ISO 7379 Socket Head Shoulder Bolts
ISO 7379 Socket Head Shoulder Bolts have a cylindrical head, a precision undersized cylindrical shoulder and a short threaded tip with external coarse machine screw threads; the side of the head may be plain or knurled. The head is larger than the shoulder and the threaded tip is smaller than the shoulder. They are internally wrenched using a hex key or hex bit, which allows for installation in a counterbored recess, and are commonly used as bearings and spacers; hex key size is half the shoulder diameter (for a 10 mm shoulder diameter use a 5 mm hex key). Not suitable for high-strength applications, they are available in Class 12.9 plain finish steel without a rust inhibitor. Due to the undercut area between the shoulder and threaded tip, tightening torque must be reduced to a value less than normal for Class 12.9 fasteners (Class 12.9 is manufactured to increase wear resistance of the shoulder). Thread tolerance is 5g6g; right-hand threads are standard. Shoulder bolt sizes are identified as nominal thread diameter-pitch by shoulder diameter by shoulder length; all dimensions are in millimeters. For example, an M8-1.25 x 10 x 20 mm Shoulder Bolt has a metric thread of M8, a thread pitch of 1.25 mm, a shoulder diameter of 10 mm and a shoulder length of 20 mm. The length of a shoulder bolt is the length of the shoulder, measured from under the head, and does not include the threaded tip. ISO 7379 Socket Head Shoulder Bolts are similar to ANSI B18.3.3M.