Universal Bevel Protractor Overview

Overview

The lecture explains the components, use, and reading methods for the universal bevel (vernier) protractor, a precision tool for measuring angles.

The base serves as the reference surface for angle measurement and attachment point for accessories.
The blade is adjustable and swings around the protractor to line up with the part being measured.
The tool features a main scale (marked in degrees) and a vernier scale for improved accuracy.
The lock nut secures the blade at a desired angle, while the fine adjustment wheel allows precise setting.
A magnifying glass aids in reading the scales.
An acute angle attachment can be added to measure angles smaller than 90°.

The main scale is divided into four 90° quadrants for both clockwise and counterclockwise measurement.
Each division on the main scale equals 1°.
The vernier scale divides each degree into 12 parts, each representing 5 minutes of a degree.
The vernier scale has two sections for clockwise and counterclockwise readings, each numbered from 0 to 60.
Overall measurement accuracy of the protractor is 5 minutes of a degree.

First, read the main scale at the zero mark of the vernier to get the degree value.
Next, read along the vernier in the same direction as the main scale (clockwise or counterclockwise).
Identify the vernier graduation that lines up exactly with a line on the main scale; multiply its position by 5 minutes to get the additional value.
Add the vernier reading to the main scale reading to get the total angle (e.g., 45°45’ or 14°30’).
Always read both scales in the same rotational direction to avoid errors.

Universal Bevel (Vernier) Protractor — A precision instrument for measuring angles.
Main Scale — The primary graduated scale marked in full degrees.
Vernier Scale — A secondary scale that subdivides a degree for finer measurement (5 minutes per division).
Lock Nut — Device used to secure the setting.
Acute Angle Attachment — Accessory for measuring angles less than 90°.
Minute — 1/60th of a degree.