How big can text be around a cylinder, and why does deep V-carving look squeezed on a rotary job?

What is going on

Two separate things affect lettering on a cylinder.

1. How far around it reaches. In the flat view, distance along the wrapped axis is really an angle. The whole wrapped dimension is 360 degrees. On a 3.5 inch cylinder the circumference is about 11 inches, so one degree is about 0.03 inch and a word 1 inch wide covers roughly 33 degrees. The same word on a 2 inch cylinder (6.28 inch around) covers about 57 degrees. Text that looks modest on screen can disappear around the side of a small part.

2. Compression with depth. The official documentation states that wrapped toolpaths match the flat toolpaths only at the surface of the blank. The deeper the cut (closer to the rotation axis), the more the path is compressed around the cylinder. A V-carve is deepest where strokes are widest, so wide strokes on a small diameter are the ones that change shape.

How to lay it out

1. Work out the circumference (3.14159 times diameter) and decide what fraction of the way around the text may reach. For text read from one side, stay well under half.
2. Decide the reading direction. Text along the length of the cylinder can be long. Text around it is limited by step 1.
3. Keep the carve shallow relative to the diameter: use thinner letter strokes, or cap the depth with Flat Depth (see the entry on Flat Depth).
4. Check in the 3D view with Auto Wrapping on.
5. Zero Z carefully. V-carve width depends on depth, so a Z error changes every stroke (see the entry on rotary parts coming out the wrong diameter).

Pro tips

• Round shapes look oval in the wrapped preview. The official guide notes that the rotary simulation is not fully accurate and that such holes still machine round.
• The surface must be truly round and on center before lettering. Any high side carves wider and deeper there.
• No source gives a safe depth limit for a given diameter. Test your font on a scrap of the same diameter.