Peak to Peak

The sum of the maximum and minimum amplitudes shown on a sine curve. See sine wave.

Peak Spectra

A frequency domain measurement where, in a series of spectral measurements, the one spectrum with the highest magnitude at a specified frequency is retained.

Peak Hold

A menu choice on data collectors. The data collector will continuously collect data and as the amplitude varies, will capture and hold the latest peak amplitude. This will continue until the data collection is halted.

Potential unbalance

The maximum probable net unbalance of a coupling after installation. Potential unbalance results from a condition of the residual unbalance of individual components and subassemblies and possible eccentricity of the components and subassemblies due to runout and tolerances of the various surfaces and registers. The numerical value of the potential unbalance is the square root of the sum of the squares of all the contributory unbalances. Typical contributory unbalances are (1) the residual unbalance of each component or subassembly, (2) errors in the balance of each component or subassembly resulting from eccentricity in the fixture used to mount the component or subassembly in the balance machine, and (3) the unbalance of each component or subassembly due to eccentricity resulting from clearance or runout of the relevant registers or fits.

Parallel offset misalignment

The lateral distance between the centerlines of two coupled shafts that are parallel but not in the same straight line.

Peak torque rating

The torque rating that corresponds to a minimum factor of safety of 1.15 with respect to the component’s material yield strength, expressed as a combination of speed, angular misalignment, and axial displacement.

Pilots (Rabbets)

Surfaces that support a coupling component, subassembly, or assembly upon which another coupling component is mounted or located.

Pin-and-bushing coupling

A coupling that consists of two flanged hubs with pins on one flanged hub fitting into bushings in the mating flanged hub.

Polar mass moment of inertia

The measure of resistance to a change in rotational velocity about an intended rotational axis. It can be derived by dividing the flywheel effect WR2 by the acceleration due to gravity: J = WR^2/g (Ib-ft/sec^2), where R is the Radius of gyration (ft), W is the weight (lb), and g = 32.2 ft/sec^2.

Press Quenching

A quench in which hot dies are pressed and aligned with a part before the quenching process begins. Then the part is placed in contact with a quenching medium in a controlled manner. This process avoids part distortion.