I need to cut a bunch of these out of reclaimed fir uniform thickness about 15/16"

I think the peaks will split on a router?

Any ideas would be appreciated.

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By router do you mean CNC? I can run both CW and CCW with mine, so using left-hand tooling as well as right-hand would allow this to happen with no tear-out. Very useful for things like this. Other option would be to leave part over width, cut the parts, then trim the width to remove tear-out.

A slight radius (1/16 or so) on the corners will help somewhat, but you will have to run some tests to see. Some fir blows out no matter what you do. I would also try cutting oversize by a smidge, followed by a new & sharp downshear finishing bit. A sure fire way would be to route out the scallops on an over-width part, then rip to width on a tablesaw. I've fiddled plenty with trying to get cut cycles perfect and later realized I should stop overthinking it.

Thanks guys.

SG

What brand of router reverses?

All routers that I've operated (Weeke, Komo, Multicam) can rotate both directions. I think it's pretty common.

can you make the holes with a hole saw and then rip the board in half?

Nicko

Could but it would take too long

I believe all spindles will run both directions - I just had to contact the manufacturer and they sent me a little relay I had to wire in place, then they walked me through a pretty easy programming of the vfd. Probably not a 1/2 hr. job all told.

I end up using left-hand tooling a fair bit for sticky situations like this, and it's like magic. Takes just a bit more time to program, but very much worth the effort.

At the risk of stating what should be obvious, you must use left-hand tooling, and either a left-hand toolholder, or supposedly ball-bearing nuts will run either direction safely. I have a couple of left hand tool holders which I have marked so there is no confusing them.

You don't need to run the CNC spindle in reverse. Matter of fact that just won't cut at all. You just need to travel in a climb cutting direction around the part with the spindle running in the standard rotation direction.

BH Davis

I have spent the last two weeks cutting white oak with a LH rotation, chipbreaker down spiral - it is necessary to use an M04, rather than M03, but I'm quite sure it works.

These twisted mouldings were made with both a 1" ball end and .375" down spiral, both in LH rotation on the left side, and RH on the right side. Loss was nearly 100% on the left side using RH rotation, no matter how carefully it was programmed using climb cutting. The parts were made by gluing up at a 45, so the grain is converging toward the center, making the direction completely predictable.

We made several hundred both for this circular wainscot and flat version for walls, so we got very good at the process, but it would not have been possible w/o LH rotation.

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split the cut into two toolpaths. Cut the bottle cradles in one pass (climb cut) beyond the top horizontal cut. Then follow up with the horizontal top cut with the grain. I can't guarantee no breaks but I think it will be clean. And faster than breaking the toolpath into cw/ccw cuts

I think you are all overthinking this.

Make a jig that clamps two widths together and then cut circles. When you take the parts out of the jig you will have 2 sections.

Or you can glue two boards together and cut a slight oval instead of a circle with the straight part of the oval equaling the kerf of the saw blade that you will cut them apart after the with after milling.

SG

That is impressive

Run them as 2 side by side so you cut a full diameter hole. Elongated for a saw kerf if necessary, then rip to width for two parts. No peaks, no chip out.

what rich said, router holes in full width board + thickness of blade then rip sucker in half

Thanks for the advice guys.

I will try the circle technique first as it seems like easiest

Use a hole saw as vs. one of those beam style circle cutters. Much cleaner cut and easier to do. Drill press of course.

Probably that's what you meant anyway.

BH Davis

600 half circles with a hole saw?

Ooops...........I must have missed the quantity somewhere along the way. CNC is the way to go but still cutting full circles and then ripping the boards in half.

You could onion skin the bottoms and then run through a wide belt sander bottom up to free up the centers as long as the sander isn't going to suck the centers up and into the belt mechanism.

A better way on the CNC might be to simply completely mill away the centers. A larger bit will speed it up on the bigger holes.

BH Davis

Good luck,
BH

depending on quantity, just run a hole saw down a center line then cut in half

We do these every now and then and I found this was the best way to cut them. 3/4 downshear bit, climb cut, no tearout, sand and finish. Used a 300 mm saw blade on the CNC (5 Axis) to cut out the finished parts but a table saw would do the same. I did not cut all the way through when cutting the bottle holes or the sawing out parts. Once the cnc was done cutting I took the board to the planer and took off the last 1/8 inch and had the finished parts.

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Perfect, thanks Krepco

FWIW worked like perfect, thanks for the tips

You're welcome.

cut the width of the board double what you need +the with of the saw blade and a pinch for sanding. cut out the circular holes and split the boards in half.