General bolt torque specifications include proof load, clamp load and tightening torque. Most bolt torque charts also provide the bolt size, grade and material. Some charts also provide the number of coarse or fine threads per inch.
Torque specifications are crucial to choosing the correct bolt. The proof load is the torque to which bolts are tested by the manufacturer. The clamp load is the safe limit to which a bolt can be tightened; it is usually 75 percent of the proof load. Bolt grades in the United States usually adhere to Society of Automotive Engineers or American Society for Testing and Materials standards.