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Magnetic Combination Lock Picture Safe

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Step 2: Machine Magnetic Tumbler

Picture of Machine Magnetic Tumbler
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Notes about making the tumbler...

I machined my tumbler out of 3/4" thick HDPE. It machines nicely, and is non-ferrous, which is important for the tumbler. If you follow the technical drawing, you will make a duplicate of what I did with one exception. I changed the 0.25" dimension in the top-view to .375" to allow for less precise turning of the tumbler in order for it to line up with the bolt that unlocks the safe door. There is only one 0.25" dimension in the top-view.

I machined this part on my HF mini-lathe, and a Little Machine Shop Mini mill and made my tolerances within 0.004". The lathe is unnecessary if you buy 2" HDPE rod, instead of using 0.75" thick HDPE block like I did; I had it on hand.

To faithfully reproduce the part's dimensions for the holes you would need a forschner bit, or preferably a 1/4" end mill. That will give you the 90 degree profiles on the bottom of the various holes.

 
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