?on miter cut.

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Chris,
Have you family ties with B.A.D.? Or just blood brothers?
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Think thrice, measure twice and cut once.

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You are correct.

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I've never seen so much bickering and misinformation in my life as there is in this thread.
Even Doug who is usually right on target is off a bit on this one. Doug's formula is for the sum of the INTERIOR angles.
The sum of the EXTERIOR angles = 360 for any regular polygon of ANY number of sides. Including triangles and squares. The EXTERIOR angle of said polygon is 360 / n The INTERIOR angle is = 180 - (360 / n)
Art
"Doug Miller" wrote in message...

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Right you are. 'Scuse me while I hunt around for a shop rag to wipe some of that egg offa my face. :-)

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)
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<...snipped...>
Aww, come on. There have been much worse threads than this one.
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Larry Wasserman Baltimore, Maryland
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On Sun, 18 Apr 2004 23:15:17 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

That is also false.
I'm tired of this, so here's the proof:
For any closed polygon, pick any point in the interior. Draw lines from there to all vertices of the polygon. If you have n sides, you now have n triangles. Add all angles, and you have n*180, the sum in all of the triangles (**). However, that includes all of the angles at the interior point. They add to 360, so subtract that [360 2*180] So you sind up with the angles at the vertices, the "interior" angles, adding to (n-2)*180.
Draw lines to continue each side in the same direction each time to look like one of those wheeled firecrackers. The small angles so obtained are what are referred to as the "exterior" angles of a polygon. Now, all of the outside anlges add to each inside angle to produce n lines, or n*180.
So, the exterior angle sum is found by subtracting: (n-2)*180 - n*180 = 2* 180 = 360.
If the polygon is "regular', all sides are the same length and all interior angles are the same measure. So divide by the number of sides = number of angles to get the size of each one.
(**) Proof for the triangle, the basis for all of this, depends on the fact that angles on paralallel lines crossed by a line are the same. It is the start, not the end. The others are built from triangles.
Period.
Dan.
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OOps! Too much of a hurry. The other away around: n*180 - (n-2)*180 = 2*180 = 360.
Dan.
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"Chris Melanson" wrote in message

Yes, but you obviously didn't.

I don't have to ... the angle you are actually cutting when you set your saw to cut 36 is the complementary angle, 54 degrees.
Go out to the shop, cut a 36 degree angle on your saw, then measure the angle you just cut.
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PLEASE read the OP

Bob's not asking for the angle in the piece of wood he's just cut
Bob's asking what degree would he need to cut the 2 x 4's. He needs an angle of 36.
Graham

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"Chris Melanson" wrote in message

Yes, but only part of the story. Exterior angles equal 72, interior angles equal 108.

The right answer, but you appeared to be going about it for the wrong reason:

As stated, it doesn't have to. What you are leaving out, or failing to mention, is the concept of complementary angles.
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What am I leaving out ? The concept of complementary angles is that mating MITERS of 36 degrees result in a angle of 72 degrees and in order to obtain a pentagon you have 5 sides and 5 * 72 is 360. But a MITER of 54 degrees would result in an angle of 108 and 5 * 104 = 540 not 360 which is what a circle consist of in degrees.So how would you obtain a closed polygon consisting of 540 degrees? Can you not see that? The "OP" asked "My wife would like a 5 sided planter. Just thinks it would look cute?? I am not a wood worker but, have access to a compound miter saw. What degree would I need to cut the 2x4's to achieve this? They will each be 27" long.
CHRIS

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wrote:

No it doesn't. It consists of five 108-degree angles.

No, it's an absolute falsehood. The sum of the exterior angles of any closed polygon of n sides is (n - 2) * 180 degrees. It's 360 *only* for four-sided figures, where (4 - 2) * 180 = 2 * 180 = 360.

Which means a 54-degree angle on each piece. Combined, those make a 108-degree angle.
Get a pencil, paper, and protractor, and draw it out yourself.
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On Sun, 18 Apr 2004 23:17:38 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

You mean the sum of the "interior" angles is (n-2)*180. Otherwise OK. The exterior always all add to 360.
Dan.
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The funny thing about this is that you set the saw to 36 degrees. 54 degrees is the measured result. 90 degrees -36 degrees = 54 degrees. You always count the number of cuts you need and divide that number into 360.
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Why do we have to insult each other?
What happened to an exchange of ideas and constructive criticism?
Rob

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"Rob" wrote in message

Microsoft.
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In rec.woodworking

The one lacking common sense is you Chris. You use 45 to get 90 degree corners in a square. A pentagon has obtuse angles bonehead. Let's bet before you go look at a.b.p.w to see the AutoCAD drawing I posted.
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Bruce I looked at your drawing Do you not see your mistake ??????? Even your drawing shows 54 Degrees. Seeing that you cut your MITER off a fence or table saw that is set to 90 degrees from your blade being set at 0 Degrees. DO YOU NOT GET 36 FROM SUBTRACTING 54 FROM 90 ?????????? Is that not what you would have to set your saw to ????? 36 degrees is your miter try actually building something for once. You are why CAD programs get such a bad name. CAD programs do give the right information it is how one is able to interpret the information give to be able to put it into practice.
CHRIS
to quote you "lets make a bet" then lets go and build one to prove it I will wager $ 100.00 Canadian to prove my point that you have to set your miter to 36 Degrees will you?
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In rec.woodworking

There is no mistake in the drawing Chris.

Yes, if that is the question, then you have to set your saw at 36 degrees to achieve the required 54 degree angle.

I didn't know CAD programs had a bad name? If someone interprets that drawing WRONG and sets the saw to 54, that isn't my fault.
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You are the one who has interpreted the information wrong by reading it as 54 when in order to make that cut it is in reality 36 what you would have to set your saw to. And yes CAD programs do have a bad name in the millwork industry and are generally pretty pictures with overall sizes on them . Unless you have somebody with experience in joinery as a draftsperson. You cannot trust CAD drawings in the real world. That is why cabinetmakers do full size layouts most of the time.
CHRIS
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