6. V-carving and inlay#

Three operations cut with a pointed tool, and all three work the same way underneath: how wide the cut is decides how deep it goes. A V-bit at the surface cuts wide; the same bit deeper cuts narrower. Every operation in this chapter is an application of that one fact.

V-Carve#

A V-carve makes letters and shapes look carved rather than routed. Instead of a constant-depth pocket with vertical walls, the tool dives where the shape is wide and lifts where it narrows — so a serif tapers to nothing and a corner comes to a crisp point, exactly the way a hand-cut letter does.

Select closed geometry, pick a V-bit or a taper, set Max Depth, and generate. There is no stepover and no strategy: the shape's own width decides the path.

The toolpath runs down the middle of each stroke, following its centreline. Where a stroke is wide the tool goes deep; where it narrows to a serif it lifts to nothing.

The same job simulated. The letters have sloped walls and the serifs come to a point — neither of which a flat cutter can produce.

Max Depth is a limit, not a target. Most of a carve never reaches it; it stops the tool bottoming out in the widest parts of a broad shape. If your letters come out looking flat-bottomed and blunt, that limit is what you're hitting.

The form tells you the consequence of the number you typed — "cuts at most 4.00 mm wide at full depth" for a 90° bit at 2 mm. That is the width-to-depth law stated for your tool, and it is worth reading before you commit: if the widest part of your lettering is narrower than that figure, nothing in the job will ever reach Max Depth at all.

Holes and counters work without being declared. The bowl of an o, the triangle in an A, an island inside a shape — the app reads them off the geometry, the same as a pocket does.

Which bit#

A taper's ball tip means it can enter a stroke narrower than itself and leave a round-bottomed groove instead of refusing the job, which is what makes it good for fine lettering and small detail. A V-bit closes to a true point and is the sharper result.

Remember the two conventions from chapter 3: a V-bit's angle is included, a taper's is per side.

Photo V-Carve#

Rasters a photograph as a field of V-grooves whose depth follows image brightness. Dark areas cut deeper, and because a deeper cut with a V-bit is a wider cut, the dark parts of the picture become broad grooves and the light parts fine ones. Flood the finished board with paint and sand the face back and the image appears in the grooves.

V-bits only — the effect depends on the width-to-depth relationship of a true cone.

Depth is the resolution control#

This is the part that isn't obvious. Line spacing is not a setting — it is the width of the deepest groove, so that the darkest lines just touch and nothing is cut twice. So the depth range you choose decides how many lines there are:

• A shallower carve is a finer one — narrower grooves, more lines, more detail, less contrast.
• A deeper carve has more contrast and fewer, wider lines.

The form shows the resulting groove width range and line count as you change the depths, so you can trade the two off directly rather than guessing.

Inlay#

An inlay fits a plug of one wood into a socket cut in another, so tightly that the seam disappears. It is two operations on two boards, and the geometry that makes it work is worth understanding before you cut anything.

Why V-walls#

If you cut a socket with straight walls and a plug to match, the plug has to be exactly the size of the hole. A thousandth too big and it won't go in; a thousandth too small and you have a visible line all round.

Cut both with the same V angle and the problem goes away. The plug is a wedge, the socket is a matching wedge, and the plug simply descends until the two wall angles meet. Where it stops is where the fit is tight — so you make the plug deliberately too deep, guaranteeing it lands on its walls and never on the floor.

Three consequences follow from that picture, and they explain every field in the form:

1. The walls are the joint. They must be cut with the same tool angle on both halves.
2. The floor must never touch — that is the Glue Gap, and it is what gives the glue somewhere to go instead of holding the joint open.
3. The face is made by planing, not by machining. You press the plug in, let the glue cure, and plane or sand the assembly back to the female board's face. The seam closes as you approach it.

The form#

You generate the two halves separately, from the same drawing:

Invert answers the same question as Invert Pocket: a design inside a field can be read two ways, and only you know which wood is meant to show. The form says which reading it is using in plain words — "the inner shapes are the plug" versus "the field around the inner shapes is the plug" — so you can check it rather than infer it.

Mirror matters because the male board gets flipped over to go in. If your inlay has any handedness — lettering, a signature, anything not symmetrical — the plug must be machined as a mirror image or it will read backwards in the finished piece. Cutting a mirrored inlay the wrong way round is the mistake that costs a board.

Use a V-bit, not a taper#

A cone is its own mirror image, so a V-bit plug and its socket close completely.

A taper cannot. Its ball rounds the foot of the plug wall — the plug's widest end — while the socket's rounding sits at its narrowest, the deep end. Flip them together and those two roundings don't meet at the finished face. The result is a hairline gap right where you'll be looking at it, up to the tip radius wide: about 0.20 mm for a 0.25 mm tip, 0.30 mm for a 0.5 mm tip.

The angle makes no difference — a taper at 20° and at 60° gives the same gap. The plug still seats perfectly well; it just leaves a visible line. The form says so on the tool row.

This is geometry, not a defect. If you want a taper's fine detail somewhere, use it for the V-carving in that chapter section and keep a V-bit for inlay walls.

Next#

• 7. 3D work — machining an STL surface
• 10. Simulating and exporting — checking a job before you cut it