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Material is hard maple, though this happens a little bit with cherry and not at all with walnut.

I've been making plates with my router, and with almost 100% consistency I end up having to spend time heavily sanding these inside edges. I thought maybe it was due to the router bit being blunt, but this happens with freshly (and professionally) sharpened bits as well.

I run the router on the "4" setting (I guess approximately 22,000 rpm) with a 1 1/4 inch bowl cutting bit (1/2 shank on a 2 inch extender, though to anyone who thinks that may be a problem, I get the same issues without the extension on a smaller diameter bit). Material is removed about 1/16-1/8 at a time.

I'm fresh out of creative ideas for dealing with this and am quickly losing my hair here. One of the bigger issues is that due to this tear out, almost every plate is slightly different in diameter, and has sort of a 'wobble' around those areas where I have to sand more to remove the chop - for picky clients, I end up dealing with a lot of rejects.

tear out from router

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  • Excellent question with everything present for an accurate and precise answer. Welcome to WW.SE.
    – user5572
    Commented Sep 9, 2019 at 18:24

2 Answers 2

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I'm embarrassed to say that I guess I didn't really read enough articles on router bits.. and I was running it way too fast. Needed to slow the router down to around ~18k (speed ~2). So I ran out to the garage to try it out and.. the tear out isn't gone, but it's not nearly as bad. I have a feeling that if the bit I was using was a freshly sharpened one, it would have been even better. :sigh: Read your manuals, folks.

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    Been there, tore that out. Everyone goes done the hard lesson road at least once.
    – NothingToSeeHere
    Commented Sep 9, 2019 at 17:09
  • Good self-Answer. A couple of points are also worth mentioning. If you reduce the amount taken off each pass you always improve cut quality (1/8 is a lot when cutting against the grain) and simultaneously reduce the chance of burning as long as the feed rate isn't too low. This also extends bit life, maybe important for production work. And if the very last pass is very shallow, much less than 1/32, you can get an extraordinarily good surface. Because so little is removed in a skimming cut like this it's important that the passes that precede it don't tear out, so patience is required. [contd]
    – Graphus
    Commented Sep 10, 2019 at 7:04
  • Bit sharpness, with a lot of bits you can actually improve on the straight-from-the-factory edge and very likely also from a professional resharpen job. In addition to the obvious thing of using fine diamond plates (I'd suggest going to 1000 at least) SiC is just hard enough to abrade carbide. So standard wet/dry paper can be used to remove some material and it's worth taking the polish up a further notch and seeing if you get further improvement— as you're just polishing the flats this doesn't take long. Do all processes wet if you have the least concerns about the cobalt in the carbide dust.
    – Graphus
    Commented Sep 10, 2019 at 7:11
  • @Graphus - I like the "obvious thing" - you've lost me here. fine diamond plates? Sounds like something I'd find in minecraft. Can you elaborate or point me at an article? A quick google search left me just as stumped.
    – Stephen
    Commented Sep 10, 2019 at 21:11
  • Diamond sharpening plates, sometimes referred to as diamond 'stones' but they're plates of steel coated in diamond dust, adhered by a layer of nickel plating.
    – Graphus
    Commented Sep 12, 2019 at 6:16
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I see you have mostly mitigated the issue, but depending on how your jig works, you may want to consider climb cutting as well on the parts of the plate which tear out.

If you are unfamiliar with it, climb cutting is moving the router (or piece, if you are using a router table) the same direction as the bit is cutting, instead of moving against the bit. Normally it is discouraged, as it can be dangerous - the router bit can grab the piece more easily. However, if you are careful and take very small passes it can be good.

I use this approach when routing chamfers in acoustic guitar bodies in preparation for perfling and edging - for this, you always want to route in the direction that the wood grain is facing, so that the bit cuts out. In the case of plates, assuming you have the wood positioned such that the grain goes from 12:00 position to 6:00 position, you would want to climb cut from 12:00 backwards to 9:00, and then again from 3:00 to 6:00.

Whether or not you can do this of course depends on how you are cutting things. Do your research beforehand, and be sure to be safe!

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  • A good jig that firmly holds both the router and wood in place will do a lot to make climb cutting safer. Having good leverage on the moving piece also helps.
    – ratchet freak
    Commented Sep 9, 2019 at 14:11
  • After I get done this backlog of plates, I've got a jig design to help me accomplish just this. Man, would be a lot easier if my laser could actually cut through MDF.
    – Stephen
    Commented Sep 9, 2019 at 21:08

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