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How do i cut this angle, with the boards being angled as well?

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Forum topic by FancyShoes posted 04-19-2015 06:02 PM 1443 views 3 times favorited 27 replies Add to Favorites Watch
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FancyShoes

509 posts in 830 days


04-19-2015 06:02 PM

Its a trianlge shape, i used to know trig, but it has been a few years.


27 replies so far

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Dallas

3599 posts in 1953 days


#1 posted 04-19-2015 06:04 PM

Tilt your blade, angle the miter gauge.

-- Improvise.... Adapt...... Overcome!

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FancyShoes

509 posts in 830 days


#2 posted 04-19-2015 06:08 PM

Is it a 45 degree?

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FancyShoes

509 posts in 830 days


#3 posted 04-19-2015 06:11 PM

Ok never mind, it is 60 degrees makes all side equal. So what degree do i tilt the blade to angle the wood as well?

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altendky

169 posts in 1676 days


#4 posted 04-19-2015 06:36 PM

It depends on the angle you want. :] If your boards are vertical then it’s a simple 60degree angle to the face. If you boards are flat then it’s 90 to the face but 60 degrees to the edge. In between? It’s somewhere in between. I haven’t used it but I think this site will calculate what you need.

http://jansson.us/jcompound.html

I have a set of birds beak joint router bits that say you can do stuff like this but it’s never made sense to me since they can’t change their angle…

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Dallas

3599 posts in 1953 days


#5 posted 04-19-2015 06:39 PM

YOu always want everything to add up to 90or 180. In that case, 2- 45° = 90°, 4- 22.5° = 90°, 3- 60° =180°.
Since the conjunction of two line segemnets is 60°, each angle of the conjunction would be 30°, meaning that it would take 3- 30° to equal 90°.

Clear as mud?

-- Improvise.... Adapt...... Overcome!

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WoodNSawdust

1417 posts in 643 days


#6 posted 04-19-2015 06:41 PM

I agree with Dallas. My understanding that each board receives half of the angle so 60/2 = 30 degrees.

-- "I love it when a plan comes together" John "Hannibal" Smith

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NoThanks

798 posts in 995 days


#7 posted 04-19-2015 06:54 PM

It’s NOT going to be a 30 degree angle!

-- Because I'm gone, that's why!

View BobAnderton's profile

BobAnderton

219 posts in 2256 days


#8 posted 04-19-2015 07:02 PM

altendky gave you a good link, but this one is good too. It’s a non-trivial thing to figure out and this site provides a splayed miter angle table.
http://woodgears.ca/miter/

Either a compound miter saw or the tablesaw will cut in two planes at once, and the site above goes into quite a bit of detail on how to make the cuts with the tablesaw.

-- Bob Anderton - Austin, TX - Nova 3000 lathe, Alaskan Mark III mill, Husqavarna Saw

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BurlyBob

3695 posts in 1732 days


#9 posted 04-19-2015 07:09 PM

get yourself a digital bevel gauge and a digital protractor if you don’t have them already. I’ve found them indispensable when dealing with angles on a compound miter saw or table saw.

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TheFridge

5765 posts in 952 days


#10 posted 04-19-2015 07:23 PM

looks like a 60 degree miter and bevel. Bevel has to be 60 for each end. 6×60 deg=360 deg

Just like 8×45s = 360 for a box.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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NoThanks

798 posts in 995 days


#11 posted 04-19-2015 07:44 PM


looks like a 60 degree miter and bevel. Bevel has to be 60 for each end. 6×60 deg=360 deg

Just like 8×45s = 360 for a box.

- TheFridge

”Just like 8×45s = 360 for a box.” wrong!

When you add spring angle it changes the miter/bevel!

-- Because I'm gone, that's why!

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altendky

169 posts in 1676 days


#12 posted 04-19-2015 08:25 PM


looks like a 60 degree miter and bevel. Bevel has to be 60 for each end. 6×60 deg=360 deg

Just like 8×45s = 360 for a box.

- TheFridge

”Just like 8×45s = 360 for a box.” wrong!

When you add spring angle it changes the miter/bevel!

- NoThanks

Yep. Just think about cutting for a picture frame vs. cutting for the sides of a box. 45deg in both cases but the frame is 45 to the edge while the box is 45 to the face. In the middle you end up with a compound miter and the angle to both the edge and the face vary depending on the ‘spring’ angle (as NoThanks referred to it, I don’t know what the ‘correct’ term is).

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TheFridge

5765 posts in 952 days


#13 posted 04-19-2015 09:08 PM

Gotcha

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View Dallas's profile

Dallas

3599 posts in 1953 days


#14 posted 04-19-2015 09:28 PM


looks like a 60 degree miter and bevel. Bevel has to be 60 for each end. 6×60 deg=360 deg

Just like 8×45s = 360 for a box.

- TheFridge

”Just like 8×45s = 360 for a box.” wrong!

When you add spring angle it changes the miter/bevel!

- NoThanks

Just for fun, show me a stationary tablesaw of standard make that will cut 360°.

The table saws I work with cut somewhere less than 90°. In order to get to 360°, the angles need to be added together to get your 360°.
In the mean time the blade only tilts to the right or the left. There is only a maximum of 45° to work with because that is all the blade can move.
The miter gauge can move both ways, but to get an accurate cut, it is better to set it once and turn the piece being worked on.

-- Improvise.... Adapt...... Overcome!

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Combo Prof

2385 posts in 744 days


#15 posted 04-19-2015 10:00 PM

If what you are making is a truncated tetrahedron you want to sent the saw baled angle to 1/2 the dihedral angle of the tetrahedron. The dihedral angle of the tetrahedron is arccosine(1/3)=70.528779° not 60°. If the boards are to be vertical then yes it is 1/2 of 60°, but the picture shown looks to me to be a truncated tetrahedron. The miter gauge would however be set to 60°. To believe this here is what I suggest you do. Build a tetrahedron by taping together 4 equal sized equilateral triangles. Use your your bevel square to get the angle. (I.e. check that it is indeed 70.528779°). When you do make the cut. I suggest undercutting the dihedral angle by half a degree. You’ll get a better fit particularly if you use glue.

A dihedral angle (also called the face angle) is the internal angle at which two adjacent faces meet.

-- Don K, (Houghton, Michigan)

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