A/F: Across flats. Used when measuring a Hexagonal socket, nut or bit. The measurement is the dimension from one flat side to the opposite flat side.
ACCURACY: Deviation with acceptable limits of a specified standard or tolerance.
ACCURACY, FULL SCALE: When accuracy is measured in terms of a gauge or wrench full scale. Maximum deviation is determined by multiplying the maximum reading by the stated full-scale maximum. Add or subtract the result from the maximum full-scale range to determine the accuracy range of the instrument. For example, a torque wrench has a maximum reading of 100 lbf.in with an accuracy of +5% of full scale, then at 100 lbf.in; an acceptable tolerance range would be 95-105 lbf.in. In addition (using the same wrench) at 10 lbf.in an acceptable tolerance would be 5-15 lbf.in. Remember that to determine accuracy of full scale, always multiply the full scale started accuracy by desired torque value to determine the allowable tolerance.
ACCURACY, READING/SETTING: When accuracy is measured in terms of gauge or wrench reading or setting. Maximum deviation is determined by multiplying the reading or setting by the stated accuracy. Add or subtract the result from the reading or setting to determine the accuracy range of the instrument. For example, if a torque wrench has a maximum range of 100 lbf.in with an accuracy of +3% of reading, then at 100 lbf.in an acceptable tolerance range would be 97-103 lbf.in. In addition, (using the same wrench) at 10 lbf.in an acceptable tolerance would be 9.7-10.3 lbf.in. Remember that to determine accuracy of reading or setting, always multiply the stated accuracy by the desired torque value to determine the allowable tolerance.
BIDIRECTIONAL: Tool that operates with its slated accuracy or repeatability in both right (cw) and left (ccw) directions.
CERTIFICATION: Declaration that an analyzer or gauge gives the appropriate reading (within tolerance). The analyzer is tested with dead weights that conform to NIST specifications to insure the readings that the analyzer shows (when operated properly) are within the stated tolerances of the actual torque.
CLOCKWISE (CW): Right-hand direction.
COUNTERCLOCKWISE (CCW): Left-hand direction. FRICTION: Resistance to relative motion between two bodies in contact.
JOINT: The makeup of two or more elements in a fastening assembly.
DYNAMIC TESTING: Measurement of torque while tool is tightening the fastener.
JOINT, HARD (ISO 5393): Final torque is reached in turning the fastener approximately 30 degrees after it has reached snug level.
JOINT, SOFT (ISO 5393): Fastener has to be tightened more than two complete turns (720 degrees) before final torque is achieved.
LBF: Pounds of force, which are described in inches or feet.
LINEARITY: The extent to which a measuring instruments response varies within its measured quantity range.
NIST: National Institute of Standards and Technology.
OZF: Ounces of torque, which is described in inches.
PRESET: To set tool at desired value and lock or seal it to prevent alteration of setting.
PRODUCTION TOOL: Generally, but not necessarily, a tool that is set or preset to one torque value and sealed for production line use.
REPEATABILITY: The extent to which repeated cycles of a tool produce identical cycles.
SENSOR: A device that changes one kind of stimulus (e.g. electricity) to another (e.g. torque).
SERIALIZATION: Numbering of dead weights or tools to allow for traceable certification.
SI: Sets of torque measurements using Newton’s and meters. Recognized as the International Standard by the International Standards Organization (ISO).
STATIC TESTING: Torque is measured on the fastener after it has been tightened.
STRAIN GAUGE: A plastic film with an etched resistor bonded to a mechanism to be torqued. Its resistance, which can be accurately measured and displayed, changes as torque changes.
TENSION:
A straight-pull force producing stretching of a bolt or screw. Tension is achieved when torque (turning or twisting force) is applied to the fastener.
