I selected a chunk of my latigo leather for strength. I prepared the leather by rounding the corners so I could cut a continous spiral. I used my old fashioned calipers set to a quarter inch to scribe on the leather. I selected an old scalpel to free hand cut on the scribe line.
I measured the leather on my graded mat - 1 length is 34" I created 7.5 passes so:
7.5 x 34" = 255"
255" / 12" = 21.25'
I also took pics of the leather coiled showing some imperfections in thickness but overall consistant.
Ways I could improve:
Maintain a sharp cutting instrument.
Cut the leather into a better shaped circle.