Thus the normal scales of British maps can be drawn from the protractor. The Service Protractor Mark IV shows scales of ¼ inch and 1 inch to the mile also scales for R/Fs of 1/25,000, 1/50,000 and 1/250,000. It is made of celluloid by Reeves & Sons Ltd of London and in addition to the angles around the edge has multiple lines for different scales of maps on both sides: The 1929 copy of ‘Notes on Map Reading’ explains about the scales: This mark of protractor seems to date from the 1920s- the Mk IV was introduced in about 1930. This example, although not /|\ marked, is one issued to British Army Officers: This example is marked ‘Protractor Rectangular ‘A’ Mk III’ (6”x2” Exactly). To accurately plot a position on a map or to draw a map from scratch, the ability to transfer bearings onto the page is essential and for this a protractor designed to be used with military maps is very helpful. Whether it is to navigate to an enemy position, design a bridge or bring down artillery fire maps are used every day by the armed forces. Some protractors have a satin chrome finish to improve the visibility of the scales.The importance of maps to the military can scarcely be underestimated. Bevel protractors are often ground and made from stainless steel. Bevel protractors are designed for making high-precision measurements and are commonly used for producing mechanical and architectural drawings and by tool makers. As with the regular protractor, the Vernier scale is bidirectional and can be read to either side. The Vernier scale has 24 divisions with 12 divisions on either side of 0 with each division representing 5 minutes. The fixed dial or main scale has four sections with each one graduated from 0 ° to 90 °. Bevel protractors are more accurate than regular protractors as they use a Vernier scale along with a fixed scale. There are variants of this design including a universal precision protractor and a precision universal Vernier protractor with a more technical design. The construction of a bevel protractor consists of a beam, a graduated dial and a blade which is connected to a swivel plate by a thumb nut and clamp. The Vernier scale is found underneath the main degree scale and is spaced so it reads at a constant fraction of the fixed main scale.Bevel Protractors:These are able to measure through 360° by using one or two swinging arms that can help measure the angle. In the Vernier scale, each graduation represents 0.02 mm or 1/12 of a degree. This type of protractor is commonly used in classrooms for geometry and in mechanical and engineering-related applications.The Vernier Scale:This is used on protractors to enable them to give more precise and accurate measurements. The semi-circular protractor is used for reading, drawing and plotting angles on paper or charts. On the base of the protractor is a midpoint mark that indicates the position of the highest point of the angle that is going to be measured or the vertex. More durable and typically higher quality protractors can be made of metals such as aluminium or Stainless Steel.Types of ProtractorSemi-Circular Protractor:This protractor has two sets of scales graduated up to 180° in opposite directions enabling angles to be read from two directions. Protractors A protractor is a mathematical instrument often made from clear plastic used for measuring angles in degrees such as the angles of a triangle or a hexagon.
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