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Spar Gauge (8-sided)

Designed by  2

  • Tool to create round masts from square stock
  • Marks where to plane to create an 8-sided beam
  • Made in the Netherlands 🇳🇱
  • 3D printed with highly accurate dimensions 📏
  • Can also be used to mark center lines
Spar Gauge 8 Sided

Trying to make a perfectly round mast? With this spar gauge you can turn any square stock into an 8-sided beam. 

Because it is 3D printed, the dimensions are much more accurate than DIY spar gauges. This helps you plane more accurately, which helps you achieve a cleaner and more accurate end product.

Spar Gauge 8 sided
Scroll down for more images

It can also be used as a center finder, thanks to the middle hole. The holes fit regular pencils and the pencils are secured with small knobs on the side.

  • Max width of stock: 144 mm 📏
  • Hand Made in the Netherlands 🇳🇱
  • Precise 7 : 10 : 7 ratio

In the short video below you can see how the spar gauge is used.

Spar Gauge Design

I designed this spar gauge for a friend who builds small sailing boats. Spar gauges can also made from a piece of wood, but without an accurate drill press and a perfectly square piece of wood it is quite tricky to make them accurate.

  • By using a 3D printer you are guaranteed to have everything in the right proportions and dimensions.
  • This spar gauge uses an 8-sided proportion of 7 : 10 : 7. The distance is measured from the side of the guides to the tip of both of the pencils.
  • It can be used on stock up to 144 mm wide. There is no minimum width.
  • The pencil holes are 7.5 mm in diameter and fit standard European sized pencils.
  • The small curves help get a good and comfortable grip of the gauge in use.
  • Brass threaded inserts ensure smooth operation of the knobs.

Detailed Images

Spar Gauge Detailed Knobs
Spar Gauge Overview
Spar Gauge without Pencils
Spar Gauge Detailed View

Customization & Contact

If you’re looking for a large spar gauge (for stock wider than 144 mm), or have other ideas for customization, please contact me via I’d be happy to design a gauge for your specific requirements.

Have a 3D printer yourself? You can also download the 3D model of this spar gauge and print it yourself!


  1. Hi
    Im in Australia and would like to buy a Spar Gauge (144mm) On line purchase form does not have option for Australia. Is this possible

    Steve Marks
    • Hi Steve, unfortunately shipping to Australia is very expensive. But if you download the free 3D model, you can send it to a local 3D printing company near you and they should be able to print it for a reasonable price as well.

      Hope that helps, Rob


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