Proper router bit for installing center fin box


Hello all::::just started shaping and glassing (just decided to be broke forever):::::and am wondering about router bits for center fin installs. 


I will be using the fins unlimited 10.5" box and the Makita router they have on Shaper Supply and Foam EZ   

I see lots of instructions on how to make templates and route - but very little talk of what actual bit should be used::::is it a 1/2" bit or 1" bit? Is that measurement for the diameter of the bit? 

Any links or pictures of bit suggestions would be appreciated. Thanks for the help.





The above bit dia. matches the corner radius on the corners of the box.       Quarter inch shank is ‘‘normal.’’

My plunge router I use for fin boxes is 1/2" shank.

3’’ over all length.

2" of cutting blades.

1/4" has trouble with stringers.

I use a 1/2" diameter bit with a top bearing the same size. What I’ve always known to be called a " pattern cutting bit" because you place your pattern/template on top for the bearing to ride against. 1/4" shank is fine, 1/2" is better for less vibration/trouble as Barry says. 

Aloha Barry,

Multiple shallow cuts, will get the job done.      I know you know that.      I make the comment for the benefit of other hobbiests.          If I were still in the trenches, doing production, I’d have moved up to a 1/2 inch router long ago.       I’m still using my 1964 quarter inch router.     Many’s the box, has been mounted in solid Redwood Gun stringers.       Carbide bits make the job so much easier.       Well worth the higher price.

Thanks for the feedback guys:::would this bit be something like you’re describing Barry?

Yeah, that will work.

Most router jigs for long boxes are set up for a 1/2" full size router.

More power.

More RPM’s.

I prefer the full size as I sometimes route really big stringers.

Never had much luck using my trim routers for bigger jobs like Longboxes and routing my outlines.

Ah ok I see the difference between full and trim — something more like this then:::

there are so many different shapes—is that the right style bit?