Segmented Turning Calculator — Segment Angles & Sizes

The mitre angle is 180 divided by the number of segments per ring. For 12 segments: 15 degrees. For 8 segments: 22.5 degrees. For 6 segments: 30 degrees. This is the angle on each end of each segment. Two adjacent segments together form the polygon interior angle.

12 segments per ring is the most common choice. It gives a good balance of detail and ease of cutting (15 degree mitre angle). 8 segments are easier but more visible. 16 or more segments create a smoother appearance but require more precision.

Accuracy is critical: 0.5 degree errors accumulate around the ring. Use a precision mitre sled or disc sander with an adjustable fence. Cut all segments slightly oversize, then sand to exact angle on a disc sander with a stop block. Check by dry-assembling the full ring.

Segments should be at least 5mm thicker than the final wall thickness after turning. For a vessel with 6mm walls, cut segments from 12mm stock. This gives a minimum of 6mm for turning plus waste. Thicker segments allow for more design flexibility.