Do Two Corner Round Passes Equal One Bullnose?

[Curt Rowe]

I need to mill up some 1.5" diameter bullnose for the window trim on my house. After that I can't think of another use for a 1.5" bullnose cutter. I was thinking that if I bought a 3/4" corner round, it would be more likely I could use it in some other project. It's also a lot less expensive. Given that I don't have a lot stock to process, the extra work is minimal. My question is if a pass on each side of the stock with a corner round will result in the same profile as using a bullnose cutter. It seems that it should. My only concern is if the corner round didn't cut a full 90 degrees of a circle. I'm looking at an Amana A-30-114.

[Don Wurscher]

If you are going to use a 3/4" round over, you can use the pilot bearing for the first pass, but you will need a fence on your router table for the second. I use a fence for both passes saves time, even then I sometime need to touch the center portion up with sandpaper. Using the pilot bearing can also leave a mark if you press up against to hard with soft wood.

[Peter Quinn]

Usually there is a step at the center of the bullnose when run in two quarter round passes because the bearing has a sloping reference for the second pass. This is easily sanded and hardly noticeable. Amana makes tapered bearings for some of their 1/4 round cutters just for is purpose, you run the first cut with a regular bearing then switch to a tapers nylon bearing for the second pass, keeps the alignment better. They are really meant for solid surface which is not so easy to sand but work for wood too. I personally would not like to run a 1.5" bullnose on a router in any event and have done it with a 3/4" quarter round on occasion..

[Yonak Hawkins]

I did it on all the window sills in my house. I didn't set it up to do a perfect round-over .. there is a narrow flat between the top and bottom radiuses, but sanding hides it very well. Testing on a scrap piece that is the correct thickness, you can determine how high you can adjust the cut while still bearing on the edge.

[Wade Lippman]

I bought a 1.5" bullnose at an auction and have never used it! Two quarter rounds works fine and is easier.
So if you want a good buy on a 1.5" bullnose...

[Curt Rowe]

All your replies reinforced what I thought. I just wanted to make sure I wasn't making some sort of dumb mistake. I didn't mention that the cutters were for a shaper. At about $200 for the bullnose and half that for the quarter round, it's a nice savings. I could get a rub collar. Using the fence made more sense for the reasons you gave.

[Lee Schierer]

If you are going to use a 3/4" round over, you can use the pilot bearing for the first pass, but you will need a fence on your router table for the second. I use a fence for both passes saves time, even then I sometime need to touch the center portion up with sandpaper. Using the pilot bearing can also leave a mark if you press up against to hard with soft wood.

This is exactly right.

[Peter Quinn]

All your replies reinforced what I thought. I just wanted to make sure I wasn't making some sort of dumb mistake. I didn't mention that the cutters were for a shaper. At about $200 for the bullnose and half that for the quarter round, it's a nice savings. I could get a rub collar. Using the fence made more sense for the reasons you gave.

on the shaper you can use a back fence with a power feed and eliminate the step entirely even with two passes. We used to make dowels in 4 passes that way! An insert knife or a euro block cutter would be cheaper on the shaper for a full bullnose, amana has a profile knife for around $20 that does window sill nose cuts, may be worth a look.