Roubo Curves are metal french curves made by Sterling Tool Works. These are precision cut, thick gauge curves that will let you draw curves on full scale drawings. The Roubo curves will last a lifetime!


The largest curve in the 3 piece set is 18 inches long. The set is made from 304 Stainless Steel cut with a laser and has a matte finish that is easy on the eyes for layout work. The smaller curves are 8 – 9 inches long. The metal curves are thick enough so that they will not bend and they provide a nice bearing surface for your pencil to track around. You could even track a knife edge around the metal surface but I would recommend you stick with a pencil and not nick the edges with a knife blade.

You may have heard the term "French Curves" but what exactly is it? A french curve is a template usually made from plastic, metal or wood and is composed of many different curves along its surface...both interior and exterior. They are used in manual drafting to draw smooth curves of varying radii. Technically, the shapes are segments of the 'Euler Spiral'.

A what? What is a Euler spiral? Well, this is what it looks like:


The Euler spiral is a curve whose curvature changes linearly with its curve length. So, all this means is that these various curve segments are used as transition curves in engineering drafting for connecting and transitioning the geometry between a tangent and a circular curve. Clear?!

Now that we have cleared up what a french curve is, how does it work? If you have a sequence of points that you want to draw a smooth line through, you can use a french curve to draw a series of line segments that will flow through all of the points. As shown in the diagram below, you can select a section of the french curve that best fits the first three points and another segment that fits the next part of the curve. You walk your way along the curve in this manner. You are connecting the curve of one segment into the tangent of the next segment to provide a continuous smooth curve among all the points.


The large size of Sterling's Roubo Curves lets you draw these smooth curves on full size drawings as well as directly onto your wood pieces. For example, if you were drawing the curves along the lower rail of a low boy, you could draw them in full size with these templates. The following picture shows an example of using Sterling's Roubo Curves to transfer the shapes from this low boy to a board. You can mark the transition points and then use the various segments of the curves to draw a smooth curve as described earlier.


The exceptional quality of Sterling Tool Works products is once again on display with these Roubo Curves. The unique sizes of the set of curves make them very practical for woodworkers to use. I recommend you pick up a set to improve your hand drawn layouts.

Jeffrey Fleisher has been a woodworker for approximately 20 years and a professional woodworker for the past 6 years. He is the president of his local woodturning club, the Woodturners of the Virginias and past president of the Northern Virginia Carvers. You can see some of the furniture he has made at www.jeffswooddesigns.com . He can be reached by email at furnmkr@gmail.com .