Post by Reeper on Aug 8, 2007 0:38:54 GMT -5
Anyone who has worked on trucks has probably been faces with the need for both standard (also known as U.S. or SAE) and metric tools. In a pinch, a 13mm end wrench will loosen a ½-inch bolt head, as long as it isn’t torqued down too tightly. But metric fasteners are different than standard fasteners and should never be interchanged; nor should the tools designed to tighten or loosen them. As more auto manufacturers move toward metric-spec fasteners, the ability to distinguish between the two has become more important.
All bolts are classified according to length, diameter and thread pitch. A standard ¾-13 x 2 ½ bolt is ¾ inch in diameter, with 13 threads per inch, and is 2 ½ inches long. An M18-1.75 x 62 bolt, on the other hand, is 18 millimeters in diameter, with a thread pitch of 1.75 millimeters and is 62 millimeters long. To the untrained eye, the two bolts may look the same, with seemingly identical specifications. They are, however, quite different and definitely not interchangeable. Forcing one into a threaded hole, in place of the other, can cause serious damage.
Metric and standard bolts can usually be distinguished by inspecting the bolt head. Standard bolts have slash marks radiating from the bolt head’s center. These marks designate the grade or strength of the bolt, which in turn tells the mechanic how much torque can be applied. The more slash marks, the more torque that can be applied. Typically, for automotive use, strength/grade designations of 0 through 5 are used.
Rather than using a slash code, metric bolts carry a grade number stamped into the head, the higher the number, the stronger the bolt. Strength/grade designations ranging from the high 9s to the high 10s (e.g. 9.2 or 10.5) are most common in automotive use.
It is important to note that very low-grade (strength) bolts (0 to 2) are often not marked. To identify two similar bolts, measure the thread pitch of each. Also: metric bolt heads are sized in millimeters across the flat sections, while standard bolt heads are sized in inches. A ½ -inch end wrench on a 13mm bolt head will feel sloppy, an immediate tip-off that the bolt is metric.
Consistent with markings on bolts, hex nuts are marked for strength/grade by numbers on metric-class nuts, and dots (instead of slash marks) on standard-class nuts. The greater the number, or number of dots, the stronger the hex nut.
Like metric bolts, large metric studs carry their strength/grade designation on their ends, while smaller studs use a geometric code (a circle, a + sign, and a square to designate progressively higher strength).
www.offroaders.com/info/tech-corner/reading/nuts-bolts.htm
All bolts are classified according to length, diameter and thread pitch. A standard ¾-13 x 2 ½ bolt is ¾ inch in diameter, with 13 threads per inch, and is 2 ½ inches long. An M18-1.75 x 62 bolt, on the other hand, is 18 millimeters in diameter, with a thread pitch of 1.75 millimeters and is 62 millimeters long. To the untrained eye, the two bolts may look the same, with seemingly identical specifications. They are, however, quite different and definitely not interchangeable. Forcing one into a threaded hole, in place of the other, can cause serious damage.
Metric and standard bolts can usually be distinguished by inspecting the bolt head. Standard bolts have slash marks radiating from the bolt head’s center. These marks designate the grade or strength of the bolt, which in turn tells the mechanic how much torque can be applied. The more slash marks, the more torque that can be applied. Typically, for automotive use, strength/grade designations of 0 through 5 are used.
Rather than using a slash code, metric bolts carry a grade number stamped into the head, the higher the number, the stronger the bolt. Strength/grade designations ranging from the high 9s to the high 10s (e.g. 9.2 or 10.5) are most common in automotive use.
It is important to note that very low-grade (strength) bolts (0 to 2) are often not marked. To identify two similar bolts, measure the thread pitch of each. Also: metric bolt heads are sized in millimeters across the flat sections, while standard bolt heads are sized in inches. A ½ -inch end wrench on a 13mm bolt head will feel sloppy, an immediate tip-off that the bolt is metric.
Consistent with markings on bolts, hex nuts are marked for strength/grade by numbers on metric-class nuts, and dots (instead of slash marks) on standard-class nuts. The greater the number, or number of dots, the stronger the hex nut.
Like metric bolts, large metric studs carry their strength/grade designation on their ends, while smaller studs use a geometric code (a circle, a + sign, and a square to designate progressively higher strength).
www.offroaders.com/info/tech-corner/reading/nuts-bolts.htm