My rotary blank is a rough log or out of round. What diameter and Z zero should I use?

Why uneven stock is a problem

The software assumes a perfect cylinder of the Diameter you enter. A real blank that is tapered, bowed, square or chucked off center has high spots the software does not know about. The first pass can bury the bit in a high spot, and low spots can be left uncut.

What to enter

1. Diameter: enter the cylinder you will end up with, which can be no larger than the thinnest part of the blank. A published machine-maker example: a log that is 6 inches at its widest and 5 inches at its narrowest is set up as 5. Another tutorial sizes a rough 5 inch log as 4.5 to clear surface defects.
2. Length: less than the real blank. The same guide leaves about an inch at each end of a 48 inch log (job length 46).
3. Z zero: the official documentation recommends the cylinder axis for every rotary job, because the center stays put no matter how irregular the surface is.
4. Round the blank first. The rounding gadget asks separately for the raw blank size, so it starts high and works down (see the entry on rounding a square blank).
5. For a very uneven log, a raster rounding pass is the gentler choice. Some passes cut air, but no single pass goes deep.

Where sources differ

One machine-maker guide suggests zeroing Z on the surface at the thickest point of an unrounded log, so early passes cannot plunge deep. The official documentation says to use the axis. Both protect the bit as long as the rounding toolpath knows the true raw size. Follow the official method unless your machine's own guide tells you otherwise, and never mix the two in one job.

Pro tips

• Raise Clearance (Z1) in Material Setup so rapid moves clear the corners of square stock while it turns. The software works from the cylinder diameter you entered, so give the corners extra room.
• Open the saved file before running it. If the cutting moves sit at Z 0.000, the raw size and finished size were entered wrong.
• Put the thicker end of a tapered blank at the motor end.