DIN 7991 Flat Head Socket Cap Screws
DIN 7991 Flat Head Socket Cap Screws are internally wrenched (hex socket) countersunk-style with external machine screw threads, a flat top and cone-shaped bearing surface. The head angle is 90° for M20 and smaller and 60° for M22 and larger (inch series screws are 82°). When mounted in a matching countersunk recess the top of their head will be flush with the mounting surface. Select from Class 10.9 zinc plated and plain finish (no rust protection) steel and stainless steel. Thread tolerance is 6g; right-hand threads are standard. NOTE: They are manufactured in Class 10.9 (and above) to increase wear resistance of the hex socket recess—head geometry reduces loadability and prevents them from being used in high-strength applications (see ISO 898-1). The length of flat head screws is measured from the top of the head to the tip. DIN 7991 Flat Head Socket Cap Screws are similar to ISO 10642 and ANSI B18.3.5M.