#Metal protractor manual#

Gurley, A Manual of the Principal Instruments Used in American Engineering and Surveying, 37th ed. Studiensammlung im Stadtmuseum SchlГ¶ssli Aarau,вЂќ W.

#Metal protractor archive#

AG,вЂќ Virtual Archive of Wild Heerbrugg, вЂњKern & Co. References: Juerg Dedual, вЂњMilestones of Kern & Co. (1836вЂ“1916), and donated by his granddaughter, Margaret van D.

This protractor was owned by the renowned American designer of steam engines, Erasmus Darwin Leavitt Jr. In 1909, Keuffel & Esser sold a similar protractor in a mahogany case for $19.25. The arm was lengthened and squared off in versions sold in the 20th century. The arm also has a blade-like extension three inches long. The number 8 is stamped on the back of the vernier arm. A movable arm attached to the center contains a vernier scale that allows the user to read angles to one minute of arc. A center cross-plate, or horncentre, contains crosshairs to assist with placing the protractor on a drawing. It is graduated along the outer edge to one-quarter degree and engraved by tens from 350 to 0 to 190 in both directions, from left to right and from right to left. The protractor is made of German silver, also called nickel silver. Former employees ensured that 1,700 objects were preserved as the Kern Collection in the city museum of Aarau, Stadtmuseum SchlГ¶ssli Aarau. merged with the Wild Leitz group in 1988, and the plant in Aarau closed in 1991. Its products can be found in the catalogs of many 20th American manufacturers and retailers. in 1885, the firm was highly regarded for its craftsmanship. The makerвЂ™s mark indicates the protractor was produced between 18 in the workshop founded by Jakob Kern (1790вЂ“1867) in Aarau, Switzerland. The case is in very poor condition, but it was originally covered with thin leather and lined with purple velvet. Finally, use the bottom edge of the protractor as a straight edge to draw a line between the two points.Kern Semicircular Protractor Description This semicircular protractor is housed in its original wooden fitted case. Rotate the protractor and line the bottom edge up between the vertex and the small dot. Now, find the hash mark on the protractor that corresponds with the angle you want to draw, and draw a small dot outside of it.

Then, line the bottom edge of the protractor up with the vertex and draw a straight line along it. Draw a small dot in the hole on the protractor to mark the vertex. To draw an angle with a protractor, first place the center point along the bottom edge of the protractor where you want the vertex of the angle to be. If the angle is facing left, use the top row of numbers. If the angle is facing to the right, use the bottom row of numbers on the protractor. Follow the other leg of the angle up to the protractorвЂ™s arc to see what number it intersects with and find the degree of the angle. Line up the bottom edge of the protractor with one leg of the angle. To measure angles with a protractor, first place the center point along the bottom edge of the protractor over the vertex of the angle you're measuring. You can use a protractor to measure and draw angles.