What should my first rotary project be, and what mistakes ruin a first rotary job?

A sensible first project

Keep it small, soft and short so mistakes are cheap. One machine maker's starter project is a chess piece in softwood: a blank about 1 inch in diameter and 3 inches long, held in the chuck with no tailstock, cut with a single 3D finishing toolpath and a 1/4 inch tapered ball nose. They run it deliberately slowly, about an hour, so you can watch.

If you have no 3D model, the official guide's first exercise is a plain column: two ring cuts with a Profile Toolpath and 8 flutes with the Fluting Toolpath.

Order of operations

1. New job, type Rotary. Enter Diameter and Length, set Z zero to the cylinder axis, choose the Orientation that matches your machine.
2. Put the XY datum at the chuck end.
3. Make the job shorter than the blank so the bit cannot reach the jaws.
4. Create one simple toolpath and preview it. The preview plays flat, then switches to the wrapped view.
5. Save with the wrapping post-processor for your machine.
6. At the machine: zero Z to the rotation center, zero the length axis clear of the chuck, set the rotary zero.
7. Run an air cut first (no bit, or well above the stock) and watch which way things move.

Mistakes that ruin first jobs

• Wrong post-processor. A flat post never turns the part. A wrap post for the other axis can send the machine into its limits. One public owner thread traced soft-limit errors and a wrong diameter to exactly this.
• Z zero mismatch. The job says axis, the machine was zeroed on the surface (or the reverse).
• Job as long as the blank. The bit meets the chuck or the faceplate screws.
• No holding stock or tabs. The piece comes free before the cut ends.
• Poor model orientation. Anything the tool cannot see from directly above the axis stays uncut.
• Bumping the rotary axis during a bit change. The second toolpath is then rotated out of register.
• Not reading the file. A quick look should show rotary moves that end at 360 degrees for a full wrap.

Pro tips

• Skip roughing only on tiny soft blanks. Larger work needs a roughing pass first (see the entry on rotary 3D roughing).
• Round square stock before carving (see the entry on the rounding gadget).
• Ovals in the wrapped preview are a display effect, not an error.