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Layout and Measuring Tool and their Makers

  8-Siding or Octagon Marking Gage by Bob Smalser 1 of 2  

All the descriptions I’ve ever read on these needed a good picture, so I thought since I made another one recently, I’d take a pic.

These mark square or rectangular stock into 8 sides, dividing each face of the stock into three equal sections… the first step in planing a cylinder from a square.

The nice feature of this design is that it accommodates tapered stock, so is perfect for spars and the oars I am making here.

Cut a block the diameter of the largest cross section of your finished spar or loom…draw a circle in it so the circle intersects the edges. Then use a 45 degree square to make an octagon of it…keeping outside of your pencil lines.

Another block an inch wide and a couple inches longer than the first block is laid atop…both the edges of the circle and the corners of the octagon are transferred to the second block, holes drilled for nails and pencil… and you have your gage. Offset the holes for the guide nails to insure they are outboard of the circle.

Then merely keep the guide nails in contact with the edges of your stock, and you can mark any tapered piece into an octagon for planing. In traditional construction, spars and looms are thought to look best if the faces of the octagon have a ratio of 5-7-5 instead of 1-1-1, and many go to a lot of trouble making gages that mark those offset lines. My approach is simpler…I mark a perfect octagon and then plane either outside or inside of my marked lines to get the look I want:


Woodworker's Guide to Wood Collection only $79.99 at Shop Woodworking
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Marking Gauge



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