Rounding over Arauco

[bzb]

When I did some tests on some scraps, I had major tearout when using the roundover bit. Since Arauco is basically pine, it's easy to tear out if you get overly aggressive. Here's what I did to get these results on the SLA Pros.

I'm using a Freud Diablo 3/8" roundover bit with 1/2" shank in a 1.5HP Rigid router with a fixed base.

1. Ensure the panel you're running the bit along is flat. No PL, no pits, no nails/screws making the ply protrude.

2. The bigger shank seems to help quite a bit. I used a 1/4" shank on the first attempts, but they're also cheapies. Quality does make a difference, mostly in the area of sharpness.

3. Crank the motor up to the fastest setting. Slower speeds definitely created more tearout.

4. Take two (maybe even three) passes, increasing the depth each pass. Biting smaller chunks not only reduces the chance of tearout, but also allows you to correct any mistakes on the next pass.

[Benj Ross]

Cutting against the rotation or with the rotation is a big one too. Generally doing a climbing cut (where the router wants to climb away from you) is more secure if you can keep control of the router. The blade is cutting into the body of the wood instead of the blade pushing the wood away from the body and tearing out more wood with it.

I figure you know that Bzb. I thought I would add it for anyone else who might read this.

I am starting on a set of these this week as soon as my plywood comes in. Can't wait to see yours finished.

Cheers
Benj

[bzb]

Good tip for those with a little more experience using the router. I wouldn't suggest it to novices on the router, as I think climb cutting can be dangerous, especially on smaller boxes like the SLA. I'm even nervous climb cutting just the ends (although that's how I always do the corners).

Do you notice that much less tearout from climb cuts? I honestly have never done a full length board that way.



For those not following, you can push or climb cut with a handheld router. If you're looking at the workpiece, a climb cut goes from right to left. The dangerous part about climb cuts is that the bit tends to pull the router, kind of like how a belt sander will just zip across your workpiece if you don't hold on.

[Benj Ross]

Good tip for those with a little more experience using the router. I wouldn't suggest it to novices on the router, as I think climb cutting can be dangerous, especially on smaller boxes like the SLA. I'm even nervous climb cutting just the ends (although that's how I always do the corners).

Do you notice that much less tearout from climb cuts? I honestly have never done a full length board that way.

I do. It depend a lot on what kind of wood and what direction the grain of your outside veneer is going on the plywood. With baltic birch it is not nearly as important as it works good either way.

Make sure your workpeice is secured either with clamps or blocks screwed to the bench around it so it can't move and then take multiple small passes like you said. If you take it slow there is not a huge amount of force pulling it away. If you keep your knees bent and your frame (upper body) somewhat ridgid, you can employ your body weight to control the router. It is the same using a large handplane. Your upper body moves with the plane not just the arms. With a bit of practice this gives pretty good control. YMMV. I usually do a light climbing cut first and then come back the other way over the established cut with good results.

As always, practice on a scrap or two first before trying it where it counts.

Benj

[bzb]

Great lesson, thanks. I'll try it out this week and maybe use the new technique on the T24s.

[Bill Fitzmaurice]

I only use 1/2" shank high quality carbide bits, and take multiple shallow passes. I never have tear out.

[Scott Brochu]

Another tip is to clamp a piece of scrap wood to the side near the corner so when you make your pass to the corner of the cabinet it will continue onto the scrap and if it tares or divots....well it's only scrap.
I will take a picture next time I do this to show you what I mean.

[BassMe]

I haven't rounded over ply yet, but on hardwood the easiest way we found for rounding over with consistent results is to lightly climb cut quickly to take the corner off, then slowly push against to finish the round over. This lead to far less tearouts (because the sharp edge was gone, that catches) but allowed us to get a very good finish on the round overs that required little to no sanding (not an issue if your using duratex etc anyway) because going slower lets the bit get multiple passes over the wood providing a smoother finish. This experience all came from building stairs for 6 months.

Again I dunno if this will work for ply, but it worked for us. When you are creating 60-100 stair treads a day with rounded over front faces you have to be fairly consistent.