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Cutting miters accurately for a triangular table

1091 Views 10 Replies 7 Participants Last post by gdaveg, 9 mo ago

maxwellllll

Discussion Starter · 9 mo ago (Edited by Moderator)

I'm working out plans for building a triangular table per a friend's request. The top will be a "regular right triangle"-meaning the two sides at 90 degrees are the same length (a=20.5", b=20.5", c=29").

I'll be making it out of rift-sawn white oak ply, and I'd like to try adding a contrasting hardwood edge to it. I'm not a particularly seasoned woodworker (about 5 years of weekend warrioring), so I plan to do what I normally do: make a scale model first.

I know this is super basic stuff, but what I'm having a hard time thinking through is how I can be precise on the miter cuts for the hardwood trim. I just haven't had much need over the years to cut miters with precision. Sides a and b will each have one 45-deg end and one 22.5-deg end. Side c will have two 22.5-deg ends. The inside of the miter's lengths will need to match the dimensions of the plywood triangle's lengths. The outside of the miter's lengths will be those same lengths plus the width of the edge trim stock.

So what's the most effective way for me to get these cuts right and hit the lengths I need? I'm inclined to do it on the tablesaw, because I have that much more dialed in that my miter saw, and I inherently trust the accuracy of those TS cuts and angles from experience. Seems like I can use a stop block to get a and b to match up correctly, and then I'd probably try to sneak up on the final cut for side c to get it to mate up with a and b properly. Does that seem like the right idea, or am I "doing it wrong"?

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splintergroup

· #2 · 9 mo ago

Depending on you thoughts about any exposed end grain on the trim, personally I'd keep the long edge without any miter cuts. Each end of the short sides gets a 45.
You could even add the short sides to the top, then trim the long edge after these sides are in place. The long edge trim gets added and the ends (outside cuts) are done to get the desired look.

Benefits are perfectly closed joints and no work required to cut each piece to some exact length.

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1thumb

· #3 · 9 mo ago (Edited by Moderator)

Do shorts first. Line them up with a dummy piece for long side so you'll know miters will close. Install them. Then measure long to long and cut your long piece to match existing trim instead of short to short to match plywood.

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RichT

· #4 · 9 mo ago

Better account for wood movement when you attach the left piece of edging and the one on the hypotenuse. Also, your mitered corners are going to open up when the wood gains moisture, and/or separate from the core when it shrinks.

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bandit571

· #5 · 9 mo ago (Edited by Moderator)

Have never worried too much about a stick of wood shrinking along it's LENGTH…..but…

IF one wants to get fancy at those corners….Finger/ box joints work quite well…

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RichT

· #6 · 9 mo ago

Have never worried too much about a stick of wood shrinking along it s LENGTH…..but…

- bandit571

I didn't say the wood would move along its length. Read more carefully and you might understand that it's the wood movement of the core.

However that's moot since he's using plywood, so I should have read more carefully as well.

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maxwellllll

Discussion Starter · #7 · 9 mo ago

Depending on you thoughts about any exposed end grain on the trim, personally I d keep the long edge without any miter cuts. Each end of the short sides gets a 45. [ . . . ]

Do shorts first. Line them up with a dummy piece for long side so you'll know miters will close. Install them. Then measure long to long and cut your long piece to match existing trim instead of short to short to match plywood.

Both good options here. Thanks for the feedback! The "easy" one there (from @splintergroup ) might make some sense for this project. This is going to be fitting into a space in the room adjacent to a sectional, so much of the edge won't really be visible.

It's probably good to note: I was planning to radius the corners of the trim with a pattern bit, and I was also considering (more just to continuously add "learning opportunities" to my projects) adding splines at the corners.

Any thoughts on if either of these two additions (radius-ing and splining) a) are a good or bad idea, and b) would make one of the mitering approaches stand out as a better or worse idea . . . ?

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gdaveg

· #8 · 9 mo ago (Edited by Moderator)

Get some poplar and make strips the same width and thickness of your edge bandings. Tilt saw to desired angle and put stop blocks and sneak up on the final cuts. I like Splinter's idea too. The sides may not be exactly the same, so do trial cuts to match each side.

I sketched out how I would cut the triangles. If you want me to go through the steps let me know. Sketch below:

Cut 2 is not exactly the safest cut you can make as the side against the fence is exactly the same as the width of the cut. Have a helper guide the cut off side so it feeds the same on both sides of the blade.

Double back tape the 20" square to panel 2. Line up corners with edge of panel 2 so the saw blade is centered on corners. May take two people.

Handwriting Rectangle Font Schematic Parallel

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maxwellllll

Discussion Starter · #9 · 9 mo ago

Get some poplar and make strips the same width and thickness of your edge bandings. Tilt saw to desired angle and put stop blocks and sneak up on the final cuts. I like Splinter s idea too.

I sketched out how I would cut the triangles. If you want me to go through the steps let me know.

Wow! Very generous of you to take the time to sketch that out, gdaveg! It hadn't occurred to me to go the tape route, but that makes a ton of sense, and seems both safe and accurate-and I just grabbed a fresh roll of double stick tape earlier this week!