I want to fillet the top 4 outside edges of a block of wood. This is probably obvious, but I seem to be missing something. What’s the best way? I tried using a quarter round fillet router bit, but getting an exact zero to get a smooth transition from flat to round has proved to be very difficult. I considered doing it from an STL model, but that looks like it would take a very long time to machine.
So how do you pros do this? Thanks…
I would cut it flat, and then do the chamfer or round over with a trim router by hand. It would only take a few minutes and you can set the height and use the follower bearing. Just watch out for chipout.
If you plane your work surface/material before changing to the quarter round bit, I think you could minimize the witness line where the bit run out tengentially to the work…the blend would have to be completed with sandpaper/scotch Brite/files. Easier if we are talking wood.
This is what I’ve done, either with a trim router or on the router table.
Really??? I built this “machine” and there’s not a better way to do a fillet than to go back to hand routing? I’m bummed out. cry:
Regardless, I thank you all for your replies.
I think it’s a question of defining “better”. Certainly, if you run enough testing with your roundover bit, you can figure out the best way to zero it. Then, once you know, you can program it. As mentioned above, how flat the surface is matters a lot, and how parallel it is to the work plane does, too. And this Is a DIY hobby machine…
But to be fair, you asked how the “pros” do it, and really, for most of us it makes more sense to slap it on the router table or bust out the trim router, that’s all.
If I had to do tons or lots of wiggly lines, maybe not, but most I ever do is strait edges, so I’m with everyone else.
Give it a go, make some notes, take some pictures, and share. Lots of really smart people here who can probably help, even if they don’t do it on the machine, and it will make the community richer.
If I just need to cut out a square of plywood, I also just use my table saw. I think this qualifies under “using the right tool for the job”. If I carve a logo in plywood, I use the CNC. If I need to cut a circle, or even a rectangle with some detail, I would use the CNC. But there is some overlap, and you can do a chamfer with a V bit, but you’ll need to be careful (as you noticed) because any Z error is going to end up with width error.
Oh, I get it… I just had it in my head that there ought to be a way to do a fillet on the box I’m making. And I was surprised to find out otherwise. Onward, and upward! Thanks for your kind assistance.
When you have a fancy new impact driver, everything looks like a hex bolt, even the nails…
And there’s bound to be a way to make this thing do what I want! 
Since you’re looking for a CNC solution…I see that Fusion 360 has the ability to accept a Contour tool profile, so if you defined the tool, then it should be able to generate a tool path
I’ve never tried it, and I don’t know if you’re using Fusion.
I assume you’d want to first create a 3D solid that already had fillets as part of the model.
The simple solution would be to have a bullnose bit radius that matched your finished dimensions and then the pockets would have fillets automatically