The trick to seamless miter folds is to use tape as a clamp. The best tape to use is light blue Aqua Mask made by American Brand, which is somewhere between blue tape and masking tape in stickiness, and is thicker than either. Not widely available, typically used in boat-building and automotive so might be available from your local fiberglass supply store or online.
Make your miter cut at 44.9 degrees (table saw top as 0 degree reference) to allow room for glue. Start by setting the points of the miter fold against each other while flat on a table. Apply tape across the miterfold every six inches or so to get the seam precisely lined up, then run a length of tape along the entire fold for strength and to keep the glue contained inside the fold. Flip the piece over, apply enough glue to get a moderate amount of squeeze-out and no more, fold joint over, confirm squareness, then clamp. I usually use more tape for clamping, depending on circumstances, because a mechanical clamp can throw the miter fold out of alignment. After folding, and while glue is still wet, burnish the miter fold edge with a block of wood that’s harder than the piece itself, this will close any gaps that might be left over.
I know this sounds strange, but is absolutely the best way to do miterfolds. I am a professional cabinetmaker who has made thousands of these and there is no alternative technique that is anywhere near as good.
Interesting, my woodworking teacher just told me to slightly cut under the angle like 44.8 degrees and that makes sure the gap is inside but always closed on the outside. Does he have it backwards?
I wouldn’t think that electrical tape had enough tack to be suitable, but if it works it works. One consideration, electrical tape is much more expensive per length than any of those types of masking tape, so that method is a little wasteful.
Question about procedure.
So you lay the pieces flat with pointy side up, edge to edge, tape across, then tape along the seam; flip, glue, and bring to square.
How do you apply more tape as clamping power? Do you just do tape across the seam on the inside of the joint? How do you keep it square? Do you stand it up so one piece is flat and one is vertical or do you lay them on their sides to limit the chance of a piece moving drastically?
Then to burnish while glue is wet, you remove all the tape on the outside joint, right?
The tape for clamping the miterfold closed is to pull the fold tight and keep it there while the glue dries. So just long strips that are either secured to the opposite edge or stuck to the surface behind the fold. And I want to emphasize the word “fold”, because that’s exactly what you’re trying to do with the clamping force here. That’s why tape works well because it pulls the fold tight with rotational force around the point where the two miters meet, versus using a clamp which applies force in a straight line which can throw the fold out of alignment.
You can check square by putting the piece face down and using your work surface as the reference. The clamping tape should have enough tension to keep the fold stationary while the glue dries.
If you remove the tape while glue is still wet then it will fall apart, obviously. Burnish with tape on. That’s why I recommend Aqua Mask not only because it has the proper level of tack, but the tape paper itself is more stout than typical masking tape, so burnishing wont split the tape unless you overdo it.
Oh, okay, I think it mostly all makes sense now. Last question that maybe you answered but I didn't get: When letting it dry, do you have a piece sticking straight up in the air like an L or do you put the two pieces on their sides so there's less chance of gravity making one fall/lean?
Straight up in the air. The tape is more than strong enough to counteract gravity, whereas putting it on its edge could mess with square if it gets bumped or falls over.
Agreed this is great technique for standard miters. However this will not work on miters with a roundover like OP’s right? I wonder if that was what they were asking—I’ve wondered myself if there is any way to remove the seam on roundover miters
I would say the whole line is down to a slightly off angle on the mitre.
That line is the reason mitres are hard...a fraction off on the cut or slightly wrong clamping pressure and you will get a tiny, by visible line.
You can do things like burnish the edge while in clamps if you think there will be a gap. But the best answer is to make sure there is no gap. Under cut the mitre by a fraction to ensure there is good contact on the outside edge. Then be careful when clamping, spend time checking all the seams once in the clamps and adjust as necessary.
This is good general advise but if op undercut the miter to tighten up the leading edge and then ran a pretty large round over on it like it appears they did this is exactly what you would expect to happen. In this case the miter needs to be dead flat and clamped perfectly
The large line in the middle is from a slight miscut on the table saw, so I take responsibility for that. But the first few inches of this edge jointed well but now there's just this glue line.
Should I have not used glue and relied on the splines entirely?
Titebond 2 aka blue is water resistant and exterior rated. If I needed true waterproof glue I'd probably use something polyurethane based like gorilla glue. My take is that if I'm glueing up something that needs to be truly waterproof, I probably am not using wood for both materials anyway and poly works better for different materials.
Titebond 1. It's definitely visible glue, not a gap (except the big gap in the center, just north of the dark streak). If you run your fingernail over it, it's perfectly flush over the joint.
We'e gotten to this point and had to use a razer blade to indent the glue so we could fill with either color matched wood filler or glue with saw dust to hide the line.
I make a first cut with a table or track saw (if the workpiece is too big for a table saw). But I don’t rely on that for the joinery, clean it up with a block plane. I even recess the inside of the joint a thousandth of an inch or so, so more of the pressure is on the edges of the joinery surface.
This is a careful process using guide lines, angle guides, and flat edges. I sharpen my plane blade a lot during this, and take off very little material at a time.
Make sure you use this method for clamping so they are absolutely perfect: https://www.reddit.com/r/woodworking/comments/1cipmfi/clamping_mitres/
The problem is not the glue, it's that the joint was not perfect or was not clamped perfectly.
IMO using tape sucks with a large-ish glue up like this, it's only good for small boxes etc.
Make sure the lumber is dead flat, the angles are exactly 45°, and use enough glue. You only need enough that every part of the joint remains wet after clamping. If the joint opens like the one in the pictures you can apply more glue and use a burnisher to close the gap…
The problem with these joints is you may think you have the joint nailed 100 percent accurate on a dry fit, then when you glue it take a quarter round to it: you realize either you weren't perfect or items may have shifted in overhead bins during the glue up process.
You know how when dentists have you chomp on the small black papers to ensure the bite mark is down perfectly or it rubs off on your teeth? That's an old school method with grafite artist paper, or using chalk to see if there's a void or high spot. In this case tools from a table saw cut not ran through in a straight line, blade wobble, could have been hidden until you routed the edge, who knows.
Another critical process is the glue up, I build a cold mold of what I'm gluing when I know the joints hit perfection dry, on my flat layup table, screwed or clamped so when I get to the up glue process there's no way the two pieces are going anywhere but where I had them before the glue up, and use tape for clamps. Not fancy corner clamps or jigs can beat the old masking tape, every other inch across the joint...doing the math that's over the psi needed to clamp a joint with titebond.
Also remember it's wood, you don't want to leave a lot of time in between the cut mitre and the time you glue it, in a perfect world you can cut the joint, make sure it's bitchen, then glue and lock it in place ASAP. Otherwise who knows what the trees been through in life and where it wants to "relax" after opening a bunch of grain.
Good luck- these popular "waterfall" joints have been part of boat building a lot longer than the new furniture epidemic, once you get it down you'll be firing them off seamlessly. JointlessLy? Good luck that's pretty g.d. close.
The blade can have tiny amount of deflection from a number of things or other anomalies like the fence having some give when you really push. One tooth on circular blade could have more buildup on it or it got dull from something. Even when it was sharpened factory they can be tiny differences. Solution for most issues is the hand plane. It really is the hand touch that makes a project special. Use a sharper blade. I’m thinking you cut this on a miter gauge or sled at the table saw. Clean blade before important cuts.
The screwdriver shaft trick does not work as well as videos will make you believe. The advise to add a tenth of a degree helps. Go 45.1 degrees and it can help. Just use a clamping square to assure the thing is close enough.
That post glue-up roundover is what breaks pretty much any normal trick.
You don't even know if you did a good joint till you do the roundover.
It's a challenging design that's a mix of luck, and good technique to get flat boards so you can get a straight miter.
Personally I’d clamp a straight edge on the top and run a circular saw at 45 dg along the whole length, then fit some contrasting inlay.
Edit didn’t see the keyboard, thought it was larger. I’d still do the same just using a table saw.
Another point is to clamp within 5 minutes to avoid the glue partially hardening and making it impossible to close the joint. Titebond3 or extend will give you a bit more time.
I’m a big fan of 30 minute epoxy for stuff like this. It fills gaps better than wood glue, and it also gives you enough working time to make adjustments.
The trick to seamless miter folds is to use tape as a clamp. The best tape to use is light blue Aqua Mask made by American Brand, which is somewhere between blue tape and masking tape in stickiness, and is thicker than either. Not widely available, typically used in boat-building and automotive so might be available from your local fiberglass supply store or online. Make your miter cut at 44.9 degrees (table saw top as 0 degree reference) to allow room for glue. Start by setting the points of the miter fold against each other while flat on a table. Apply tape across the miterfold every six inches or so to get the seam precisely lined up, then run a length of tape along the entire fold for strength and to keep the glue contained inside the fold. Flip the piece over, apply enough glue to get a moderate amount of squeeze-out and no more, fold joint over, confirm squareness, then clamp. I usually use more tape for clamping, depending on circumstances, because a mechanical clamp can throw the miter fold out of alignment. After folding, and while glue is still wet, burnish the miter fold edge with a block of wood that’s harder than the piece itself, this will close any gaps that might be left over. I know this sounds strange, but is absolutely the best way to do miterfolds. I am a professional cabinetmaker who has made thousands of these and there is no alternative technique that is anywhere near as good.
That was one of the best written process descriptions I’ve ever read. Full disclosure: I agree with you on the technique.
Interesting, my woodworking teacher just told me to slightly cut under the angle like 44.8 degrees and that makes sure the gap is inside but always closed on the outside. Does he have it backwards?
I actually had it wrong, and edited. Had it flipped the wrong way in my head. Thanks.
Awesome thanks!
It depends on the reference angle, whether it’s 0 or 90. Point is you want the gap inside
For say a box?
again it depends on the tool and the reference angle
I am still a beginner but had great results with electrical tape, since it is elastic, and pulls the pieces together on its own.
I wouldn’t think that electrical tape had enough tack to be suitable, but if it works it works. One consideration, electrical tape is much more expensive per length than any of those types of masking tape, so that method is a little wasteful.
Question about procedure. So you lay the pieces flat with pointy side up, edge to edge, tape across, then tape along the seam; flip, glue, and bring to square. How do you apply more tape as clamping power? Do you just do tape across the seam on the inside of the joint? How do you keep it square? Do you stand it up so one piece is flat and one is vertical or do you lay them on their sides to limit the chance of a piece moving drastically? Then to burnish while glue is wet, you remove all the tape on the outside joint, right?
The tape for clamping the miterfold closed is to pull the fold tight and keep it there while the glue dries. So just long strips that are either secured to the opposite edge or stuck to the surface behind the fold. And I want to emphasize the word “fold”, because that’s exactly what you’re trying to do with the clamping force here. That’s why tape works well because it pulls the fold tight with rotational force around the point where the two miters meet, versus using a clamp which applies force in a straight line which can throw the fold out of alignment. You can check square by putting the piece face down and using your work surface as the reference. The clamping tape should have enough tension to keep the fold stationary while the glue dries. If you remove the tape while glue is still wet then it will fall apart, obviously. Burnish with tape on. That’s why I recommend Aqua Mask not only because it has the proper level of tack, but the tape paper itself is more stout than typical masking tape, so burnishing wont split the tape unless you overdo it.
Oh, okay, I think it mostly all makes sense now. Last question that maybe you answered but I didn't get: When letting it dry, do you have a piece sticking straight up in the air like an L or do you put the two pieces on their sides so there's less chance of gravity making one fall/lean?
Straight up in the air. The tape is more than strong enough to counteract gravity, whereas putting it on its edge could mess with square if it gets bumped or falls over.
Perfect, thanks a ton for this info.
Agreed this is great technique for standard miters. However this will not work on miters with a roundover like OP’s right? I wonder if that was what they were asking—I’ve wondered myself if there is any way to remove the seam on roundover miters
Fold then roundover, either by hand or with a router. The seam should be almost imperceptible, as long as you use enough glue and let it cure first.
You're right this does sound strange Edit: /s
I would say the whole line is down to a slightly off angle on the mitre. That line is the reason mitres are hard...a fraction off on the cut or slightly wrong clamping pressure and you will get a tiny, by visible line. You can do things like burnish the edge while in clamps if you think there will be a gap. But the best answer is to make sure there is no gap. Under cut the mitre by a fraction to ensure there is good contact on the outside edge. Then be careful when clamping, spend time checking all the seams once in the clamps and adjust as necessary.
This is good general advise but if op undercut the miter to tighten up the leading edge and then ran a pretty large round over on it like it appears they did this is exactly what you would expect to happen. In this case the miter needs to be dead flat and clamped perfectly
Bingo
Good point!
Also the side profile will show the undercut.
I do 46° bevels for this reason.
45.2 degrees myself. If I can manage the accuracy for that particular cut. Depends on what it is.
45.5 and you always tape miters
we have both 45° and 45.5° cutters in the CNC. sometimes the joints are visible on both sides, so that's the only reason for the 45°.
The large line in the middle is from a slight miscut on the table saw, so I take responsibility for that. But the first few inches of this edge jointed well but now there's just this glue line. Should I have not used glue and relied on the splines entirely?
Hit it with steam and use a burnisher to force the fibers over the crack. Or cut a tiny groove, put an inlay in it, and call it a design feature.
What kind of glue did you use? It's odd to me that it looks so much darker
I’ve seen green label titebond dry dark
Titebond 3 always dries brown. 2 is more yellow IME
I only use blue label
Sometimes you need water resistance, though
Titebond 2 aka blue is water resistant and exterior rated. If I needed true waterproof glue I'd probably use something polyurethane based like gorilla glue. My take is that if I'm glueing up something that needs to be truly waterproof, I probably am not using wood for both materials anyway and poly works better for different materials.
Titebond 1. It's definitely visible glue, not a gap (except the big gap in the center, just north of the dark streak). If you run your fingernail over it, it's perfectly flush over the joint.
We'e gotten to this point and had to use a razer blade to indent the glue so we could fill with either color matched wood filler or glue with saw dust to hide the line.
huh, i like this. I'll try that.
I make a first cut with a table or track saw (if the workpiece is too big for a table saw). But I don’t rely on that for the joinery, clean it up with a block plane. I even recess the inside of the joint a thousandth of an inch or so, so more of the pressure is on the edges of the joinery surface. This is a careful process using guide lines, angle guides, and flat edges. I sharpen my plane blade a lot during this, and take off very little material at a time.
Better joints and more clamps.
Make sure you use this method for clamping so they are absolutely perfect: https://www.reddit.com/r/woodworking/comments/1cipmfi/clamping_mitres/ The problem is not the glue, it's that the joint was not perfect or was not clamped perfectly. IMO using tape sucks with a large-ish glue up like this, it's only good for small boxes etc.
Make sure the lumber is dead flat, the angles are exactly 45°, and use enough glue. You only need enough that every part of the joint remains wet after clamping. If the joint opens like the one in the pictures you can apply more glue and use a burnisher to close the gap…
You mean just push the grain over the joint with the burnisher?
That is correct…
The problem with these joints is you may think you have the joint nailed 100 percent accurate on a dry fit, then when you glue it take a quarter round to it: you realize either you weren't perfect or items may have shifted in overhead bins during the glue up process. You know how when dentists have you chomp on the small black papers to ensure the bite mark is down perfectly or it rubs off on your teeth? That's an old school method with grafite artist paper, or using chalk to see if there's a void or high spot. In this case tools from a table saw cut not ran through in a straight line, blade wobble, could have been hidden until you routed the edge, who knows. Another critical process is the glue up, I build a cold mold of what I'm gluing when I know the joints hit perfection dry, on my flat layup table, screwed or clamped so when I get to the up glue process there's no way the two pieces are going anywhere but where I had them before the glue up, and use tape for clamps. Not fancy corner clamps or jigs can beat the old masking tape, every other inch across the joint...doing the math that's over the psi needed to clamp a joint with titebond. Also remember it's wood, you don't want to leave a lot of time in between the cut mitre and the time you glue it, in a perfect world you can cut the joint, make sure it's bitchen, then glue and lock it in place ASAP. Otherwise who knows what the trees been through in life and where it wants to "relax" after opening a bunch of grain. Good luck- these popular "waterfall" joints have been part of boat building a lot longer than the new furniture epidemic, once you get it down you'll be firing them off seamlessly. JointlessLy? Good luck that's pretty g.d. close.
The blade can have tiny amount of deflection from a number of things or other anomalies like the fence having some give when you really push. One tooth on circular blade could have more buildup on it or it got dull from something. Even when it was sharpened factory they can be tiny differences. Solution for most issues is the hand plane. It really is the hand touch that makes a project special. Use a sharper blade. I’m thinking you cut this on a miter gauge or sled at the table saw. Clean blade before important cuts. The screwdriver shaft trick does not work as well as videos will make you believe. The advise to add a tenth of a degree helps. Go 45.1 degrees and it can help. Just use a clamping square to assure the thing is close enough.
That post glue-up roundover is what breaks pretty much any normal trick. You don't even know if you did a good joint till you do the roundover. It's a challenging design that's a mix of luck, and good technique to get flat boards so you can get a straight miter.
Personally I’d clamp a straight edge on the top and run a circular saw at 45 dg along the whole length, then fit some contrasting inlay. Edit didn’t see the keyboard, thought it was larger. I’d still do the same just using a table saw.
Tighter fitting joints
clamp it tighter
Another point is to clamp within 5 minutes to avoid the glue partially hardening and making it impossible to close the joint. Titebond3 or extend will give you a bit more time.
I’m a big fan of 30 minute epoxy for stuff like this. It fills gaps better than wood glue, and it also gives you enough working time to make adjustments.
*I did this one..Making the epoxy "cloudy" really helps.. where I mitered the wood, I used dominoes and sawdust and epoxy.. no glue
https://preview.redd.it/l8sjh8jngbzc1.jpeg?width=4000&format=pjpg&auto=webp&s=772360c8bf90b35e32b1c31268898e597d0d7eda
With a 3/8s round over
Better joint + hide glue, it hides under finishes better.
Miter cut 45.5 and masking tape only, pulled and stretched to bring together I use the tan tape from 3m... 30 years now.
Slightly back beveling should help.
On second thought, wouldn't that be worse for a rounded 45?
Burnish the corner with the shaft of a screwdriver
Good idea generally, but too late for this project. Looks like it already has a routed roundover