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I built my own small CNC router ( from a kit ) I'm going to be cutting some 1/4" plywood, basically just cutting shapes out of it, and I was wondering, what is the best router bit for simply making shaped cuts through plywood with as little router width as possible .. is there a specific bit for that?

  • I should mention I have a dewalt routher that takes a 1/4" shank – user379468 Nov 6 '15 at 17:11
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    It looks like a quick google search for "Plywood cutting router bit" returns about a quarter of a million hits. This leans very closely to a "Product recommendation" which are generally frowned upon here. I would however encourage you to look for one with a spiraled fluting, as this helps avoid tear-out. Also, check out the "Wood working" stack exchange – BrownRedHawk Nov 6 '15 at 17:22
  • 1/4" ply isn't very challenging, so any quality bit should do. A spiral up-cut bit is prone to damaging the face nearest the router; a spiral down-cut will damage the other side. (Apologies to @brownredhawk if he meant a different kind of spiral fluting.) If your cnc will plunge, then buy a plunging bit. For general recommendations on quality, Fine Woodworking (among others) will do occasional tests. You'll see the same names come up as good performers, although that usually goes hand in hand with price. – Aloysius Defenestrate Nov 7 '15 at 1:43
  • @AloysiusDefenestrate No worries, I was thinking that for some thin plywood, sometimes you can get quite the "fuzzy edge" on the thinner layers, depending on their orientation. If you didn't want to do a lot of sanding, sometime an up or down cutting flute can help, although at the expense of the opposite edge. – BrownRedHawk Nov 8 '15 at 19:21
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You need a spiral upcut, solid tungsten carbide cutter. Just make a vacuum skirt for the collet area of the router to remove dust and provide cooling.

Here is the one I use: http://www.amanatool.com/products/cnc-router-bits/spiral-compression-cnc-router-bits/solid-carbide-spiral-plunge-cnc-router-bits/46316-solid-carbide-spiral-plunge-1-4-dia-x-1-1-8-x-1-4-inch-shank-up-cut.html

One bit will cut about 800 linear feet flawlessly at 3/4" penetration (You have to get feed pressure and RPM right). After that quality declines linearly.

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I think that for what you're describing, a simple 1/4" shank straight bit is what you want. If you use the up-spiral type, it will clear sawdust better. I don't know if that will make a difference with your setup, you'd have to experiment with your CNC, test to see what speeds work best with which bits for different materials.

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YOU WANT A STRAIGHT BIT!! do not listen to people who copy paste "up cut bits make the chips come out better" they don't know what they are talking about.. with plywood up-cut bits causes surface tear not a clean cut. You should be using a vac to clear chips if you don't have a built in one use a shop vac+smallest attachment and hold it up near the bit when cutting.

Down cut- clean top and tear out on the bottom. up cut- clean bottom torn out top. compression- clean top and bottom rough middle straight- clean top bottom and middle

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