Kerf

Kerf is the width of material that a cutting tool removes. On a CNC router it is the bit diameter; on a laser it is the width of the burned line.

Typical kerf sizes

Tool	Kerf
CNC router, 1/8 in bit	0.125 in (3.2 mm)
CNC router, 1/4 in bit	0.25 in (6.35 mm)
CO2 laser on acrylic	about 0.004–0.01 in (0.1–0.25 mm)
Table saw blade	about 1/8 in (3 mm)

These are typical values. The real kerf also depends on bit wear, runout, material and feed rate, so many shops cut a test square and measure it.

Why kerf matters for sign letters

Part spacing. When letters are cut next to each other, the gap between them has to be at least the kerf, or the bit cuts into the next letter. Most shops add a little extra so the bit never touches the neighbor.
Size of the part. CAM software offsets the toolpath by half the kerf (outside for letters, inside for holes) so the finished letter matches the artwork.
Faces and backs that must fit. For channel letters, the face, back and trim must match. A wrong offset makes every piece a little too big or too small.

How NestSigns handles it

Type your bit diameter and NestSigns sets the spacing between parts from it, a little more than the bit. After nesting, every layout is measured and the smallest gap is shown, so you can see the spacing is wide enough before you cut. The toolpath offset itself is set in your CAM software.

Try it on your own job. Open your artwork, pick a sheet, and see how many sheets you need. 20 free nesting runs, no credit card. After that, $14.99 per month, cancel anytime.
Start free