My first post, and (this much is probably obvious) I am not a woodworker. But I do aspire to some woodworking skills!
Here is my question: I’m making a box of 3/4″ baltic birch plywood (finnish ply, multi-ply, etc) with a phenolic coating. At the corners the ply sheets meet at a mitre joint as shown at the left of the image below, and they are joined by loose tenons (not shown).
What I’d like is shown at the far right in the image: a chamfered edge that has a little rounding in the transitions.
So how would one go about constructing this? I can easily build the scenario in the center image by beveling the ply before joining. But a good clean way to get the smooth transitions I do not know. (Though I suspect it involves routing!).
Thanks for any and all advice!
Replies
There are quite a few ways to get the corner you want. In all of them, I'd assemble the box with just the mitered corners first. A low tech way would be to use a file, rasp and/or sandpaper. Low angle block planes will also cut the corners. A router with a 45° chamfer bit is a good choice if you have a router. You should plan on removing most of the corner with one cut and leave a 1/32" for a final clean up pass. It's often a good idea to have a back up piece of wood both on the start and finish, particularly with hand routing. This will keep the ends from blowing out and keep you from accidentally going around the corner. After the corners are chamfered, the easiest way is just to shape the rounded edges by hand. Again a file, like an 8" mill bastard, would work well on the phenolic. A sanding block is also good and not very expensive, just a little more work.
Thanks for the reply. I worry that any but the lightest of sandpapering will make the edge of the phenolic a little rough (this along the length of the edge which goes into/outof the page in the images above). I'd like to retain the machined look as much as possible.OK, so route a rough pass or two from both sides, then final pass. And extend the work, that's a great idea, thanks. I'm just about to learn how to use a router, so I'll test this whole idea on a few mockups first. I'll post an image...
Good advice from the hammer...........
You could also cut your corners with a table saw/mitre guage, if you have one, and clean up the cut edge with a sanding block.
Whichever method you use, take care not to cut into your loose tenons.
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"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
You can rabbett outt the corner and fill it with quarter round (or any hardwood shaped to round the transition). Sanding out the edges of a plywood miter will reveal the veneers in the plywood as a series of stripes down the edge.
Also, I don't know how you set up your tenons, but a miter joint in plywood is pretty weak. It's good to give more support to it. I tend to use a spline down the length, but tenonss, if they are sized properly, will also do the trick.
How thick is the phenolic coating? Unless it's thicker than the "good" wood veneer on most plywoods, your chamfer may expose the substrate and wreck your joint.
I seldom use mitered joints in plywood because of strength issues, but when I do, I just lightly burnish the edges with a metal rod to slightly crush the veneer and eliminate the sharp edges.
Make up some practice joints and see what will work best for you.
The phenolic is very, very thin: it's integral with the multi=ply, and semi-transparent due to its thinness."Expose the substrate": do you mean the adhesive that attaches the phenolic to the ply?I think the chamfering of the edge should take care of the sharpness
you are talking about: there will be no sharp edge where the two pieces
join, that's for sure.I hope I'm understanding you correctly.(And replying to another post here: yes, the veneers in the ply will be exposed, but that's by design in this case.)Thanks everyone for your help, I'll post a picture as soon as I build a few tests...
If the plywood veneers are supposed to show, then disregard my suggestion. I spend quite a bit of time and effort trying to not have the plys show - lol.
Hah, I'm just learning at the moment...after I get it to do what I want with the veneers showing, I will try the more advanced version and hide them. In this particular case the veneers will look "apropriate"...
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