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Need Help/Input on Finding Proper Angles

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Forum topic by JK0702 posted 06-25-2015 10:41 PM 1085 views 0 times favorited 28 replies Add to Favorites Watch
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JK0702

131 posts in 1591 days


06-25-2015 10:41 PM

I could use some help on how to find the proper angle to cut support pieces for my table project. This has always given me trouble. It comes up when installing diagonal support pieces on a picnic table, picnic bench, or any project with diagonal support pieces. In this case, I am running diagonal supports between two horizontal surfaces. The cuts are on opposite sides of the support piece, meaning the angle cut is on the top of the high end of the support and on the bottom side of the low end of the support.

I can’t just lay the diagonal piece against the horizontal pieces and make a pencil mark to show the angle. My angle cuts never seem to be right on the money, as I’m always just guessing. Can any of you guys give me a simple method to figure this out? I know the Pythagorean theorem will tell me the length of the support piece, but how do I find the angle? I believe that the two angles should be the same because they are corresponding angles, but it’s been a long time since math class. Please help, this is bugging the heck out of me. Any youtube videos would be great.

Thanks,
John

-- John - Huntington Beach, CA --- Growth occurs when we get out of our comfort zone.


28 replies so far

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pjones46

986 posts in 2102 days


#1 posted 06-26-2015 01:30 AM

A picture would help, I really can’t visualize what you are trying to do.

-- Respectfully, Paul

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bondogaposis

4020 posts in 1811 days


#2 posted 06-26-2015 02:51 AM

45° works for me in most cases.

-- Bondo Gaposis

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waho6o9

7166 posts in 2036 days


#3 posted 06-26-2015 03:34 AM

Festool angle divider ^

Or

Stanley angle divider

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jerryminer

528 posts in 901 days


#4 posted 06-26-2015 03:37 AM

It’s trigonometry. I don’t really know trig, but my scientific calculator does.

First, figure out your rise and run (Rise= vertical dimension. Run = horizontal dimension)

Divide rise by run : rise/run=x

Then ask the calculator for the inverse tangent (inv tan)—-that’s the angle. Here’s an example:

If you’re cutting this on a miter saw or table saw, remember that the angle scale is 90 degrees off. (“0” on the scale is a 90 degree angle) So if, as in the example, you want to cut a 53 degree angle, you set the scale to 37. Don’t blame me—-blame the guy that developed the scale.

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MT_Stringer

2850 posts in 2691 days


#5 posted 06-26-2015 03:49 AM

Does this help?

The angles add up to 90 deg…or 180…or 360.

My example uses 30/60 deg angles.

-- Handcrafted by Mike Henderson - Channelview, Texas

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JK0702

131 posts in 1591 days


#6 posted 06-26-2015 04:52 AM

Jerry,
Thanks for the diagram and information. It helps a lot, and make sense. I understand everything except how to find the inverse tangent. How did you get 53.13 degrees from 1.333?
Thanks,
John

-- John - Huntington Beach, CA --- Growth occurs when we get out of our comfort zone.

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JK0702

131 posts in 1591 days


#7 posted 06-26-2015 04:56 AM

pjones46,
Jerryminer’s diagram shows the support piece I am referring to.
John

-- John - Huntington Beach, CA --- Growth occurs when we get out of our comfort zone.

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JK0702

131 posts in 1591 days


#8 posted 06-26-2015 05:01 AM

MT_Stringer,

Your diagram shows what I’m trying to do, but do you have a simple way of figuring what angle to cut the diagonal piece in your example? Jerry Miner’s rise and run formula makes sense, do you have a simpler method?

Thanks,
John

-- John - Huntington Beach, CA --- Growth occurs when we get out of our comfort zone.

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jerryminer

528 posts in 901 days


#9 posted 06-26-2015 05:44 AM



Jerry,
Thanks for the diagram and information. It helps a lot, and make sense. I understand everything except how to find the inverse tangent. How did you get 53.13 degrees from 1.333?
Thanks,
John

- JK0702

after dividing, and getting the result (1.33) I hit the inv tan key on my scientific calculator and 53.13 shows up.

If you use SketchUp, you can draw the rise and run and measure the angle with the protractor tool

View pjones46's profile

pjones46

986 posts in 2102 days


#10 posted 06-26-2015 06:00 AM

John.
As above it is based on trig. That being said, the angle changes every time you change one of the distances and unless you make those distance fixed you will have to make the angle cuts different. That is not practical unless every table or bench you make is exactly the same size and design as the angles change.

-- Respectfully, Paul

View runswithscissors's profile

runswithscissors

2176 posts in 1485 days


#11 posted 06-26-2015 07:33 AM

You can use spring clamps to fix a square of poster board at each end of a stick that’s about the right length. Hold that in place between your horizontal surfaces, and rotate the poster board pieces until they are snug against your surfaces.

No math involved—sorry about that.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View weldoman's profile

weldoman

114 posts in 1517 days


#12 posted 06-26-2015 10:11 AM

Draw it out on a piece of cardboard, transfer the angle with a bevel square , done deal.

-- missouri, dave

View rwe2156's profile

rwe2156

2187 posts in 940 days


#13 posted 06-26-2015 11:21 AM

Scrap wood/get it close/dial it in/use as a pattern?

-- Everything is a prototype thats why its one of a kind!!

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weldoman

114 posts in 1517 days


#14 posted 06-26-2015 12:42 PM

Instead of a bevel square you can use a speed square to find the angle. There is also a triangle calculator app for your smartphone.

-- missouri, dave

View daddywoofdawg's profile

daddywoofdawg

1010 posts in 1035 days


#15 posted 06-26-2015 03:05 PM

If you know the longest side,cut a scrap piece that size,place it next to the board at the point you want,i.e the corner of the board you cut,do that on both ends,draw a pencil line at the intersections on both e
nds,cut one end on the line,test fit,all good,cut the other end test, all good,use the board as a template,no math!

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