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I'd like to make some nice looking speaker boxes. The only material I have access to is melamine MDF. I don't have a table saw, so I get it cut at the store.

I want to bevel the edges so the corners will be at 45 degres (internal, so I can glue them) (I'll also have bracing inside so the corner glue won't be all of the support).

What would be the best way to get 45 degree corners? I have a circular saw and a router. The problem with the circular saw is that I don't have tracks for it so I'll need to be creative (also of course finding the exact 45 deg position).

The problem with the router is that 45 deg bits with 1" depth of cut (for 3/4" MDF) are rare and expensive. Or at least I haven't been able to find them

Also, I don't know if a beveling bit will chip the melamin. There are specific saws for circular saws to cut melamin MDF, so I suppose they will leave a clean cut.

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  • Hi, welcome to Woodworking. FFR please don't ask "What is the best way to do XXXX?" questions, because inevitably this leads to opinion-based Answers (as you're just about to see, since my Answer will be to use the router LOL).
    – Graphus
    Commented Jul 23, 2023 at 22:43

2 Answers 2

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I'd use the circular saw. A track is nice to have, but not necessary. You can get a similar effect by clamping a guide to the work piece, and sliding the saw along that. The guide can be anything long and straight with a smooth edge.

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  • I have some leftover 60mm extruded alu tubing which i think would work great. Is there a technique for cutting in a bevel? I imagine the teeth of the blade should bite "into" the melamine going down, while the opposite side of the cut will probably "blow out" and drag the melamine? or is this not a concern? the blade is 60 teeth for a 185mm saw. it says it makes "clean cuts" on melamin MDF. Makita D-61466
    – hjf
    Commented Jul 23, 2023 at 17:09
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    Your finish surface should be on the bottom, with the saw riding on what will become the interior of the box. Commented Jul 23, 2023 at 21:22
  • Many people are shocked to find that a "track saw" is a fairly recent invention (last 10 years or so), yet people have been making straight cuts with circular saws for decades before that. If you do want a track saw (and they are nice to have), do a web search for "homemade track saw". I followed the instructions in a This Old House video and have been very happy with the results. Almost lets you make a cut with your eyes closed!
    – FreeMan
    Commented Aug 10, 2023 at 16:40
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For cleanliness of cut, safety (not for you, for the workpieces) and accuracy I would do this using the router.

This isn't a freehand operation, it's something for the router table but before you baulk at that if you don't already have a router table, as outlined a number of times previously here, the most rudimentary router table you can imagine would suffice — that's a piece of MDF/plywood/chipboard with a hole drilled through it, clamped to the edge of a table or workbench. If you prefer you could build a super-simple tabletop router table, for which there are now numerous plans and how-to videos.

The problem with the router is that 45 deg bits with 1" depth of cut (for 3/4" MDF) are rare and expensive. Or at least I haven't been able to find them

I'm sure there are affordable options now1 but I'm going to recommend a different route anyway. You can sidestep the issue of finding a suitable 45° chamfering bit by using a straight-cutting bit, which of course you'll have much more use for down the line.

All that's needed in addition to the above is a simple jig. Such a jig can be a single-afternoon project, only requiring scraps of ply/MDF and some hardware.

Caveat
Regardless of the method you choose to use, you're going to have the devil of a time getting the result you're hoping for here, as every edge will have to be basically perfect. Remember, just one errant chip along any visible edge and the flawless look is ruined.

I would much rather use straight MDF (ideally a superior grade with higher density, but that's not essential) and then prime and paint it to a high standard, which isn't rocket surgery :-) This also means any chipping or roughness along any edge, even the most visible, becomes a non-issue..... which of course makes the top of the speakers a lot easier.

Simply using a small roller you can reliably2 achieve a very professional result which closely mimics a spraygun finish, using any decent enamel paint. And if you wanted to you could go further and achieve an automotive-level finish with more work and $$.


1 Just go straight to a Chinese vendor and sidestep any of the conventional online storefronts, which are mostly selling the same or very similar bits with a large markup.

2 It is possible to do this with rattlecan paints, but much, much harder to ensure a good result even with prior experience.

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    Lots of merit to the “use mdf, not melamine face”. A melamine miter (done right) will be scary sharp, and trying to knock it down with sandpaper will show a dark line. Commented Jul 24, 2023 at 1:42
  • i've made miter joints on 9mm MDF with the router bit I have and they came out just beautiful. painted, actually, with water based enamel. but this project is for subwoofers for a living room where they should match the existing "black wood grain" speakers already in the room, so paint isn't an option. i thought maybe veneer but it's almost impossible to find here (Argentina) and a 2.4m roll, 30cm wide, costs the same as half a 1.83 x 2.6m melamin MDF board........ that said, i think "rough cut" at an angle with the table saw and finishing it with a router bit would save a lot of wear and dust
    – hjf
    Commented Jul 24, 2023 at 4:22
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    btw they sell very inexpensive, "thick" textured paint for speakers which looks very nice for "rough use" like cars, or even professional speakers that you need to throw into a truck.
    – hjf
    Commented Jul 24, 2023 at 4:23
  • "btw they sell very inexpensive, "thick" textured paint for speakers" Good to know, thanks. This might be something similar to 'bed liner' paints, for the loading beds of pickup trucks. The stuff is famously strong and resilient!
    – Graphus
    Commented Jul 24, 2023 at 5:01
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    ...You don't want to risk scratching the faces so if you soften the corners with abrasive I'd highly recommend backing the paper with a hard block (just a small offcut of anything) so that there's no chance it can conform to the surface a rub both adjacent faces. If you had a block plane I would recommend planing along the edges as an alternative for making the very tiny chamfers. Either way, be sure to work away from all corners as laminate can lift and flake otherwise if you run off the edge.
    – Graphus
    Commented Jul 24, 2023 at 19:27

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