Recently, I finally decided to find out what the 2.5 translated to. The following website explained it all.
http://www.quiltmaker.com/blogs/quil...stitch-length/
For my own clarity, I wrote up the following:
Stitch number is based on millimeters per inch which is 25.4
Divide 25.4 by the machine setting to get stitches per inch.
25.4 / 3 = 8.47 stitch per inch
25.4 / 2.5 = 10.16 stitch per inch
25.4 / 2.1 = 12.1 stitch per inch
25.4 / 2 = 12.7 stitch per inch
25.4 / 1.5 = 16.93 stitch per inch
If you know the stitches per inch you want, the formula is:
25.4 mm / stitches =
25.4 / 10 = 2.5 setting
25.4 / 12 = 2.1
25.4 / 16 = 1.6
The feed dogs control the stitch length. Shorter stitch length equals less fabric pulled thru machine.