Guide · November 2026

Router bit size and part spacing for nesting sign letters

The gap between nested parts is not a style choice. It has to be wider than the bit, or two letters share one cut and both come out wrong.

1. Start with the bit

When you cut on the outside of a line, the bit removes a strip as wide as its diameter. Two letters side by side need at least one full bit diameter between them, plus a small safety margin for machine play and bit wear.

1/8" bit: small letters, thin strokes, tight inside corners.
1/4" bit: larger letters and thicker sheet. Faster and stronger, but more material between parts.

Inside corners are never sharper than the bit radius. A 1/4" bit leaves a 1/8" radius, a 1/8" bit leaves 1/16". If the corners must look crisp, use the smaller bit.

2. Set spacing and margin

Part spacing = bit diameter + margin. Start with about 1/16" extra and adjust after a test cut.
Sheet margin: keep parts away from the edge by at least the bit diameter, more if your clamps sit there.
Use the same bit size in the nest and in your CAM program. A nest made for 1/8" and cut with 1/4" will merge letters.

3. Keep small parts in place

Close spacing saves material, but small letters can move once they are cut free. Add tabs or an onion skin in your CAM program, and cut small parts before the big ones.

Common problems

Letters touch or have a nick: spacing was smaller than the bit. Enter the real bit size and nest again.
Too much waste between parts: the margin is larger than you need, or you are using a bigger bit than the job needs.

Enter the bit once, nest every job with the right gap. In NestSigns you type your bit diameter and spacing, and the nest keeps every part apart by that amount on your sheet sizes. Try it free: 20 nesting runs, no credit card. Sign up with your email.
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More guides: How to nest channel letters · Reduce acrylic waste · Nest letters for Easel · FAQ