![]() Torque wrenches are simply tools for measuring resistance to rotation. It is possible to convert between the various systems: The units given on the torque table here will be in inch-pounds. ![]() Because it can become confusing, it is best to stick to one designation. It is possible to convert between the two units by multiplying or dividing by twelve. Another torque unit used in the USA is the foot-pound (abbreviated ft-lb.), which is the force in pounds along a one-foot long lever. It is possible to convert between the various systems.Īlso sometimes used in the United States is the inch-pound (abbreviated in-lb.).This is a force of one pound acting at the end of a lever (wrench) that is one inch long. Another unit sometimes seen is the Kilogram-centimeter (abbreviated kgf-cm), which is a kilogram of force acting on a lever one centimeter long. One Newton meter is a force of one Newton on a one meter long lever. In the bike industry and elsewhere, the common unit used to measure torque is the Newton meter (abbreviated Nm). ![]() Torque is measured as a unit of force acting on a rotating lever of some set length. In other words, the more effort it takes to tighten a bolt, the tighter it is. Generally, the higher the rotational resistance, the greater tension in the threaded fastener. This resistance can be correlated to, but is not a direct measurement of, fastener tension. Torque for mechanics is simply a twisting or turning motion around the axis of the thread. This means the weakest part of the joint determines the limits of tension, and hence, torque. As a simple rule of thumb, any fastener should be tightened as tight as possible without failure of the thread or the component parts. Vibration, stress, use, or abuse cannot typically overcome the amount of clamping force in a properly sized and secured threaded fastener. However, the common cause for threaded fasteners loosening is simply lack of tension during initial assembly. It is commonly believed that bolts and nuts often come loose “on their own”, for no apparent reason. For example, a fully tightened crank bolt can provide over 14,000 Newton force (3,000 pounds force) as it holds the arm in place. ![]() The amount of pressure applied by a thread can be substantial in order to hold the joint secure. The crank-to-spindle interface receives quite a lot of stress, making larger threads (M8, M12, M14) a better choice. Even if the bolt were as tight as possible, it would not provide enough force to hold the arm secure to the spindle. For example, the M5 bolt of a water bottle cage bolt would not be a good choice for holding a crank. Generally, engineers will specify a thread size large enough to handle the anticipated stresses. Tension in the fastener depends largely upon the amount of torque, the tightening, and the size of the thread. Loose bolts and nuts are also generally the source of various creaking on the bike. This can damage components, such as a crank ridden with a loose mounting bolt. Too little preload will mean the fastener will loosen with use. Too much tightening will deform the threads or the parts. Each fastener is designed for a certain range of tension. ![]() This stretching is not permanent, but it gives the joint force to hold together, called “preload,” or tension. As a fastener is tightened, the fastener actually flexes and stretches, much like a rubber band. Symbols, abbreviations, or full names for units of length,Īrea, mass, pressure, and other types.Threaded fasteners, such as nuts and bolts, are used to hold many components to the bike. You can find metric conversion tables for SI units, as wellĪs English units, currency, and other data.
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