DIN 931 Hex Head Bolts
DIN 931 Hex Head Bolts have a hex head, external machine screw threads and are partially threaded with coarse threads. These externally wrenched bolts are used with nuts and internally threaded holes. Dimensionally similar to ISO 4014, they are available in Class 8.8, 10.9 and 12.9 steel; in stainless steel, most are Class 70 (A2-70, A4-70), some are Class 80 (A4-80) and some uncommon sizes may be Class 50. Zinc plating offers corrosion protection for steel while plain finish lacks a surface treatment to prevent rust. A2 stainless steel is equivalent to 18-8 and A4 is comparable to 316. Also referred to as hex head cap screws, minimum threaded length is based on bolt diameter and bolt length. Thread tolerance for Class 8.8 and 10.9 is 6g for plain finish and 6h for plated; it is 6g for stainless steel; right-hand threads are standard. Measure bolt length from under the head to the tip. DIN 931 Hex Head Bolts are similar to ISO 4014, JIS B1180 and ANSI B18.2.3.1M. Use DIN 933 if you need fully threaded or DIN 960 for partially threaded with fine threads. (Note: Thread pitch, which is the distance from thread to thread, is usually not specified for coarse threaded fasteners but is listed for reference.)