TIP: Homemade angle finder inspired by Doug's Dec. 8th math question

Guys and gals, I have found myself many times without some way to measure or find an angle. I had this happen while bending the HS spars, setting hand plane blades in a honing guide, etc. There is a relative easy way to find an angle using a little math and a piece of cardboard. The process might look complicated but I assure you if you do it a couple of times it gets fast. I can do this in less than 2 minutes. This also works for an outside angle, just make your "flat area" up a bit from the bottom and draw your right triangle downward instead of up.

Perhaps there is an easier way to do this but this method has always served me well and is surprisingly accurate. Would be even better if you used metal!

Step 1 get some flat area (about 4-5 inches) and mark a 4-6" line next to it.

20171210_095448 by Jereme Carne, on Flickr

Step 2 decide on the angle you are interseted in and do some simple math.

20171210_095804 by Jereme Carne, on Flickr

Step 3 take the results from step 2 and mark it on the vertical line depicted on the right of the above picture. The results from step 2 represent the side of the triangle opposite the angle.

20171210_095743 by Jereme Carne, on Flickr

Step 4 draw a line (aka the hypotenuse of the triangle)

20171210_095907 by Jereme Carne, on Flickr

Step 5 cut out what is needed and enjoy your new tool.

angle finder by Jereme Carne, on Flickr

Wouldn't a protractor be a bit simpler?

Mike S said:

Wouldn't a protractor be a bit simpler?

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Mike you are correct but I don't always have one.

Neither do I, but your math makes my head hurt.....

Mike S said:

Neither do I, but your math makes my head hurt.....

Click to expand...

Haha fair enough, just slam line 3 into a calculator (with whatever angle you want) and hope I didn't make a mistake.

No head hurting involved

Mike S said:

Neither do I, but your math makes my head hurt.....

Click to expand...

No need for hurting heads if you have a PC at hand....

Tan of X degrees here -

https://www.rapidtables.com/calc/math/Tan_Calculator.html

= 0.10510424 for the 6 degrees quoted

Multiply by the baseline you want to get the size of the angle template you want, 4 inches in the case above.

0.10510424 x 4 = 0.42041696

Measure on the cardboard template to whatever accuracy you want.

No mathematical headaches involved. Simply quick and easy.

az_gila said:

No need for hurting heads if you have a PC at hand....

Tan of X degrees here -

https://www.rapidtables.com/calc/math/Tan_Calculator.html

= 0.10510424 for the 6 degrees quoted

Multiply by the baseline you want to get the size of the angle template you want, 4 inches in the case above.

0.10510424 x 4 = 0.42041696

Measure on the cardboard template to whatever accuracy you want.

No mathematical headaches involved. Simply quick and easy.

Click to expand...

Thanks for the added reference to the calculator Gil!

Jereme, thanks for the refresher although I haven't needed to use it in a long time, I had nearly forgotten about SOH CAH TOA from Trigonometry.

ryschneider said:

Jereme, thanks for the refresher although I haven't needed to use it in a long time, I had nearly forgotten about SOH CAH TOA from Trigonometry.

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No problem Ryan, anytime I can teach a bit of math (especially when it applies to something) is a good day.

Mike S said:

Wouldn't a protractor be a bit simpler?

Click to expand...

Not neessarily. With a protractor, your accuracy is limited by the size of the protractor, and your ability to set the corner point on the reference line of the protractor accurately, which is not always as clear as it should be.

With this technique, you can scale up the whole geometry so that measurement error has a smaller effect on the angle. If you need a durable angle, use some masonite or thin aluminum sheet.

Fastest way to find the tangent of an angle

I just use the ?compass? app on my phone. It has a second screen that acts as a digital bubble level. You can even ?zero? it to any arbitrary starting point.

Very cool Dave! I'm only 30 so needless to say I never got to use one of those in school.

Glen, I wonder how accurate that would be? I have however used the phone angle finder when I needed to find the pitch of my roof.

Apple app

The trouble I have with the apple app is that it is not very accurate. Only within 1 degree wont cut it fo me.
But if I use it for comparison angles by double tapping it seems much more accurate.