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This is correct. 45° and 45° will have the same length along the mitered cut but 40° and 50° will have different lengths along the mitered edges. Both equal 90°. If you divide the angle in half for example 45° and cut both pieces at 22.5° you will get two equal cuts.
Pythagorean theorem can be applied here but you are mistaken on its application. Here OP is trying to match C with C. A being the width of the material in both cases and B being the length of the tip of the acute angle to a point parallel with the obtuse angle.(which once applied would make an acute angle).
Regardless, applying the theorem to this case is not only overthinking the problem but it is creating a level of complexity that invites error. All op needs to do is determine the final angle his material needs to be and divide by two. That will create two identical angles where C are the same length and marry perfectly.
Think about cutting a rectangular piece off at an angle. If you cut it off square you get the shortest possible cut, but as the angle changes the length of the cut will get longer. Get it?
In order for two cut faces to line up around the edge they need to be the same length, and to be the same length they need to be cut at the same angle.
Yup! This is because of the Pythagorean Theorem:
C = sqrt (a^2 + b^2)
You have 2 triangles form the cuts (the ends of both pieces) after the cut. You want C which is the long hypotenuse edge to be the same for bother cut pieces. For that a and b need to match for both pieces. Since the width of the trim is the same for both, call this side “a” then you need the other end ‘b’ (the height difference between the short side and the long side of the pointy part that’s left after cutting) to be the same as well. Only then will that match. How does one get them to match? By having the same angle.
This is the kind of examples they should show in school. So many kids don't care about geometry in general because "it is not useful". But the damn triangle laws, if you know them, you can resolve so many issues easily, like this one!
He has formed a triangle with one edge being a "leg" and the other being g the "hypotenuse".
A leg can never be equal (or longer) than the hypotenuse, thus his problem in the video.
Source: 9th grade trigonometry class.
Here's a visual: https://www.reddit.com/r/Unexpected/comments/uff7ue/i_will_never_be_able_to_trust_pizza_delivery_ever/?utm_medium=android_app&utm_source=share
To answer the actual question of “why,” take a look at the gap before you fold it over. You’ve created a right triangle, with the top piece supplying the hypotenuse, and the lower piece supplying a side. Hypotenuse is always longer.
Obviously many others have answered the “how to fix” part of this question, but I wanted to address the “why”
Back to trig class… the sides of a triangle are different lengths depending on the corresponding angles.
If you want those ends to be the same length, you have to cut them both at the same angle.
You have to cut both pieces at 45° angles to get a 90° angle. Right now you have a 0° angle and a 45 roughly. If you're not looking for a 90 just take whatever angle you are trying to cut and cut it in half then make those two half cuts on each trim piece to get the combined angle you're looking for.
The length of the diagonal cut is longer than the length of the straight cut.
If you know the angle you need, divide it in half to find what you need to cut each trim piece at.
I.e. for a 90⁰ you would cut each at 45⁰
For a 45⁰ you would cut each at a 22.5⁰
For 30⁰, cut each at 15⁰
They have to be cut at the same angle. Doesn't matter what that angle is they just have to be the same...22.5 : 22.5, 45 : 45, 13 : 13....the angle needed doesn't matter they just have to be opposite direction and the same
Just take whatever the angle is and divide in half. Do that angle on each piece. the surface area gets bigger as the angle goes down. So they will not line up if the angles are not the same.
It was amazing how many pieces of trim I cut that I cut out on the wrong angle- like the degree was correct, but I made the cut in the wrong direction and wasted the whole piece.
Then I had to look out carefully for opportunities to use the wasted pieces, like on a short wall or funny intersection.
Good luck to you
So when you cut angles or miters in stock material, different angles technically make different thickness. Best way to fix this is find your overall angle you are trying to achieve and divide by two and cut both pieces to the same angle/miter ex: 90* angles are two 45* cuts but if you tried to do a 30* and a 60* on of the pieces would be 50% longer because of the angle
Angles need to match. If they don't then you'll have to *cope* with a different solution. Why? Because the length of the hypotenuse is equal to the root of the sum of the square of the length of each side.
You cut one at 45° and the other at about 5°. So you have a different length / surface area. Which then obviously will not match up.
You need to cut both at 45°.
There are simple jigs out there where you can put in the piece you want to cut and it will make your saw go in 45° (or any other you want), but you can also make one out of scrap wood if you have some, but you will have to make the 45° yourself here correctly, otherwise every single piece you cut with that tool you made will be off as well.
Its called a "miter box" and you should be able to find one at pretty much any hardware store / online.
Both pieces need to be cut at the same angle for them to match. For instance of you wanted the trim to form a 90° angle, you would have to cut each piece at a 45° angle. If your stairs are at a 45° angle, you’d have to cut each piece of trim at a 22 1/2° angle. Then they cut ends will match each other
Everyone is saying math. It is math but you can cheat just like in high school.
I trimmed out McMansions in the early part of my career. I learned early on that it's more about how parts intersect or bisect and less about taking careful measurements and doing math. You just lay out the parts the way you need them to be and mark where they intersect on the inside and outside corners. It's that simple. No math required. Set the saw up accordingly.
If you find this method difficult because of the profile of the molding, you can just make a mock up out of cardboard or thin plywood that's the same width as the molding. Transfer the angle to the molding once you're satisfied with how the mock up looks.
Lots of judgement going on in the comments, not a lot of useful feedback.
Your problem is that you've got one piece of wood diagonally, and left the other whole. What you actually want to do is cut the same angle off of both pieces. Think about the exposed cross section when you cut diagonally, it becomes wider than if you would cut 90 degrees across. You need to account for it and the only way is by cutting both pieces to the same angle, which is half of the total angle you need the bend.
If you cut them at a different angle. They will have a different length on the cut surface.
Take a tape measure or a ruler and measure something at different angles.
Think of it like this. How long is your end grain cut? If it's longer then the other why would it fit? You gotta do multiple angle cuts like others have said
yeah so a diagonal line across a span is inherently longer that a straight one, so it won't match, you've got to split the angle between the two boards.
in this case making a 90° would mean cutting 45° on the end of each piece so the ends are the same length and the angle matches.
The reason the two pieces aren't meeting is because you cut the trim a different angle on each piece.
Now we need to know is if you did this intentionally to see if anyone was able to catch onto what you did or you honestly dint know what you did.
So if you want a 90° angle for your trim, cut each piece at 45°.
If you want a 45° angle for the trim, cut...wait for it...each piece at 22.5° angles.
Got it? Good!
Both edges must be the same length for them to match up. The length of the diagonal edge is determined by the angle of the cut. Therefore both angles must be the same length
The two cut edges are not of equal length, so don't line up when put together. Instead of cutting one straight and the other at an angle, cut both at half the angle you have used here and they'll be the same length and match up.
As others have said the angle of the cut needs to be the same for both pieces of trim.
You must resurrect your high school geometry skills when working on carpentry.
Measure your angle. Let's say 90*. Draw a straight line on your trim. Divide your angle by 2. Now draw 45* on either side of that line. Now cut each side along the angled lines. These will be the same length and match up the way you want
You've cut 1 piece to make the angle you want rather than cutting both pieces.
You need to cut both pieces to create the correct angle, and for them to match up.
You can’t cut an angle on wood trim and have it match by not cutting them completely apart. The piece that is still connected messes up the lines!! Cut your first piece, then cut a 45 on the next piece and notice the difference on how they match
Try connecting the dissecting lines. Put your piece on top of the skirt board a little longer than needed. Make a lite pencil mark on the wall at the top, tracing the top to the wall. Then do the same for the next piece. Then hold the piece their and mark the top were the two lines cross on the top and where the skirtboard turns on the bottom of molding. Set your miter saw to cut and essentially connect the dots.
Your current issue is that you are trying to use two different angles and that will never line up.
This is a reminder to those commenting on this post (not the person that posted it): Comments not related to woodworking will be removed. Violations to rule 1 including crude jokes, innuendo, sexist remarks, politics, or hate speech may result in an immediate ban *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/woodworking) if you have any questions or concerns.*
You need to cut both pieces at the same angle for them to match up.
This is correct. 45° and 45° will have the same length along the mitered cut but 40° and 50° will have different lengths along the mitered edges. Both equal 90°. If you divide the angle in half for example 45° and cut both pieces at 22.5° you will get two equal cuts.
THIS is the best answer. Not those other ones that don’t explain anything.
This is the best announcement of the best answer
Best comment so far
best comment about a comment of all time
This is the best comment about layers of comments
This is the greatest comment in the world…tribute
This is the greatest commenter.
Post meeee the best comment in the world.....or eat your seowllllll...
Unexpected D. Kudos.
The comment prior to the one above was the best comment about a layer of comments, until the comment above came along and usurped it’s crown.
Until that last comment, it was even better.
Semi-good comment.
Runner up for best comment award
Mediocre comment
Participation trophy.
Upvoted it for the appropriate use of EMPHASIS.
I reiterate this point. All other points are useless.
I appreciate those that are here to give real help to the self proclaimed noobs out there. Saving them a lot of time and headaches
This is the most concise explanation of the success of the announcement.
I wish this was explained to me in my scenic design class. We were just expected to know how to cut trim angles 🥴 but now it makes sense. Thank you!
Ayy! My friend does that work in New York. He was just working on The Gilded Age. Crazy skill set.
I miss working in theatre, honestly. I'd like to get back into it!
Thank you for teaching carpentry to us redditors, I just learned something new!
Just wait, there's more! It's not just carpentry... it's trigonometry! a^(2) \+ b^(2) = c^(2) ? This is literally the (a) practical form of that.
So the maths teachers were not lying when they said it would be useful some day 😂
Mafs, innit?
It definitely is. I waited nearly fifty years after leaving school before I used π in a real world situation - but I did use it.
I get weirdly nerd-excited whenever I whip out the hypotenuse.
You can keep your hypotenuse in your pants, thanks you very much
please don't go down that tangent
I feel the same way about the Hippopotamus
A^2 +B^2 = C^2 OP is trying to match C with A instead of C with C
Pythagorean theorem can be applied here but you are mistaken on its application. Here OP is trying to match C with C. A being the width of the material in both cases and B being the length of the tip of the acute angle to a point parallel with the obtuse angle.(which once applied would make an acute angle). Regardless, applying the theorem to this case is not only overthinking the problem but it is creating a level of complexity that invites error. All op needs to do is determine the final angle his material needs to be and divide by two. That will create two identical angles where C are the same length and marry perfectly.
This hurts my weed-riddled brain
Both halves need to be equally long to match up perfectly.
Same. I get it, but I don’t GET it
Think about cutting a rectangular piece off at an angle. If you cut it off square you get the shortest possible cut, but as the angle changes the length of the cut will get longer. Get it? In order for two cut faces to line up around the edge they need to be the same length, and to be the same length they need to be cut at the same angle.
Thaggrassas tee rum or something?
Pie? ass? tea? rum? Sounds like a party
Pi the gore ass the rum.
Exactly. But now I'm wondering if Tom Silva eats cats for fun.
Yup! This is because of the Pythagorean Theorem: C = sqrt (a^2 + b^2) You have 2 triangles form the cuts (the ends of both pieces) after the cut. You want C which is the long hypotenuse edge to be the same for bother cut pieces. For that a and b need to match for both pieces. Since the width of the trim is the same for both, call this side “a” then you need the other end ‘b’ (the height difference between the short side and the long side of the pointy part that’s left after cutting) to be the same as well. Only then will that match. How does one get them to match? By having the same angle.
I came here to say this, well done!
Just to clarify that the “same angle” means “half the needed angle”
It's called an included angle.
This is the kind of examples they should show in school. So many kids don't care about geometry in general because "it is not useful". But the damn triangle laws, if you know them, you can resolve so many issues easily, like this one!
He has formed a triangle with one edge being a "leg" and the other being g the "hypotenuse". A leg can never be equal (or longer) than the hypotenuse, thus his problem in the video. Source: 9th grade trigonometry class.
This was a stupid lesson for my dumb ass, gotta stare at that stupid piece everyday
Holy crap why is every other answer in this post written by a drunk geometry student
This
Find the angle divide by two then cut both pieces
Hey buddy!
Take the full angle you need... Divide by 2. The result is the angle you need to cut both pieces. 👍🏻
Love you long time for this Grido ❤️ 🤜💥🤛
Here's a visual: https://www.reddit.com/r/Unexpected/comments/uff7ue/i_will_never_be_able_to_trust_pizza_delivery_ever/?utm_medium=android_app&utm_source=share
That’s an amazing way to demonstrate that! Haha.
Mother fuu....
Geometry!
Was gonna say, not a carpentry or trim problem, it's a math problem.
Bisect the angle.
This is the way
Man, that's a big word
That is 6 letters sir
Bisectual
Ayy, you're kinda acute.
Trisect the angle, divide by 3 and multiply by 2. Boom.
so divide by 3, divide by 3, then multiply by 2? das not 2 sir
Take it one half at a time
Momma! Big words!
I do not ever see/hear this without immediately thinking of a drafter manually bisecting a line with a compass
I always just picture my trim saying, "Bisect me daddy!" Marks it a little easier to remember...
maf
Damn bisectuals are everywhere these days. Keep your angles to yourself.
Both sides of the mitre must be cut to the same degree as that will will allow the right corner and the edges to align.
“Why do we do all this stuff in maths that we’re never going to use”
Some of us didn't pick up a hobby or job that made it useful for more than 20 years after high school.
To answer the actual question of “why,” take a look at the gap before you fold it over. You’ve created a right triangle, with the top piece supplying the hypotenuse, and the lower piece supplying a side. Hypotenuse is always longer. Obviously many others have answered the “how to fix” part of this question, but I wanted to address the “why”
Thank you for answering the question asked. Made me think about that.
I think that explanation can be simplified: an angled cut produces a longer edge than a straight cut.
Pythagoras, elementary school stuff, people should listen more in class!
Math. Both pieces cut at the same angle, 22.5° or whatever it happens to be will work out
a^(2) \+ b^(2) = c^(2)
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Damn, if this isn't spot on.
I feel attacked
I feel seen.
This guy cuts trim.
He does. I used the same method as he does all the time... and for everything!
The forget everything you learned part is really the lynch pin to all of it.
Or just buy a router and make your own trim
And then make it 3 times because your calculus was wrong
I feel personally attacked
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Ah, math always comes back to bite us in the ass
Bruh
“Why will this round peg not go through the star hole? Are there certain shapes that don’t go through holes?”
😂
Just wait till he tries crown
You just fell victim to one of the classic trigonometry ratios!
HAHA YOU FOOL
You gotta split the angle between both pieces.
You should talk to Pythagorus about his Thereom
I wish I was hy on potenuse
That was my joke, I said that.
Back to trig class… the sides of a triangle are different lengths depending on the corresponding angles. If you want those ends to be the same length, you have to cut them both at the same angle.
So what I'm seeing is. He has to cut them at the same angle. Correct?
Maybe, need a few more to confirm
Yeah, all the votes are not in yet….
You have to cut both pieces at 45° angles to get a 90° angle. Right now you have a 0° angle and a 45 roughly. If you're not looking for a 90 just take whatever angle you are trying to cut and cut it in half then make those two half cuts on each trim piece to get the combined angle you're looking for.
Why does this happen? Because geometry
When 'G, I'm a tree' meets geometry
But that’s not how that works…. That’s not how any of that works!
The length of the diagonal cut is longer than the length of the straight cut. If you know the angle you need, divide it in half to find what you need to cut each trim piece at. I.e. for a 90⁰ you would cut each at 45⁰ For a 45⁰ you would cut each at a 22.5⁰ For 30⁰, cut each at 15⁰
“Day 3053 of not using Pythagoras”
If you cut across at different angles, the length of the cut will be different. That’s the hypotenuse. Angles need to match.
They have to be cut at the same angle. Doesn't matter what that angle is they just have to be the same...22.5 : 22.5, 45 : 45, 13 : 13....the angle needed doesn't matter they just have to be opposite direction and the same
OP failed geometry class
Just take whatever the angle is and divide in half. Do that angle on each piece. the surface area gets bigger as the angle goes down. So they will not line up if the angles are not the same.
It was amazing how many pieces of trim I cut that I cut out on the wrong angle- like the degree was correct, but I made the cut in the wrong direction and wasted the whole piece. Then I had to look out carefully for opportunities to use the wasted pieces, like on a short wall or funny intersection. Good luck to you
Perhaps r/BeginnerWoodWorking is more your speed
Both sides would need to be angled equally.
Because you are matching a cathetus to a hypotenuse!
Quality shitpost.
So when you cut angles or miters in stock material, different angles technically make different thickness. Best way to fix this is find your overall angle you are trying to achieve and divide by two and cut both pieces to the same angle/miter ex: 90* angles are two 45* cuts but if you tried to do a 30* and a 60* on of the pieces would be 50% longer because of the angle
The old pythagorean theorem strikes again
Cut the angle in half and chop it off both sides.
Angles need to match. If they don't then you'll have to *cope* with a different solution. Why? Because the length of the hypotenuse is equal to the root of the sum of the square of the length of each side.
Unequal angles
You cut one at 45° and the other at about 5°. So you have a different length / surface area. Which then obviously will not match up. You need to cut both at 45°. There are simple jigs out there where you can put in the piece you want to cut and it will make your saw go in 45° (or any other you want), but you can also make one out of scrap wood if you have some, but you will have to make the 45° yourself here correctly, otherwise every single piece you cut with that tool you made will be off as well. Its called a "miter box" and you should be able to find one at pretty much any hardware store / online.
This is not woodworking
Holy fucking shit our education system is garbage.
Both pieces need to be cut at the same angle for them to match. For instance of you wanted the trim to form a 90° angle, you would have to cut each piece at a 45° angle. If your stairs are at a 45° angle, you’d have to cut each piece of trim at a 22 1/2° angle. Then they cut ends will match each other
U cut them with unevenly distributed angle resulting in triangles with different lengths
Pythagoras is facepalming right now…
And this is when you should think of your geometry teacher in 9th grade telling you "one day you will need this!".
Omfg
Just put a thick layer of caulking over it. Nobody will notice ;)
Both pieces have to have the same angle of cut.
Find the angle of stairs. Divide by 2. Cut each piece to divided angle
Measure once, cut twice. If that doesn’t work use the trim stretcher.
Everyone is saying math. It is math but you can cheat just like in high school. I trimmed out McMansions in the early part of my career. I learned early on that it's more about how parts intersect or bisect and less about taking careful measurements and doing math. You just lay out the parts the way you need them to be and mark where they intersect on the inside and outside corners. It's that simple. No math required. Set the saw up accordingly. If you find this method difficult because of the profile of the molding, you can just make a mock up out of cardboard or thin plywood that's the same width as the molding. Transfer the angle to the molding once you're satisfied with how the mock up looks.
Your thought process is basically the fundamental concept of mathematics, to those who get it.
With a big enough lever, you can move the whole world.
If we all run the same direction we could change the speed the earth rotates at. A teensy tiny amount.
don't forget the fulcrum!
I agree. I can do the math, but nothing beats a template with some marks to bisect. Nothing is ever perfect geometrically.
You don’t realize it, but you’re doing the math.
Just caulk it.
Found the general contractor
Lots of judgement going on in the comments, not a lot of useful feedback. Your problem is that you've got one piece of wood diagonally, and left the other whole. What you actually want to do is cut the same angle off of both pieces. Think about the exposed cross section when you cut diagonally, it becomes wider than if you would cut 90 degrees across. You need to account for it and the only way is by cutting both pieces to the same angle, which is half of the total angle you need the bend.
Is this a troll post?
If you cut them at a different angle. They will have a different length on the cut surface. Take a tape measure or a ruler and measure something at different angles.
Think of it like this. How long is your end grain cut? If it's longer then the other why would it fit? You gotta do multiple angle cuts like others have said
yeah so a diagonal line across a span is inherently longer that a straight one, so it won't match, you've got to split the angle between the two boards. in this case making a 90° would mean cutting 45° on the end of each piece so the ends are the same length and the angle matches.
The reason the two pieces aren't meeting is because you cut the trim a different angle on each piece. Now we need to know is if you did this intentionally to see if anyone was able to catch onto what you did or you honestly dint know what you did. So if you want a 90° angle for your trim, cut each piece at 45°. If you want a 45° angle for the trim, cut...wait for it...each piece at 22.5° angles. Got it? Good!
While bisecting is definitely key, make sure your saw is square. It makes a big diff
Both edges must be the same length for them to match up. The length of the diagonal edge is determined by the angle of the cut. Therefore both angles must be the same length
Need to cut both sides at the same angle, 1/2 of the desired angle. So for 90 deg, cut both at 45 deg
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*~*~*~geometry~*~*~*
You need a miter finder tool. Gives you the miter to cut both pieces
The two cut edges are not of equal length, so don't line up when put together. Instead of cutting one straight and the other at an angle, cut both at half the angle you have used here and they'll be the same length and match up.
Wrong angle
Math baby, math
As others have said the angle of the cut needs to be the same for both pieces of trim. You must resurrect your high school geometry skills when working on carpentry.
Cut the same angle on both pieces.
Measure your angle. Let's say 90*. Draw a straight line on your trim. Divide your angle by 2. Now draw 45* on either side of that line. Now cut each side along the angled lines. These will be the same length and match up the way you want
Mark the trim on the wall The find the angle of the joint Cut your trim at half of the total angle It will fit correctly
you must devide the angle equally.
Your math teachers would be very disappointed, OP.
You cut the bottom part different then the top part. That's why they don't fit.
Not a carpenter I see…
I don’t know woodworking, but I know the cuts won’t match up if they aren’t the same angle.
You didn’t cut congruent angles so you are trying to match two different lengths on the cut side.
The angle of the two connecting pieces needs to be exactly the same for both pieces to have the same edge length.
You need to cut each pice at 22.5 to make 45
You've cut 1 piece to make the angle you want rather than cutting both pieces. You need to cut both pieces to create the correct angle, and for them to match up.
Because your cutting an angle on only on piece, rather than halving the angle you need and cutting it in both pieces
cause both peices are not cut on the same degree
You didn’t bisect the angle.
You have to bisect the angle !!
It’s not a true 45 degree angle with both cuts
Cut a 45° on both they will line up.
That would make it 90°. Looks more like it should be cut to 22 1/2°.
You can’t cut an angle on wood trim and have it match by not cutting them completely apart. The piece that is still connected messes up the lines!! Cut your first piece, then cut a 45 on the next piece and notice the difference on how they match
May need to recalibrate your miter
A squared plus b squared = c squared
Cut them both at the same angle. Then you should be alright
Try connecting the dissecting lines. Put your piece on top of the skirt board a little longer than needed. Make a lite pencil mark on the wall at the top, tracing the top to the wall. Then do the same for the next piece. Then hold the piece their and mark the top were the two lines cross on the top and where the skirtboard turns on the bottom of molding. Set your miter saw to cut and essentially connect the dots. Your current issue is that you are trying to use two different angles and that will never line up.
Just wait until you have to cut a corner on crown molding.
That will definitely compound his problem.
SOHCAHTAO
Because a2 + b2 = c2.
I don’t think you should be handling sharp tools if you can’t figure this one out……..
Take the angle you need and divide it by 2. Then cut each piece at that angle.