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I've got a project coming up that involves a lot of medium-small holes in several 4x8 sheets of 5/8ths baltic birch veneer. (I don't have the plans in front of me, but I recall that the holes are about 1 inch nominal or a little larger.) I think I have plan for making the holes: careful marking out of a grid, and then lots of forstner cuts with a jig. I'll have a sacrificial sheet of cheaper plywood underneath to minimize tear-out.

The holes are for dowels which, ideally, will slide in with a pretty tight interference fit. To make this slide easier (the idea is that the dowels can be moved) I'm thinking about chamfering the holes. I think this will look nicer, too.

I saw on a YouTube video someone using what looks like a dedicated tool for this purpose, but I can't quite tell what it is. Maybe a small router, but I have no idea what tool would be mounted in it. I'm pretty sure I don't want to do this with my router, as I'm certain any bit I can get for that will start to climb-cut, and then there's me with fewer fingers again.

I found this older question that gets to the heart of what I want to do: clean up the internal top edges of cuts in decent quality plywood, but in my case I'm hoping for a mechanised solution for multiple smaller diameter holes for ease and consistency.

Does anyone have any good ideas for light chamfering the facing edges of lots of medium diameter holes in baltic birch veneer?

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  • Hmm. Looks like the internets will give you better results if you search for "bench dog chamfering".
    – user5572
    Commented Apr 21, 2020 at 1:16
  • I take it these holes are too big for a basic countersink bit?
    – Gern Blanston
    Commented Apr 21, 2020 at 2:40
  • This doesn't speak to your question, but I know of someone that had a similar project to yours (drill lots of holes accurately in sheet goods). He found a local cad/cam shop that could do the work for way less than it would cost him. Maybe something to ponder...
    – Aloysius Defenestrate
    Commented Apr 21, 2020 at 13:02
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    @AloysiusDefenestrate that's a good idea, but right now I have more time than money, and trying to sort out getting three sheets to a CNC place in These Trying Times sounds like I'd rather stay home and make hundreds of holes by myself. About half-way through sheet #1 I may regret this decision.
    – user5572
    Commented Apr 21, 2020 at 15:01
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    @GernBlanston yeah, I'm going for at least one side of the cut really nice. So careful cutting with expensive forstners is probably best. I can chamfer (or not) as a second pass. I'm ok with the extra work, frankly.
    – user5572
    Commented Apr 21, 2020 at 21:52

2 Answers 2

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The tool in the video is a "trim router". Basically exactly the same as a a regular router, but smaller and lighter. Less power means they can't remove much material on each pass, but the lighter weight gives the user much more control. They're easier to use.

Looks like a "roundover" bit to me. A chamfer bit would work fine though personally I think rounded will look nicer and be more durable (chamfered edges tend to chip or dent).

I wouldn't use the "plunge" feature in a router for a job like this. Lock it into the correct depth with test cuts on scrap timber. The less things that can move the better. Make sure the work piece is clamped to the table so the only thing that can move is the tool which I'd move nice and slowly (not too slow or you'll create excessive heat).

How thin is the outer veneer on your plywood? Often the outer layer is nearly as thin as a sheet of paper which might not produce good results.

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  • Nice tip on "roundover". This'll help me find the tool I want. I'm about to spring for a compact router, and even if I get a plunge kit I agree not ideal for this use. This is very good quality veneer, and the internets indicate that taking off a 16th or so should give me decent results. But a test cut will prove that for sure.
    – user5572
    Commented Apr 21, 2020 at 14:57
  • Actually, I think my confusion is over the tool in the video, which appears to have a bearing that fits the hole, and then the tool cuts the chamfer at once. But all the chamfer or roundover bits I see have 3/8 or similar bearings. I think you are suggesting I use one of these bits in a smaller router, and then set the depth so the bearing actually runs around the inside of the hole in a little circle. This way I can avoid climb-cutting and get the depth I want consistently. And I can buy a more generally useful router and set of profile tools for other jobs.
    – user5572
    Commented Apr 21, 2020 at 19:50
  • Your understanding of the 3/8" chamfer bit/light router is spot on. With that tiny an amount of cutter exposed, climb cutting really isn't apt to be troublesome -- in fact, if your veneer is prone to chipping out, you might use a climb cut to your advantage. IMHO, you are unlikely to regret having more routers in your world.
    – Aloysius Defenestrate
    Commented Apr 21, 2020 at 20:30
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Well, it looks like (surprise!) what I want is a plunge (or plunge-by-hand) router with a chamfering tool installed. In this example I found it's a trim or compact router.

The key was to search for info on people building benches and needing to chamfer bench dog holes.

I'm not keen on using my hard-start Craftsman non-plunge router for this. I mean, I could get a plunge accessory (maybe) but this looks like I ought to part with some money for a compact router to save some time. I may have another project coming up that'll be easier with a compact router, anyway.

Even as much as I like the hand "bench dog hole chamfering tool" I see come up, I'm not that interested in getting a single-use tool (and having to have a set of them for different diameters) or putting my wrists through all that work.

Looks like I have to do some research on safely using 1/4in chamfer bits in holes. I bet I could even find a tool to cut and chamfer the holes in one go.

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