http://bobhamswwing.com/Articles/Cutting%20an%20Octagon/Cutting%20out%20an%20Octagon.htm

]]>Using a spar gauge, I will taper the already fair piece to accommodate the offset of the gauge, I will use the gauge, and then I will taper again working down to the lines just drawn by the spar gauge.

Using a compass and a straight edge, I need two adjacent fair sides to align the rectangle at top and bottom, a compass, and a straight edge to align the sides scribed with the compass.

I draw the two rectangles at top and bottom using the two adjacent fair sides (maybe an off-cut?) and then scribe the shape as the video shows. I then mark the lines using a straight edge. I cut to the lines marked form the rectangle and plane the edges to produce the octagon.

So, I do more marking with the compass and straight edge but less pre-work getting the piece ready. I can also cut to the ratio of my choosing instead of the one specified by the spar gauge.

So while it is true that one cannot make a silk purse from a sow’s ear, one can make a silk purse from silk woven by silk worms if one knows the steps to follow.

Anyway, enough of this. Thank you for your time and explanation and good luck with your woodworking.

]]>Easiest, most accurate method:

1. Draw diagonals

2. Draw inside circle, tangent to sides

3. Using a combination square or 45, draw tangents to the circle where it crosses each diagonal.

Result: perfect octagon; no measuring.

]]>The only thing that is important is to start with a blank with two pairs of mutually perpendicular faces. Whether it is straight, or tapered, or even curved (like a cabriolet leg), you end up with a pair of lines on each face. If you then remove the corners up to the lines, the four new facets formed end up the same width as what is left of the facets you started with.

You can’t make a silk purse out of a sow’s ear. So, no matter how you try to lay it out, it is imperative that you start with four fair faces.

If you are really interested, and don’t understand it from our explanations and the diagrams in the link that Pete provided, just build one and try it out.

]]>I built a small spar gauge using this ratio. Works great. Once its built, you can just grab it and layout your lines, tapered, curves, or straight.

Jason

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