ceetee

Since I was a quality engineer when I was working, I place a large importance on numbers, and being correct. While checking through a lot of woodworking notes, I came up with the solution to my problem - and it works. So here's my answer to making a male circle jig to use on my 12" finished wood boards so that I leave a 1/4" wide lip around the entire circumference of the top surface. If anyone has a easier way to accomplish the same thing - I'm all ears/eyes!

This answer is based on an imaginary beginning male jig of 12". Subtract the outer diameter of the guide portion of the bushing twice. Then subtract the lip width twice. Then add the difference between the bushing diameter and your cutter diameter - again twice.

12.000 diameter of lazy susan board
- 1.250 .625 (5/8) bushing diameter times 2
- 0.500 .250 (1/4) desired lip width times 2
+ 0.250 .125 difference between bushing & bit diameter times 2
_____
10.500 = male template diameter

This type of approach will work when constructing male templates, especially circles. Female templates will require a reversal in additions and substraction. I've used this concept before when making both male and female jigs - though it has been some some now. It will apply to both linear and radial dimensions.

I should have solved and confirmed my solution the way I ended up doing it - which was drawing everything to scale and checking my numbers more than once - before posting my question on this site. The answer was in my old notes but I was hoping someone would offer me this logic.

Thank you all!

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No one is too old to learn or to practice good safety!