Router plunge / cut depth for ½" BB ply?

Discussion in 'Shock Brother's DIY Amps' started by King Fan, Jul 25, 2021.

  1. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    I hope this is my best place to ask cabinet woodworking questions? For a baffle, I got some nice (B/BB) ½" baltic birch plywood from Woodcraft, and a ¼" double-flute plunge bit from Freud, and I have a circle cut attachment on my variable-speed, 1.5 HP router.

    But searching the web and YouTube, I see all sorts of suggestions for depth-of-cut, from 2mm up to 8 mm -- someone was even cutting ½" in a single pass. I realize it depends on RPM and cut rate, but I'm kinda wondering what experienced builders here suggest.
     
  2. Frodebro

    Frodebro Doctor of Teleocity Ad Free Member

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    I generally don't go much deeper than about 1/4" per pass, regardless of the size of the bit.
     
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  3. tele_savales

    tele_savales Tele-Afflicted Platinum Supporter

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    I've used my super cheap amazon-bought WEN dremel-type tool w a straight cutter and a $15 circle cutter jig and did a 12" hole all the way thru in one pass in 13mm ply. It was really dangerous.
     
  4. tele_savales

    tele_savales Tele-Afflicted Platinum Supporter

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    It worked tho! 1C44B024-3860-4B6F-AC91-B793E407512F.jpeg 4E9389F9-10F0-4FC8-9757-41549E879D07.jpeg
     
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  5. oldunc

    oldunc Tele-Afflicted

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    Yeah, 1/4" would probably be a good standard, though certainly not written in stone. I might start with a very shallow first pass just to assure a clean cut of the top veneer. If you're planning to cut out a circle you need to secure both parts of the piece carefully so that when your circle comes free the offcut doesn't get caught in the cutter; that can get kind of messy and dangerous.
     
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  6. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    <lolol> So that's a "what *not* to do, but it worked" answer? :):):)
     
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  7. Frodebro

    Frodebro Doctor of Teleocity Ad Free Member

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    I guess it really depends on whether the sight of your own blood makes you queasy or not...
     
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  8. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    I was gonna clamp the square stock, but hadn't thought about the "donut hole" piece.
     
  9. Frodebro

    Frodebro Doctor of Teleocity Ad Free Member

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    The "donut hole" is where the pivot point is, and what the router is anchored to. You really don't want it to move around...
     
  10. tele_savales

    tele_savales Tele-Afflicted Platinum Supporter

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    Pretty much. I think once I started my options seems to be burning the motor out on the tool or snapping the bit, and I had an extra bit. So I forced it.
     
  11. tele_savales

    tele_savales Tele-Afflicted Platinum Supporter

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    I didn’t find the waste circle to be an issue once it cut loose, but if you’re worried you could flush screw it down into your work table.
     
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  12. andrewRneumann

    andrewRneumann Tele-Holic

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    I’ve always cut the speaker hole with a jig saw. I’ve free handed and used a circle jig, both with excellent results. And I never feared for my life or worried about slipping and messing something up.

    I never thought of using a router. Is there an advantage to it?
     
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  13. tele_savales

    tele_savales Tele-Afflicted Platinum Supporter

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    10x faster and cleaner once you build or buy a jig and get your technique down.
     
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  14. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    I have tried several methods ending with good results.

    My go to method now: I have a pattern made of MDF and use a router bit with a bearing. It is like cutting a body. I trace the circle on the baffle. Cut near the tracing with a jig saw. Clamp the pattern to the baffle and use the router to make the finished hole. Resting the bearing against the pattern. I find it to be quicker and less likely to screw up. The router bits are not used as much so they stay sharp longer. Areas of the baffle more prone to tear out can have several passes with the router to alleviate that problem.

    I usually cut the baffle rectangular dimensions after cutting the speaker hole.
     
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  15. telepraise

    telepraise Tele-Afflicted

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    I only use solid carbide spiral bits for that kind of work. Even then, I only go 1/8" at a pass. There's no hurry.
     
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  16. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Good point. I guess each pass might add a few seconds of work. Oh, plus the seconds it takes to advance the plunge stop. Who knows, it might add up to several minutes. :)
     
  17. oldunc

    oldunc Tele-Afflicted

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    There are trammel point circle cutters that extend out to about 8" and hole saws at least to 6", but they really require a drill press. Of course if you're going to do several cuts, you can make a simple pattern and use pattern bits or, if you want to vary sizes a bit, template guides and straight bits.
     
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  18. BigDaddy23

    BigDaddy23 Tele-Holic

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    As others have mentioned above, it's easier to do it in a couple of passes with the trammel jig (I go in 3mm / 1/8" increments with my router as that's what the depth stop adjuster indexes at). That way when you get to the last bit that frees the 'circle' you can sneak up on it and control it nicely. I do this after I have fitted the grill cloth edge strips and turn the baffle board so it is face down. This way, the furthest the 'circle' and router can ever drop when it frees up is the thickness of the edge strips....not that you should let it drop...anticipate and control it! You will generally have a little bit to clean up by hand with a file where it separates.
     
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  19. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    I was going to cut the circle with my handheld jigsaw on a homemade 'radial sled' circle jig before I found so many YouTubes of cutting a circle with a router (including many on DIY jigs). And *then* I realized my Makita's edge guide converts to a circle jig. Well, duh. But I've never routed plywood before, and that's when YouTube and woodworking sites got confusing. You all helped. And now I know the waste chunk needs stabilization, too.

    Sure, I can overthink things. :) But overthinking is like whiskey. As Mark Twain said, "Too much is just enough."
     
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  20. oldunc

    oldunc Tele-Afflicted

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    This is especially true of power tools and especiallier of routers- if something goes wrong it usually happens WAY too fast for you to react; you need to think out your entire process before you turn anything on.
     
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