Sunday, September 8, 2013


A protractor is one of the best tools that you want to have on hand when drafting. For drawing any angles other than the basics - 30, 45, 60 and 90 degrees - you want to have a protractor to ensure your accuracy, especially for odd angles like 71 degrees and everything in between. There are three types of protractors: semicircular, circular and adjustable protractors which serve slightly different purposes. All of these types of protractors are made from different materials depending upon what exactly they are going to be used for and how often. Some protractors are available as solid or with the centers cut out. Center cut out protractors are easier to work with than solid ones.

The most common type of protractor you will come across is semicircular with a 180 degree arc. Sometimes these are referred to as half-circle protractors. There are also circular protractors that encompass the full 360 degrees of a circle, but this variety is used much less often and only in very specific instances. The most accurate of all protractors are the true angle adjustable type. Like circular protractors they are capable of measuring a full 360 degrees. They allow you to define and then make even more precise angles in your work. They have a dial and two blades you can rotate to hairline degrees. These protractors allow for accuracy to half of a degree and it can be accomplished with the same ease of creating a 90 degree angle.

Professional protractors are made of more heavy duty material than academic and recreational protractors. Often they are composed of laminated PVC or vinyl while more common, everyday use protractors are typically just hard plastic. For both the semicircular and circular varieties, a cut out protractor is considered to be more convenient than a solid one because they are easier to lift and place for more guaranteed accuracy in producing angles. Protractors made specifically for drafting additionally have more accurate and die-stamped gradations. In general, the smaller the increments of gradations the more accuracy you can produce. The gradations of some of these more advanced and professional protractors are sometimes sandwiched between two laminated plastic sheets so that they do not rub off from frequent use. This prolongs the life of a protractor, so that it will meet all of your drafting needs for years to come.

Both semicircular and circular protractors can be purchased with cut out centers. Cut out protractors will often come equipped with finger lifts as well as beveled edges. All protractors are available in an assortment of sizes. Semicircular protractors can have diameters of six or seven inches with a radius of three or three-and-a-half inches, respectively. Circular protractors are usually either four, six or eight inches across. The adjustable protractors can be several increments between six inches up to twenty-four inches. The thickness of the protractor depends upon its purpose. Professional protractors are usually slightly thicker. Depending upon your needs, you may want to consider different types of protractors.         


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