Comments on: Octagons Made Easy

By: geppetto425

geppetto425 — Wed, 12 Sep 2012 07:07:43 +0000

Woodsmith magazine had plans a number of years ago for a pencil post bed. They devised a fairly simple jig that slides along your table saw fence to cut the octoganal bed posts, worked great. Still sleeping on that bed.

By: aschaffter

aschaffter — Wed, 12 Sep 2012 03:28:13 +0000

Here is a link to the method I described. It omits the diagonals and goes right to drawing the circle and tangents.

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

By: swirt

swirt — Wed, 12 Sep 2012 03:05:47 +0000

If the taper is not needed, using a marking gauge instead of the compass works pretty cleanly. This method, along with the spar gauge and ruler methods are covered here http://www.timberframe-tools.com/techniques/making-square-stock-octagonal/

By: PhilS

PhilS — Wed, 12 Sep 2012 01:02:19 +0000

I understand completely.

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.

By: Ed Burns

Ed Burns — Tue, 11 Sep 2012 21:59:44 +0000

End result appears complex, yet done so simply. Great tip ! Thanks Chris.

By: aschaffter

aschaffter — Tue, 11 Sep 2012 20:49:05 +0000

As much as I respect Chris, there is a major flaw in his method- it can be difficult to place the point of the compass at the corners- just watch him draw the second arc- it doesn’t meet at the center.

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.

By: William Duffield

William Duffield — Tue, 11 Sep 2012 14:41:07 +0000

If you twist the gauge to keep the dowels rubbing against the sides of the stock, and if the stock is tapered, then the pencils move progressively inwards, or outwards, depending on which direction you move the gauge.

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.

By: Megan Fitzpatrick

Megan Fitzpatrick — Mon, 10 Sep 2012 14:34:55 +0000

fixed. We’ll see if it stays fixed!

By: Megan Fitzpatrick

Megan Fitzpatrick — Mon, 10 Sep 2012 14:27:52 +0000

This is weird. I’m looking into it.

By: JEBreen

JEBreen — Mon, 10 Sep 2012 03:35:29 +0000

Another way to lay this out uses a framing square and the “7-17″ rule. Lay the 24″ leg (or any 24″ rule) on a face with one end on one side, the other end flush with the other side. Simply mark the 7″ and 17″ locations and extend your lines parallel to the edges. Of course, this works well for framing or large masts. For small furniture parts, scale down. Use a 12″ rule and mark at 3 1/2″ and 8 1/2″. Or half of that. Knowing the 7:17:24 ratio will get you there.

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