---
title: Technical Paper | Tolerancing | Spherical Radii | Optimax
description: This Technical Paper from Optimax Systems is a review of Tolerancing schemes for Spherical Radii, including the historical origins. Click here for free access.
---

#### Technical Paper

# Tolerancing, Specifying and Measuring Spherical Radius

## Rick Plympton

# What's it about?

### This paper will review tolerancing schemes for spherical radii, including the historical origins. It finishes with recommendations for specifying tolerances for spherical radii.

## 1. POWER TOLERANCE VERSUS RADIUS TOLERANCE

There are two main paths for tolerancing spherical radii: power tolerance and linear radius tolerance. Both measure change relative to a nominal value, but the metrology used is the key difference.

Power Tolerance: Controls radius through increments of sag change relative to a test plate of known radius. The sag difference between the known radius and the surface under test is measured, from which the radius of the surface can be calculated... 

## Get the paper here

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