Introduction The most popular thread used in fastening is the machine screw thread. The machine screw thread has a 60 degree thread angle made in a continual running helix pattern. All fastener threads have five defining dimensions, they are the major diameter, minor diameter, pitch diameter, flank angle and pitch. Feature Male Thread Female Thread Major Diameter This is the diameter across the crest of the thread. It is easily checked with calipers. This is the diameter across the root of a female thread. This diameter is very hard to measure and is best checked by a thread gage. Minor Diameter This is the diameter across the root of the thread. The easiest way to check this simnsion is with an optical comparator. This is the siameter of the through hole of the female thread. It can be easily checked with a pin gauge. Pitch Diameter This is the mid point between the crest and root of the thread. It is check by using a pitch micrometer. This is the mid point between the crest and root of the thread. It is check with the use of a thread gague Flank Angle This is the angle made by the intersection of the two thread flanks. It is best checked with an optical comparator. This is the angle made by the intersection of the two thread flanks. It is best checked with a thread gauge. Pitch This is the distance between two consecutive thread crests. It is best checked with an optical comparator. This is the distance between two consective thread crests. It is best checked with a thread gauge. Tolerances A fastener with a machine screw thread can have one of three thread tolerances, they are “ Class 1”, “ Class 2”, and “ Class 3”. The tolerance is called “ Class of Fit”. To indicate that a thread is a male thread an “ A“ is placed behind the Class of Fit number for example 2 A. To indicate that a thread is a female thread a “ B” is used, for example, 3 B. Class 1 Is a very loose fit. It.
find products with these words: You are here: Home > Screws A screw is an externally threaded fastener capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread, and of being tightened or released by torquing the head. An externally threaded fastener which is prevented from being turned during assembly and which can be tightened or released only by torquing a nut is a bolt. ( Example: round head bolts, track bolts, plow bolts.) Additionally, any externally threaded fastener that has thread form which prohibits assembly with a nut having a straight thread of multiple pitch length is also defined as a screw. ( Example: wood screws, tapping screws.) Screw Types Some basic information regarding screws that Aspen Fasteners offers from inventory. Dowel screws A double ended fastener with two tapered and threaded ends often used in furniture manufacturing to create a hidden joint. Half the length of the dowel screw is driven into each of the two pieces making up the joint. Available in zinc plated steel and up to 6 in length. Drywall/framing Screws These screws are specialty drywall & framing screws and are designed specifically for use in drywall applications. The bugle head style, sharp point and threading of these screws are made to attach drywall to wood or metal studs and provide the greatest holding power in drywall. Available in hardened steel with a black phosphate finish and with either phillips or square drives. Eye Screws Also known as screw eyes - a wire form with a looped head and threaded end tapered to a point. Larger ones are often referred to as lag eye screws. Designed to be used as attachment point, particularly for something that is hung from it. Available in zinc plated steel. Hi- Lo Self Tapping Screws These specially threaded screws designed to cut threads as they are driven into.
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