What's the formula for determining the exact distance across the flats of an octagon inside a circle of a given diameter, in this case it is an odd size of 1.033.
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From google W=.9239D, where W = width of the octagon and D = the circle diameter. If I understand what you are looking for correctly,
1.033 * 0.9239 = .9543887.
Edit  this is for an octagon with the points (vertices) touching the inside of the circle.Last edited by Ridgerunner; 06122011, 05:21 PM.
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Originally posted by radkinsWhat's the formula for determining the exact distance across the flats of an octagon inside a circle of a given diameter, in this case it is an odd size of 1.033.
EDIT: Which I see does not agree with the book. Hmmm..
"People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill
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Isn't it sin(22.5).
Phil
Originally posted by TGToolYou know that the base angle of each section facing the flats is 360 divided by 8 or 45 degrees. Dividing that to get a right triangle for trig gives 22.50 degrees. Then you know the length of the hypotenuse is 1/2 the circle diameter so half the distance across the flats is (1.033/2) * cos 22.5, and the across flats distance is twice that or .95436.
EDIT: Which I see does not agree with the book. Hmmm.
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Originally posted by philburIsn't it sin(22.5).
Phil
sine = p/h
cosine = b/h
tangent = p/b
One thing I was missing was not multiplying the book constant by 1.033 so I think I'm out of the woods now..
"People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill
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The distance across the flats is just diameter x cos 22.5 which is .92387. The book said .9239.
I don't understand what your 1.033 is Tgtool.
Philbur, I always work everything out from cos. In this case, sin will give you the length of the flats.Richard  SW London, UK, EU.
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Originally posted by TGToolSome People Have, Curly Black Hair, Through Persistent Brushing
sine = p/h
cosine = b/h
tangent = p/b.
don't look/sound like any parts of a triangle I've ever seen .
I guess h may be hypotenues, but p and b for adjacent and opposite?????????
...lew...
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Originally posted by Lew Hartswick?????? p h b ??????
don't look/sound like any parts of a triangle I've ever seen .
I guess h may be hypotenues, but p and b for adjacent and opposite?????????
...lew...
Originally posted by rohartI don't understand what your 1.033 is Tgtool..
"People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill
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Originally posted by radkinsWhat's the formula for determining the exact distance across the flats of an octagon inside a circle of a given diameter, in this case it is an odd size of 1.033.
You could download a free copy of Draftsight 2D CAD. Very handy for these and other type problems of this sort.
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