Originally Posted by
bergerud
Only the board is measured, not the jig. (You can choose to measure the jig width if you want but not the length.)
The jig says under the rollers and on the brass roller at all times.
The board can go anywhere on the sandpaper rails.
The witchcraft to this is having the top surface of the board 1/8" above the sides of the jig. This allows the machine detect the ends of the board. With the head clamped down lightly, the roller switches switch off when the rollers roll from the board down to the sides of the jig. The optic sensor then finds the end(s) of the board. (There is no end of the jig.) After the board has been measured, the head gets properly clamped down. Now as the carving or cutting proceeds, the rollers may roll off and on the ends of the board but the roller switches do not switch now that the head is down. That means that the brass roller never goes offline and is always tracking. (Normally when a roller switches off, the brass roller goes offline.)