# Glossary

Parameter | Definition
--- | ---
Angle correction | When the joint design or space limitations preclude use of standard sockets or tools, it may be necessary to use special extension spanners to fit the application. When an extension is used, the angle correction constant permits linear compensation of extension torsion due to the torque applied. It is a fixed additive value. The value is expressed in degrees at the reference torque (Torque nominal).
Batch size | This parameter specifies how many times the test must be executed. Inside an inspection, this is the number of results expected to complete the inspection.
Breakaway threshold | It specifies the maximum angle for the residual torque (measured from the Start Final Angle). Over this angle the test result is marked as “not detected”.
Change screw at | Over-torque threshold that generates an alarm during the test if passed. The alarm notify to the operator that the over-torque applied has damaged the screw. The screw replacement is recommended. This must be higher than the Final Torque max value.
Cm index | The Cm index describes machine capability; it is the number of times the spread of the machine fits into the tolerance width. The higher the value of Cm, the better the machine.
Cmk index | The Cmk index describes the capability corrected for position. It is not much use having a high Cm index if the machine setting is way off center in relation to the middle of the tolerance range. A high Cmk index means, then, that you have a good machine with a small spread in relation to the tolerance width, and also that it is well centered within that width. If Cmk is equal to Cm, the machine is set to produce exactly in the middle of the tolerance range.
Cp index | The Cp index describes process capability; it is the number of times the spread of the process fits into the tolerance width. The higher the value of Cp, the better the process.
Cpk index | The Cpk index describes the process capability corrected for position. It is not much use having a high Cp index if the process setting is way off center in relation to the middle of the tolerance range. A high Cpk index means, then, that you have a good process with a small spread in relation to the tolerance width, and also that it is well centered within that width. If Cpk is equal to Cp, the process is set to produce exactly in the middle of the tolerance range.
Cycle complete | When the torque goes and remains under this value for longer than the End cycle time parameter, the test ends (click wrench).
Cycle start | Torque value from which to start the torque measurement. This must be higher than the transducer Minimum Load value.
End cycle time | This timeout defines the end of the test.
Filter frequency | Filtering is a digital operation done on the torque values in order to reject measurement noise and to improve the quality of the measurement results. The filter frequency is a value that gives an indication of what the data collector “ignores” from the process it is monitoring. This value should be chosen carefully: a value that is too small (for example 10 Hz) produces a not correct result for the fast tests made on power Tools. On the other hand, a value that is too large (1000 Hz) can be responsible for noisy traces and results.
Final angle monitoring torque | For control strategies involving angle measurement, it specifies the torque value from which the angle measurement starts.
Free round | Free rounds before starting the braking; used for some screwdrivers requiring a number of free rounds to reach the proper operating speed before starting the test operation.
Friction coefficient | Dimensionless scalar value which describes the ratio of the friction force between two bodies and the force pressing them together. The coefficient of friction depends on the materials used.
Measure delay time | This timeout is used to filter the possible spikes or noise at the beginning of the test. When the torque reaches the Cycle Start value, the timer starts. During this interval the torque is not considered.
Measure torque at | Point at which the torque value is measured. The two options are: torque peak or angle peak. It defines which value to acquire on the curve as torque result, if on the local max torque or angle at the end of the curve.
Minimum pulse | Minimum pulse to calculate the Cm-Cmk related to the number of pulses per second.
Maximum pulse | Maximum pulse to calculate the Cm-Cmk related to the number of pulses per second.
Ratchet time | Applied instead of the End cycle time when the torque goes below the cycle start but has not yet reached the Minimum torque value. This allows the operator to release the torque for a while and recharge during the test operation.
Relaxation time | Due to the mechanical relaxation of the wrench, the torque peak detected by the wrench slightly decreases after a short time interval. This parameter allows to adjust the peak detection in case of wrenches that do not save the torque peak, thus reducing discrepancies between the transducer and the wrench torque peak detections.
Reset time | This timeout is used to filter the possible spikes/bounces after the click-point. When the torque goes below the cycle complete value, the timer starts. During this time the torque trace is not analyzed (any click-point possibly occurring during the reset time is not considered).
Residual angle threshold | It specifies the maximum angle (measured from the Start Final Angle) for the residual torque when a the residual torque is lower than the breakaway point.
Slip torque | The slip torque gives the requested drop in torque after the click-point. If the torque drops more than the slip torque, the peak value is considered as click-point; if not, the peak value is ignored.
Subgroup size | This parameter defines the number of tests (subgroup) necessary to define each point (the average value of the tests in the subgroup) of the SPC charts.
Subgroup frequency | SPC, the points shown on the X-R chart are the averages of the set of tests defined in the Subgroup size parameter. The Subgroup Frequency parameter defines the frequency of the points considered in the chart and in the SPC rules: Subgroup Frequency = 1 → all the points are considered. Subgroup Frequency = 2 → one point every 2 points is considered. Subgroup Frequency = X → one point every X points is considered.
Torque correction coefficient | When the joint design or space limitations preclude use of standard sockets or tools, it may be necessary to use special extension spanners to fit the application. In these cases, the wrench measure must be adequately compensated because the factory calibration is made for the standard arm and the extension arm increases the measured torque. The angle measure is also affected by the extensions, due to its specific torsion when the torque is applied.
Torque threshold | Limit of the torque value.
Yield point | Increasing a torque on a joint, this is the point at which the elastic behavior ends and the plastic elongation begins.
Yield stress point | Theoretical point of stress (pressure) beyond which the material loses its elasticity and becomes permanently stretched.

## Applies to: