I need help with angles....

[Bill Huber]

I am wanting to make a top to a box that is shaped like the picture. (only with all 4 pieces in it)

It will be 4 inches on a side and 1 3/8 high. I will be using 3/8 in stock.

I can not get my angles right, I know I have to make a compound angle.

With the blade on the table saw set and angle X degrees and the miter gauge set at Y degrees I should be able to cut it.

The problem is I can not find the angel X or Y.



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[Rusty Eads]

Not having my morning breath of sawdust to wake me up i googled your problem and found this website that gives a calculator to figure your angles. All you need to input is the length of your sides, the number of sides, and the angle of the top tip of one side (if you can understand what i'm trying to say lol). Hope this helps

http://www.slyman.org/m_projects_mathematics_pyramids_polyhedra_intersur face_angle.php

[Jay Allen]

Seems like 39.5* on the miter gauge and 23.6* should get you very close

[David Winer]

I am wanting to make a top to a box that is shaped like the picture. (only with all 4 pieces in it)

It will be 4 inches on a side and 1 3/8 high. I will be using 3/8 in stock.

I can not get my angles right, I know I have to make a compound angle.

With the blade on the table saw set and angle X degrees and the miter gauge set at Y degrees I should be able to cut it.

The problem is I can not find the angel X or Y.
155079 155080
Your question seems to come up here on SMC once in a while. There are a number of "aps" available if you search this forum or the internet, but there is one I prefer: Click here (http://www.sawmillcreek.org/Woodworkers%20Guild%20of%20Georgia,) for an angle calculator with a graphical user interface that is very simple and intuitive. If the link doesn't work, here is the full URL: http://www.woodworkersguildofga.org/ShopHelpers/MiterCalculator.htm

[Myk Rian]

Is that a Sketchup model? If so, it will show you the angles. Look in help.

[Bill Huber]

Is that a Sketchup model? If so, it will show you the angles. Look in help.

Yes it is in SketchUp but I can not get on the correct plain to measure the angle.

I am using the protractor but just can not get it on the correct plain for some reason.

[Bill Huber]

Your question seems to come up here on SMC once in a while. There are a number of "aps" available if you search this forum or the internet, but there is one I prefer: Click here (http://www.sawmillcreek.org/Woodworkers%20Guild%20of%20Georgia,) for an angle calculator with a graphical user interface that is very simple and intuitive. If the link doesn't work, here is the full URL: http://www.woodworkersguildofga.org/ShopHelpers/MiterCalculator.htm


That is getting me closer just have to get the slope angle correct from Sketchup.

[Bill Huber]

Not having my morning breath of sawdust to wake me up i googled your problem and found this website that gives a calculator to figure your angles. All you need to input is the length of your sides, the number of sides, and the angle of the top tip of one side (if you can understand what i'm trying to say lol). Hope this helps

http://www.slyman.org/m_projects_mathematics_pyramids_polyhedra_intersur face_angle.php

Now I just have to figure out how and what data to put in it. I can see now why it is so hard to do.

[Bill Huber]

Seems like 39.5* on the miter gauge and 23.6* should get you very close

I am not even getting close to those numbers with anything.

[Jay Allen]

It comes from the link that Rusty posted. It take some work to get the numbers to line up though. Here is a screen cap of what I came up with..

The chamfer angle shows 66.4 but it needs to be subtracted from 90 to get the saw tilt angle. 23.6*
This is backed-up by the 132.8* (angle between surfaces)
If you subtract that from a flat plain (180*) you get a total angle of 47.2 which must be divided in 2 to get the blade angle 23.6*

The 79* upper point angle must be divided by 2 to get the miter gauge setting because you have to cut the pieces on both sides. 39.5*

The perpendicular height is 1.375 as asked
The width of the outer edges is 4.00 as asked


Test it on some scrap, what can it hurt?

[Phillip Ngan]

Don't bother with calculating angles. They are tricky to calculate, and once you have them, you have to rely on the accuracy of your setup to attain the precise cuts.

Instead, choose the angle of the slope you want. By the looks of your diagram it is around 15 deg. Rip the long edges of your boards at that angle. Then use a mitre saw, prop one of the long edges up against the fence of your saw; cut out a V shape at +45 and -45 deg. Repeat the V cuts three more times, and you are done.

This is how I do my crown mouldings -- makes it easier to deal with walls that aren't perfectly 90 deg too.

[Ray Newman]

Bill H.: don't feel bad about not being able to figure out the angles. Five out of three people have difficulty with math....

[Bob Carreiro]

Hello Bill,
I'm like you - angles confuse me. I looked at your drawing and thought how I would do it.

1) Make a triangle with the hypotenuse equal to the diagonal length of your box (corner to corner) with the opposing angle the height of your cover.
2) Fasten the (hyotenuse) of the pc to a sled, parallel to the TS bade.
3) Cut an over-sized square (1" +/-) of your box material, then cut both diagonals (4 trianglure-shaped pcs).
4) Place two of them up on the legs of the triangled pc of the jig - as if in their glued-up position - and run thru the blade. This will establish the angle.
5) Rotate ea pc on the jig and with the sled on the opposite side of the blade (other miter slot), cut adjoining edges.

This is how I would attempt it. I hope this helps.

Happy WWing,
Bob

[Keith Westfall]

Five out of three people have difficulty with math....


5 out of 3 people don't understand fractions.... :D

[Eiji Fuller]

Don't bother with calculating angles. They are tricky to calculate, and once you have them, you have to rely on the accuracy of your setup to attain the precise cuts.

Instead, choose the angle of the slope you want. By the looks of your diagram it is around 15 deg. Rip the long edges of your boards at that angle. Then use a mitre saw, prop one of the long edges up against the fence of your saw; cut out a V shape at +45 and -45 deg. Repeat the V cuts three more times, and you are done.

This is how I do my crown mouldings -- makes it easier to deal with walls that aren't perfectly 90 deg too.


You can also do this on the TS with a sled. Much easier than trying to fudge with bevel and miter settings.

[Stephen Cherry]

Math?! That's the last thing I would want to do! And I have done a little math.

The problem with all of this, as I see it, is that even if you could calculate a 22.385772 (or whatever) angle, how are you going to measure it.

In my tool kit, I have 90 degrees, 45 degrees (on square and combination square), and I have a scales on my saws, and bevel gauges (many).

The easy way for me to do something like this is to take a piece of solid stock, rip it to the roof angle, lay the flat sides on the compound miter saw, cut 45 degrees one way, 45 degrees the other way, and you have a solid model of the roof with all the angles saved on it. With this, and a bevel gauge. you pick off angles and set whatever tool you would like to make cuts for the real part.

And the little block of wood can be used later to reproduce the same setup.

[Jay Allen]

I tested the angles that were given by the link's method. It was simple enough on the SCMS, the dual bevel helps. Mine is a bit "heavy" looking because I did it out of scrap 3/4 ply, but the point is the same either way...It does work.