Hex Bolt

Hex Bolt

Hex bolts are used to fasten two or more parts together to form an assembly either because it cannot be manufactured as a single part or to allow for maintenance and repair disassembly. By definition "A Bolt is a headed and externally threaded mechanical device designed for insertion through holes in assembled parts to mate with a nut and is normally intended to be tightened or released by turning that nut." When used with a preformed internally threaded (tapped) hole, the hex bolt's head is turned to tighten.Hex bolts are also known as: hex head bolts, cap screws, hex cap screws, hex head cap screws, machine bolts, hex machine bolts, hex head machine bolts and, if fully threaded, tap bolts, hex tap bolts and hex head tap bolts. A hex bolt is often differentiated from a hex cap screw by its underhead bearing surface: if it has a circular boss, called a washer face, it's a hex cap screw—if it doesn't then it's a hex bolt.

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MATERIALS
Common materials are steel (unplated and plated; see Finishes below), stainless steel, brass, silicon bronze, and nylon. Grade A307 hex bolts are made from low or medium carbon steel as is Grade 2, which is also cold worked; Grade 5 is from medium carbon steel, quenched and tempered; and Grade 8 is manufactured from medium carbon alloy steel, quenched and tempered. Stainless steel, such as 304 and 316, cannot be heat treated. Steel fasteners are magnetic, stainless steel may be slightly magnetic are not made of iron (nonferrous) so they are nonmagnetic. Steel remains the least costly material followed by stainless steel; the copper alloys (such as brass and silicon bronze) are the most expensive.
THREADS and POINT
Hex bolts have either cut or rolled screw threads that comply with the Unified system: UNC (Unified National Coarse) and UNF (Unified National Fine). Coarse threaded fasteners have fewer threads per inch than fine threaded fasteners because coarse threads are farther apart. Consequently, the larger the number of threads per inch, the finer the thread. Also, smaller sizes have more threads per inch than larger sizes—a 1 1/2" UNC bolt, for example, has just 6 threads per inch. Coarse bolts are more common, and there are advantages and disadvantages to both coarse and fine threads. Short lengths are fully threaded while longer lengths follow a standard formula: for bolts 6" and shorter, the threaded length is two times the basic thread diameter plus 1/4", and for lengths greater than 6", two times the diameter plus 1/2". This, however, is the minimum threaded length and manufacturers may thread the bolt substantially more. In addition, some longer bolts are fully threaded and are often called tap bolts. Hex bolts are not pointed whereas hex cap screws have a chamfered (beveled) point to protect the first thread from damage and to facilitate entry into an internally threaded part such as a nut or tapped hole.
Metric Hex Head Bolts have a hex head and coarse or fine machine screw threads. Select from partially threaded or fully threaded. All short lengths are fully threaded; for partially threaded the minimum thread length is longer for larger bolt sizes. JIS B1180 and three sizes of ISO 4014 and ISO 4017 have heads that are smaller than their DIN counterparts. Steel, from Class 4.8 to 12.9, and stainless steel are available as are plain and zinc plated finishes. To differentiate between partial and full threads, we classify Hex Head Bolts as partially threaded and Hex Head Cap Screws as fully threaded. Hex Head Bolts are also called Machine Bolts.

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