The first step I take in making a Cutaway is to take the lock apart and make a go at it with a caliper. I measure every dimension of the lock and transfer it over to CAD. Every width, diameter, hole, nook and cranny. This is one my favorite parts, it's calming and relaxing, and I love re-creating a physical object digitally.
CAD the Cutaway
The end goal is to open up the mechanisms the lock relies on as much as possible in order to allow us to observe the locks full functionality. The hard part is to keep the lock completely functional. If you look closely, you'll notice a "shelf" near the ball bearing, this is to keep the bearings from rolling out the left side. It's not actually needed on the right side, but I wanted to keep it symmetric.
CAM the Cutaway
This by far is the steepest learning curve I've went through in learning how to CNC. Pathways are created taking into account the type of material, depth of cut, width of cut, feeds and speeds. I normally start and base my calculations to mill 0.0015" per flute. This is pretty conservative, it just adds time, I'm not in a hurry and don't want to burn through end mills. For this, I used a 3/32" 3 flute variable end mill with a Zirconium Nitride (FANCY) coating at 10,000 RPM and 45IPM (Inches Per Minute). If you want more details PM me somewhere and I'll be more than glad to chat. This would bore normal people.
The APTC14 Cylinder
The American Padlock cylinders are smaller than the standard KIK cylinder. This makes it a bit more difficult to mill just because it's tiny (work holding, tolerances, etc). Also, you kind of want the springs and pins to stay inside when you open the lock :) . traditionally a "slotting" function has been used. By sacrificing an embarrassing number of locks, I found a sweet spot for the width to keep the pins/springs in tight and still to open it up as much as possible. For this I used a 1/16" end mill and a more complex pathway than a slotting method to cut a wider cut than just 1/16". Also notice the pinstack cuts follow the profile of the body.
I really am proud of the end result. My favorite part is the chamfer around the pockets. Amazingly with Fusion360, the chamfer is super easy to program.
The one thing that bugs me about this lock, it's a 6570. American Lock labels this the 5570, the difference between a 5570n and a 6570? The 5570 has 5 pins. Guess how many pins the 6570 has.
One crappy caveat, depending on the date code on it, the model number position varies around +-0.020". I have to alter the CAD/CAM for each different code to make sure it's centered.
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