Cutting circle with router

[Dick Carner]

I have followed with interest a previous thread several years ago regarding cutting circles using a router. I am installing two under mount sinks in 5/4 curly maple. I do have up cut spiral bits but after 30 years of use all of them have gotten nicked up and dull. It goes without saying that the edges of this cut out need to be very clean - no burn marks, etc. I have a DW625 that I'll be using and a circle cutting router jig. Definitely want a 1/2" shank. My question is what diameter cutting diameter would one recommend? I'm looking at a Whiteside Router Bit --[RU5150]. It's a standard spiral bit with up cut solid carbide with a 1/2-Inch Cutting Diameter. I am open to suggestions. TIA

[Jerry Miner]

That bit would be OK--but test on scrap-- it might give you a little tear-out on top.

When I do these, I make a template out of mdf, cut a rough (undersized) hole with a jigsaw, then use a pattern (top bearing) bit with the template to clean up the hole.

Easier to take light, clean cuts this way, IMHO, but YMMV.

[John TenEyck]

I usually use a router on a trammel; saves making a template. And I don't rough cut it first either, not because I'm lazy but because you end up with a better cut when the bit is supported on both sides. A 1/4" bit works as well as a 1/2" one, too, because it's supported on both sides, and I only take about 1/8" per pass. Whiteside, Bosch, several good choices. Also, I route so that the bit thinks it's climb cutting on the show surface. I say thinks it's climb cutting because it's not really a climb cut as the bit is fully engaged on both sides.

John

[lowell holmes]

I would consider cutting a hole 1/4" under size and then cutting it to diameter.

[Jim Morgan]

I usually use a router on a trammel; saves making a template. And I don't rough cut it first either, not because I'm lazy but because you end up with a better cut when the bit is supported on both sides. A 1/4" bit works as well as a 1/2" one, too, because it's supported on both sides, and I only take about 1/8" per pass. Whiteside, Bosch, several good choices. Also, I route so that the bit thinks it's climb cutting on the show surface. I say thinks it's climb cutting because it's not really a climb cut as the bit is fully engaged on both sides.

John

Just to add to what John said, if you are using an upcut spiral bit (the better choice here), you should work from the underside of your countertop. This will help ensure a clean edge on the top of the maple.

[Bohdan Drozdowskyj]

That bit would be OK--but test on scrap-- it might give you a little tear-out on top.



If you climb cut on the outside edge, and do it very shallow for the first cut, there will be no tear-out.