Double pass with round over bits

[Matt Gaither]

Howdy all, I'm trying to recreate an edge profile for a timberframe-ish project I'm working on. The profile is basically a large round over, maybe 1" radius, with fillets on the top and bottom. The picture with the lovely green and purple paint shows the original cut.

I've purchased a 5/8" round over bit that seemed like it could do the job if I took two passes on the same edge, the two passes being perpendicular to each other. I took off the bearing and ground off the little housing for the screw so that the two passes could line up. My problem is that I can't seem to get a continuous curve by doing this, and I feel like I'm just missing something obvious. The second picture shows one of my attempts. Any advice?
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[Scott Brandstetter]

I may not totally understand your dilemma but I'm wondering if you got a larger radius roundover bit if that would solve the problem.

[Prashun Patel]

If you took off the bearing, what's the bit bearing against? Is it the case that the 2nd pass is bearing against the cut away surface instead of the flat part of the beam as it should be?

Are your faces perpendicular.

I also in the get-a-bigger-bit camp - one with top and bottom fillets.

[Matt Gaither]

I don't think a bit exists that's big enough to get it in one pass... I'm fairly sure from the cuts on the original pieces that it was done in two passes. That little pointy shape in the curved corbel, where the purple paint ends, indicates two passes taken on two sides of the beam. I think I'm just dense on the depth or fence settings for one of those cuts.

[Matt Gaither]

I'm using the router's fence to keep the cuts straight. I'll get some close up shots of the cut I'm after and post them. I wish it were as easy as getting a bigger bit but I haven't found anything that comes close to this thing.

[Bruce Page]

I don't think you are going to get there without a bearing to control the cut. Carbide Processors sells some large radius bits.

http://www.carbideprocessors.com/roundover-bit-1-1-2-radius-1-2-shank-whiteside-2016/?gclid=CMXdteSUickCFYRCaQodEQ4CgA

Use an undersize bearing, 7/16" or 3/8" to generate the side undercut. Set your depth of cut to match.

[Prashun Patel]

MLCS Woodworking #8658.

I am trying to get my head around the geometry here.

I wonder if the problem is that you are trying to get a wider than 5/8" radius out of that bit. The best you can hope for is a 5/8" radius with super large fillets. To that end, it feels irrelevant whether you come in with perpendicular passes.

I think you might do better to just cut a rabbet on each inside face with a straight bit or table saw. This will create 3 corners. You would then roundover the center corner 5/8" without trying to flip the piece.

[Matt Gaither]

I think you're right. I was thinking I could get a bigger radius out of the bit with two passes, but that would only work if you could come in at 180 degrees from the first cut, which I can't. I'll experiment with the rabbet idea and see if I can get something decent.

My main issue is that I'm using new beams with reclaimed ones and would like that profile to transition nicely between the two.

Thanks for helping me think through it!

[Lee Schierer]

You are using the wrong bit. What you need is a beading bit not a round over bit. They look similar but make different cuts. Here is what a beading bit cut looks like. 325123 Check out beading bits here (http://www.routerbitworld.com/Beading-Bits-s/203.htm) A beading bit can do your cut in one pass.

[Bruce Page]

The only difference between a beading bit and a round over bit is the bearing diameter. As I mentioned above, you can set the undercut on a round over bit simply by changing the bearing diameter.