VTube-LASER Bend Profile Radius Calculation Accuracy Principles and the Radius Average Calculator

Updated at January 28th, 2026

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Table of Contents

The Caveat for Calculating Bend Radii Values Principle: As the bend angle approaches zero, the ability to calculate its radius value accurately from surface points is reduced geometrically. The Application and Solution of the Principle of Diminishing Accuracy in Radii Calculations Video Showing How It Works Document Explaining Principles

The Caveat for Calculating Bend Radii Values

Measuring and reporting a bend profile from the surface points of a bend is a simple process. However, bend radii cannot be directly measured (like surface points can). A radius is a calculated value derived from measured surface points. The calculation is dependent on the limitations of mathematics for angles. Therefore, calculating a bend's radius from the same surface points of a bend comes with important caveats

Principle: As the bend angle approaches zero, the ability to calculate its radius value accurately from surface points is reduced geometrically.

Assuming a system can scan surface data at 50 microns (0.002 inches), the following is true for calculating radius values:

Bend Angle	Measuring Center Accuracy	The radius calculation accuracy diminishes by...	Radius Calculation Accuracy MM	Radius Calculation Accuracy IN
90	0.050 millimeters, 0.002 inches	3 times	0.15	0.006
45	0.050 millimeters, 0.002 inches	16 times	0.80	0.031
20	0.050 millimeters, 0.002 inches	80 times	4.00	0.160

The Application and Solution of the Principle of Diminishing Accuracy in Radii Calculations

1 - While it can be useful to reverse-engineer a part's radius to determine what tool to use on a bender, bend radius qualifications are of limited value in metrology. A better method for radius qualification is to qualify the surface profile for the bend without reference to a calculated radius.

2 - The best solution for calculating a radius is to use the VTube-LASER RADIUS AVERAGE CALCULATOR (available as of version 4.3 build 1570, May 2024). This calculator stores and averages multiple scans of a single radius to give VTube the average radius within the variance created.

Video Showing How It Works

Document Explaining Principles

See the document to learn why radius averaging is necessary to solve variations in radius calculations for shallow bends. 20240507 Radius Calculation Accuracy Principles.pdf

The images below are from the PDF document.