Router Template Guide Size

Welcome teeto!

This will be the external diameter of the bush. For most jigs the diam. 30 is used (mainly 1/2" routers). That being said, you can buy a full range of diameters for various jig work. I have a 30mm bush on my 1/4" router for hinge recesses. I think the diam 16 is used on more complex jigs such as are used for dovetail jointing

 

most commercially produced jigs in this country for 1/2inch routers require 30mm bushes (worktop jigs are a good example)

most commercially produced jigs in this country for 1/4 inch routers require 16mm bushes, (hinge jigs are a good example)

so we dont get too many pedantic posts on this topic, this is only a rule of thumb

trend for instance make jigs requirng various size of guide bushes.

 

teeto

you may start with commercially made jigs but if your a serious diyer or a tradesman you will make your own jigs

 

My dovetail jig uses a 7/16" guide bush suppied withthe jig and I also have 16mm & 30mm bushes.
Someone using the routerforum in USA is constantly poining to his use or a 40mm bush for his template work.
When making your own templates it's easier to use metric cutters with a metric bush or imperial cutters with imperial bushes when calculating the offset for the template.
Making a mortice jig for a 1/2" cutter and 30mm bush was a nightmare of calculations.