Proportion & Design Tool

I’ve used the Golden Ratio as a design guide for years, at the lathe and in the classroom. This tool puts it on screen. Choose a shape, tell it how big you want the finished piece to be, and it works out the rest of the proportions for you. You can then print a full-size template to take to the lathe.

It’s free to use and share. The thinking behind every number is in my book, Woodturning: Form and Formula.

    1. Choose a starting shape: a bowl, hollow form or goblet.

    2. Type in the finished height and diameter of your piece, in millimetres or inches. Everything else is worked out from those two sizes.

    3. Move the sliders to shape the piece. When a slider sits on a golden proportion, the line under it turns bronze. Red means you’ve moved off the Golden Ratio, which is fine if that’s what your eye wants.

    4. The fullness sliders change how the curves run between the fixed points. Those are set by eye, so play with them until the form looks right to you.

    5. Set the wall thickness. The base follows the wall unless you unlock it, and then you can set it on its own. The dotted line shows the inside of the piece.

    6. Press Print a template to get a single A4 sheet with the drawing, the measurements and a φ beside every golden one. Set the scale in your print dialog to Default or Actual size, and check one measurement with a rule before you trust it.

    7. Reset proportions puts every slider back on the Golden Ratio.Description text goes here

Starting point
Finished size

These are the finished sizes of the piece. The blank you turn it from must be bigger, with enough extra wood to hold it safely in the chuck.

Divisions

The golden stops on each slider come from the golden ladder: φ and its powers, and the divisions you get by applying them again. That is where the proportion comes from. The sliders move freely in between, and click onto a stop as you get close to one.

The fullness sliders are deliberately not on the ladder. They set how the curve travels between dimensions that are already fixed, and that is a matter of eye rather than arithmetic. Slide them freely.

Anything shown in red is not golden. The plain stops, such as half and 1 : 1, are kept so you can see a form with nothing doing any work and judge the rest against it.

Please Read

The Proportion Tool is a design aid. The drawings and figures are a starting point for your own judgement, not a substitute for it.

All sizes are finished sizes. The blank you turn from needs to be bigger, with enough extra wood to hold it safely in the chuck.

The wall and base thickness figures come from proportion alone. Every piece of timber is different, so judge each one on its own merits before you turn it thin.

Printers vary, so a template can come out slightly larger or smaller than intended. Measure it before you cut to it.

You’re responsible for working safely at the lathe. I can’t accept liability for any loss, damage or injury arising from the use of this tool or its templates.