Optimal Bit Size for Template Routing
Advice on bits for routing holes in cabinets. August 31, 2009
We are a small production shop building amplifier cabinets. One operation we perform is an access hole 2.5 x 15" in 7/8" pine with 1/2" radius. Currently we are using a birch ply template mounted on the bottom and a 1/4" flush trim bit. We are having a few problems with it not producing a reasonable cut and we have to hand cleanup afterwards. We will be using a plexi template. I was wondering about the bit size and is a template bit more appropriate for this operation? Suggestions please.
(Cabinet and Millwork Installation Forum)
From contributor A:
There are some over and under-bearing bits available that have a spiral cutter on them, and they make a much better cut that straight cutters. OCEMCO is one company that I have got them from. Do a web search for them.
From contributor B:
Larger diameter bits can improve cut quality in this application for a couple of reasons. Small diameter bits have a limited chip flow and can load up with material, which impedes its cutting ability. Larger diameter bits produce smaller scallops due to their larger cutting radius.
My recommendation would be to try either a 1/2" or larger flush trim or the rabbeting bits you mentioned. Rabbeting bits are typically larger in diameter because of the bearing needing to be mounted on the shank. Also, check into large diameter flush trim bits with a shear face on the cutting edges. These bits cut remarkably cleanly and are not much more expensive than a good flush trim bit. contributor A's suggestion of the spiral bits is definitely another great idea. You can get solid carbide spiral flush trim bits that use a double bearing for stability. They cut cleanly and with less impact on the material.
From contributor C:
I use 1/4", 3/8" and 1/2" solid carbide spiral bits for guide bushing template work with solid wood and plywood and a 1/2" solid carbide compression bit for templating in melamine and veneer plywood. All bits are Whiteside and produce clean, chip free cuts.
From the original questioner:
All excellent suggestions! Thank you very much.