I've just made my 1st template and used it to rout out a set of hinges . I was very surprised to learn that the usual approach was to use a guide bush and a straight 2 fluted bit. This involved attempting to make the template 1.65mm larger all around the template to accomodate the offset between the 16mm guide bush diameter and the 12.7mm width of the cutter. (16-12.7)/2 = 1.65mm. But- after researching I was getting the impression that some may be using a special router bit possibly a template profiler with top bearing (on the shank) and mortising ability. I can't find any definitive information on this and am wandering if I'm getting confused with using this bit to actually make the template or to recess the hinge following the template. If I can make my next template exactly the same size as the hinge then that would seem to me a lot easier and much less likely attract error. So - can anyone confirm whether the second method is possible and exactly which type of bit I should use?
This bit is called a "hinge mortising bit"* but it looks to be essentially like other top bearing router bit.
The one difference between this and other top-bearing router bits is that the maximum depth of cut on this one is fairly shallow, which is what you'd want if you're routing into the edge of the door to recess the hinge. This particular one comes in several depths of cut, but to me, they all appear to be to deep for a standard door hinge.
The advantage of a guide bush is that you can use any old straight cutting bit and adjust the depth independently of the guide. With the linked bit (or a similar one) you're stuck with routing to the depth of the cutters, or you have to make a template the thickness of the cutter minus the depth of the mortise you're looking for.
* Amazon.com link - no specific brand/retailer recommendation implied