How much to shim a router fence?

[Louis Brandt]

Hello,
I’m still wrestling with the idea of trying to put a bullnose along the edges of the mantel shelf for my fireplace mantel project. I have a router table but no router that fits it yet, but I’ll buy a router for it if I can convince myself that I can successfully do this operation.
My question now has to do with the outfeed fence issue. I’m a novice, but from what I’ve learned, I know that the outfeed fence has to be slightly forward of the infeed fence to make up for what the bit is removing in a full bullnose cut. My Bosch router table has two 1/16 inch shims supplied for this purpose. The outfeed fence itself cannot be moved forward, but the table is designed so that one or both of the shims may be inserted.
My question is, how will I know how much to shim the outfeed fence? Is this just a case of trial and error, or is there a rule of thumb for this?
Louis

[Vaughn McMillan]

Louis, the trial and error method should work...use some scrap wood, of course. That said, I'd suggest that you purchase a roundover bit instead of a bullnose bit. The roundover bit will have a bearing that negates the need for the fence, and is easier to control IMHO.

As mentioned in your other thread, with a roundover bit and some sandpaper, you can make a beautiful bullnose edge.

- Vaughn

[Charlie Plesums]

My fence has the adjustment, and on the rare occasions when I use it, the adjustment is very small. Like a jointer, the outfeed fence is aligned with the cutter, so with a 1/16 inch shim, you would be taking 1/16 inch off the final width of your work, etc.

[pat warner]

Depending on several factors, the cut can be quite demanding .
With an offset fence you don't have the luxury of stage routing, you must waste the whole edge in one shot.

As such, minimize the offset, say to .004 - .010". No need to make a lot of chip here.
See set up at the Offset set fence link.

[mark koopman]

I agree with Vaughan on this one. 2 Passes with a roundover bit and your good to go, no need for fence offsetting or anything.

[Jerry Olexa]

I always go 2 passes w roundover bit to get a bullnose. Just a quick flip and route..no adjustment needed