Routing A Radius On An Outside Corner

[john bateman]

I'm using a 1/2" flush trim bit. The problem I ran into on all 4 corners was that the bit was cutting into the edge of the top past where the radius ended. It wasn't a lot but required getting a sander out and feathering in the depression.

That sounds as if your flush trim bit and bearing are mismatched. Like the bearing is a little smaller diameter than the cutter. Or your router bit is not at a perfect 90 degrees to the template.

[Ken Krawford]

That sounds as if your flush trim bit and bearing are mismatched. Like the bearing is a little smaller diameter than the cutter. Or your router bit is not at a perfect 90 degrees to the template.

The bit was a brand new, never been used Freud bit. I guess it's possible that the router was tipped but unlikely that I did it to all 4 corners.

[Mark Rakestraw]

I still think John is correct Ken. If the bearing is on the template and the cutter is going deeper it must be a slightly larger diameter. (assuming the router isn't tipped, etc.). I guess the other possibilty is that the pins do not hold the template perfectly even with the edge. Since its easier to smooth something that is a tiny bit proud rather than take out a depression I would shim something. You could shim the pins, or the template or the bearing with a piece of electrical tape -- any of those would effectively move the cutter out. Of course if it is caused by a difference in the bearing and bit diameters the shims might well need to come off when you change to a different bit.

[glenn bradley]

I'm using a 1/2" flush trim bit. The problem I ran into on all 4 corners was that the bit was cutting into the edge of the top past where the radius ended. It wasn't a lot but required getting a sander out and feathering in the depression.

This sounds like a couple of possibilities;
- The corner of the material and the template do not match causing the bit's cutter to contact the material where it should not.
- The flush bit is not truly flush (I've had this more often on bargain bits, never on a name brand).
- The "top" surface and the "edge" are not truly perpendicular; the router and bit have no way to compensate for this.