Measuring Curves

[JHCC]

Some classic methods for measuring curves in a drawing or on a curved workpiece:

1. Step off 1” intervals (or whatever unit is appropriate for the particular piece) with a pair of dividers.

2. Use a dressmaker’s flexible tape measure. (Make sure that the workpiece isn’t hot, or it could melt or burn the tape.)

3. Lay a length of string along the curve, mark the ends of the curve, straighten the string, and measure between the marks. 

3a. The same thing can be done with copper or iron wire or a coil of solder. 

And here’s a new one, a variation of the classic wheelwright’s traveller: If you have a pizza cutter with a 2-3/4” wheel, its circumference is close enough* to 8-5/8” as to not make a difference in shop conditions.

Just make a mark on the edge of the wheel so that you can count the revolutions. 

 
* 8.639” vs 8.625”, less than 1/64” difference.