What is the mitre angle for segmented turning?

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.

How many segments per ring is best?

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.

How do I get tight joints in segmented turning?

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.

How thick should segments be?

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.

WoodCalcs

Segmented Turning Calculator — Segment Angles & Sizes

Calculate segment angles, ring diameters, and piece counts for segmented turning.

Finished Diameter

Finished outer diameter of the turned ring/vessel; the turning allowance is added to size the glue-up blank

Segments Per Ring

Ring Thickness

Radial wall depth of each ring (inner-to-outer); width waste is added to set the segment width

Number of Rings

How We Calculate This

This calculator computes segment dimensions for building rings that will be glued up and turned on a lathe.

Key formulas

Mitre angle = 180 / Number of segments

Segment outer edge = 2 x R x tan(pi / n)

Where R = outer radius of the ring and n = segments per ring. The tangent (circumscribed) edge ensures the glued-up polygon fully encloses the finished circle; the chord (2 x R x sin) would leave the flats inside the nominal diameter and eat into your turning allowance. Ring outer diameter is the finished diameter plus the turning allowance (default 20mm). Segment width is the radial wall depth of the ring plus the width waste (default 5mm) for flattening and truing.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify measurements and material quantities before cutting or purchasing.