Help in Making an Octagon

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I have a 4" square piece of wood that is 15" long. I need to make it into an octagon. A table saw with blade tilted at 45 degrees won't do it. How do I cut the corners off?
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Why?
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CW wrote:

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Cause it is eight sided, divide 360 buy 8 then by 2 and your answer lies there. (Hint there are 16 ends to eight sticks)
Mark (sixoneeight) = 618
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And what does this have to do with making an octagon on a table saw, and why can't you put the blade to 45 degrees and run all four sides through? Seems pretty simple to me.

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On Sun, 15 Apr 2007 01:13:41 GMT, "Scott"

Well let see an octagon has eight sides not four. Perhaps the angle is 22.5? Or is your mind totally stuck in the box.
(Hint 45 + 45= ?) and #2 (22.5 + 22.5 = ?)
Mark (sixoneeight) = 618
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<<Well let see an octagon has eight sides not four. Perhaps the angle is 22.5? Or is your mind totally stuck in the box.>>
Yes, an octagon has 8 sides and it has 8 equal angles. The angles in a polygon have to add up to 360 degrees. Divide 360 by 8 and you get -- wait for it -- 45 degrees.
If the O.P. wants to turn a length of 4" x 4" (true dimension) stock into an octagon, he needs to measure one inch from the edge, tilt his table saw blade to 45 degrees and set the fence so the blade hits that one-inch mark, run the piece, then repeat the cut three more times, rotating the piece 90 degrees each time. If he's using a 4x4 (IOW, a piece that's actually 3.5" x 3.5") he needs to make his mark at 7/8" instead of 1".
Lee
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Actually you want the 45 degree bevel to begin at 1-11/64" from each corner, leaving 1-21/32" in the center for actual 4x4.
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I probably didn't really make myself clear on my setup. My table saw blade tilts to the right and my fence is on the right.
Perhaps I'm missing something, but if I try to run the stock through the table saw and cut off the lower right corner of the cross section, that seems like an extremely dangerous cut to make. The cutoff piece would be against the fence.
If I can move the fence to the left side of the blade, it would be a much safer cut. But, I don't think I can do that. :(
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OK, that makes much more sense. Most right tilt saws will let you move the fence to the left side of the fence 8-12" and that would be the way to do it.
Or use a 45 degree chamfer bit on a router.
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Personally, I wouldn't sue the fence in that situation, at least not having the work piece running continually along the fence. I would use either a miter gauge with an extension fence and a stop block to get the length, or a cutoff sled. If you want to use the fence for position, I would add a temporary fence piece that is entirely in front of the blade. Hold the work against the miter gauge with the end touching the temporary fence and then move through the cut. As you bring the work to the blade, the cutoff would no longer be against the fence and there would be less chance of it binding up.
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<<If I can move the fence to the left side of the blade, it would be a much safer cut. But, I don't think I can do that. :( >>
I've never seen a table saw that didn't allow for the fence to be moved to either side of the blade. You are correct that making the cut you described on a right-tilt saw with the fence to the right of the blade is an invitation to a kickback. But you ought to be able to completely lower the blade, slide the fence to the left, raise the blade back up, tilt it to 45 degrees, and proceed with the operation. You'll just be doing it "backwards" from the way those of us with left-tilt saw would do it.
Do you have a jointer? You could try tilting it's fence to 45 degrees and nibbling the stock away 1/16" at a time. Of course, that would take practically forever. <g>
Lee
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I tried that, but my fence has a big old piece (the clamping mechanism) on the right side of the fence. That leaves no infeed area.
The jointer approach is probably the safest way to do this job even though it'd just be nibbling away. There's only 4 cuts that need to be made.
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<<Actually you want the 45 degree bevel to begin at 1-11/64" from each corner, leaving 1-21/32" in the center for actual 4x4. >>
You're right. I flip-flopped the two equal sides with the hypotenuse. (Would have made measuring easier, though. <g>)
Lee
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I cheated and used a CAD program.
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If you have eight sides, you have *sixteen* cuts (two on each board - one at each end). Divide 360 by 16 and you get 22.5.
Plus, the angles of a polygon do not add up to 360. They add up to 180(n-2) where n is the number of vertexes. The *bevels* add up to 360, with '0' meaning unbeveled (square cut end).
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Sun, Apr 15, 2007, 11:10am snipped-for-privacy@delorie.com (DJDelorie) doth proclaimeth: If you have eight sides, you have *sixteen* cuts (two on each board - one at each end). Divide 360 by 16 and you get 22.5. <snip>
Wow, impressive, that must be some of that new college math - calcluclueless, eh? I learned the old fashioned math, where if you had a square (four equal sides), and knocked off the four corners (which would be four cuts), you'd get an octagon (eight sides). I'm always ready to learn somthing new - so how about learning me where you came up with the extra cuts?
JOAT I have anal glaucoma. I can't see my ass going to work today.
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<<If you have eight sides, you have *sixteen* cuts (two on each board - one at each end). Divide 360 by 16 and you get 22.5.>>
That's true if you are constructing a hollow octagon out of eight individual pieces. The ends of each of those pieces are cut at 22.5 degrees because it takes two of them to form the necessary 45 degree angle. But the O.P. isn't trying to assemble an octagonal-shaped "ring." He is looking to cut a solid octagon out of a solid square by clipping each of the four corners off the square. To do that, he needs to set his blade to 45 degrees.
Lee
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To e-mail, replace "bucketofspam" with "dleegordon"

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45 it is.
wrote:

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wrote:

Have you ever cut a bevel on a TS??? I am not sure what your formula represents but it has nothing to do with cutting an octagon out of a square.
8*4560. Since cutting 1/3 width off at the corners creates 2, 45 degree angles, you need only rotate the piece 90 degrees 3 times and cut after the first 45 degree cut.
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