Read inside face distance rather than inside corner radius for staves.
Does the inside ring dimension end at a flat face or a vertex?
Use the matching calculator
Use this decision sequence
- Confirm the supplied ring is a regular polygon with identical staves.
- Use the inside apothem, measured perpendicular to a flat face.
- Apply supplied radial thickness to obtain the outside apothem.
- Read both face widths and retain the shape assumptions with the cut drawing.
Keep the quantities distinct
| Quantity or assumption | How to use it |
|---|---|
| Inside apothem | Centre-to-flat-face measurement. |
| Inside corner radius | A different, longer centre dimension. |
| Stave face widths | Differ between inside and outside because the section is trapezoidal. |
Worked comparison
An illustrative four-sided ring with 1 m inside apothem and 0.1 m radial thickness has inside face width 2×1×tan45° = 2 m and outside face width 2×1.1×tan45° = 2.2 m. Those unequal widths are required by the stated polygon geometry. They do not establish a machine setting or a suitable joint detail.
Check before using the estimate
No support, pressure containment, joint-strength or cutting procedure is specified.
All dimensions, product properties, prices and specifications in this example are illustrative arithmetic inputs. Use the values from your measured plan, selected product data sheet and supplier quote. This guide does not choose construction specifications or certify safety.
Calculation and scope checked 2026-10-04. Methods and scope.