ok.
My 3/4" Forstner bit was not long enough to drill the shackle hole to depth. I went to Ace Hardware and bought a 4" extension for my 3/4" spade bit to drill it to depth. I ordered a 4" extension designed for Forstern bits with 3/8" shank diameter for future projects.
Here are the individual pieces hanging from my temporary drying rack:
Here are the individual pieces of the lock. Note that I chose to not cut out the curved section of the base like the pattern. I like the square lock look better. I also designed a Mick knob, so my co-worker Mick could be able to dis-assemble the lock and see how it works.
And the finished lock.....