Retired since June 2000
Welcome to the forum Greg, unfortunately it isn't possible for the template guide to be SMALLER than the cutter, the latter having to pass through the former with some clearance. The method for calculating the size of hole in the template is:Using a dish carving bit (from LV #16J26.70), I have to route 1/16" recesses in perfect circles.
If the photo upload cooperates, you can see my prototype (done with Forstner bit). But maybe I need more posts first.
I plan to use guide bushings inside a template that I can cut with a fly cutter on a drill press. So, I can make the template any size I need. (There could be some trial and error involved!)
Do you think I can use a guide bushing smaller than the outside diameter of my router bit (1.25")....IF I size the template accordingly?
decide on the size of template guide, the bigger the better, also the size of cutter, the simple formula then is: O/S diameter of guide minus diameter of cutter plus the size of the hole that you want. If you want to use a 1.25" cutter you will need a guide at least 1.5" diameter and supposing that you want to rout a 4" hole, then, 1.5"-1.25"+4"=4.25" hole in the template. If perhaps your largest template guide is 1.25", then use a 1" cutter and we now have: 1.25"-1"+4"=4.25"! No magic here Greg, the DIFFERENCE between cutter and guide in both cases is the same, 0.25", if we divide this by two, we refer to the OFFSET being 1/8". I do hope that this makes sense to you, if not, keep asking.
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