Why does my V-carve inlay have gaps, or the plug won't seat all the way? (A common depth recipe)

Why this happens

A V-carve inlay works because both parts are cut with the same V-bit, so the walls have identical angles and wedge together. It fails when:

1. The Start Depth / Flat Depth relationship is misunderstood. In the manual recipe below, the plug's cut depth is built from its Start Depth plus its Flat Depth. Getting these backwards makes the plug bottom out before the walls engage (gaps) or sit proud.
2. No glue gap was left below the plug, so the glue has nowhere to go and can hold the plug up.
3. A different bit, the wrong angle, or bit deflection between the two cuts, so the wall angles no longer match.
4. Machine play or low rigidity, where deflection makes the fit vary from letter to letter.

A common community depth recipe

This recipe is widely shared by CNC woodworkers. It is a starting point to test on scrap, not an official value.

• Female (pocket): V-carve with Flat Depth 0.15", Start Depth 0
• Male (plug): V-carve the mirrored artwork (with the area around it carved away) with Start Depth 0.145", Flat Depth 0.025"

Result: the walls engage over a deep contact area, with about 0.005" glue gap at the floor when seated. This is inside the official range for the VCarve Inlay Toolpath's Glue Gap (0.001 to 0.01 in, or 0.02 to 0.2 mm). Glue, clamp, let cure, then bandsaw or plane off the plug's backing board.

1. Use the identical V-bit for both toolpaths, and verify its true angle with a test cut.
2. If fit varies across the design, take shallower passes (reduce the bit's pass depth in the tool database) to reduce deflection.
3. In V12 and later, the VCarve Inlay Toolpath form creates the pocket and the mirrored plug together from Pocket Depth, Glue Gap and Surface Clearance. The recipe above explains what it is doing and lets you tune it.

Pro tips

• Fine details snapping off the plug during the first pass? Using Flat Depth for the glue gap makes the first cut a deep full-width pass over thin features. Instead, run several V-carve toolpaths stepping Start Depth up in increments no bigger than the pass depth until you reach the target, so every cut stays shallow.
• Test the fit dry on scrap before gluing the real one.