From A Millwrights Guide to Motor/Pump Alignment, Second Edition


On a shaft a keyway is a linear external machined slot which will contain usually half the depth and the full length of the key. Inside the coupling or other shaft-fitting fixture an internal keyway will contain the other half of the key. When the three are properly assembled, neither the shaft nor the fixture can rotate without the other turning round-for-round also.
The key to the left is only partly inserted into the shaft keyway. The key on the right is fully inserted. This shows an overhead and a profile view on the same shaft, although two keys on the same shaft will usually be in axial alignment with each the other.
Knob fitting:
In alignment this would usually pertain to dial indicator jigs and other such paraphernalia normally part of an indicator set. Knob fittings, sometimes called knurled fittings, are the norm rather than the exception.
Knurled fittings:
See knob fitting.

Products & Services
Machine Keys and Keystock
Machine keys and keystock are demountable machine elements that are used to transmit torque from a shaft to a mounted component, such as a gear or pulley. They are usually made of steel or stainless steel and plated with zinc for wear and oxidation resistance.
Knobs (industrial)
Industrial knobs are small, usually round, devices that are designed for use on industrial machinery, electronic components, and metal cabinetry. They are usually made out of metal, plastic, or rubber and are available in a variety of sizes, colors, and finishes.
Control Knobs
Control knobs are used for the control or adjustment of electronic or electrical devices.
Industrial Pins
Industrial pins are varieties of fastening hardware meant to couple, align, mount, assemble, or penetrate two workpieces. The operation of the pin depends on design and employment, but industrial pins can be categorized into several categories, such as: hitch and linch pins; cotter pins and wire clips; spring pins; locating and fixturing pins; and specialty pins.
Shaft Collars
Shaft collars attach to shafts and are used as stop features or targets for devices such as tachometers.

Topics of Interest

The term reverse indicator is synonymous with indicator reverse, reverse rim, and reverse dial. It refers to a method of acquiring lateral offset measurements of two shafts that are approximately...


B Balancing machine: A machine which will rotate the rotating element of another machine at various applicable speeds and indicate that (usually) metal must be added or removed to the effect of less...

Best results for measuring RPM is for the user to fix his eyes on a single reference target a bolt head, keyway, scratch on the shaft or to place a reference mark such as tape, paint or chalk on a...

Geometric Features This section will define some geometry that is relevant to alignment. Each term will be defined and its engineering symbol shown in accordance with American National Standard ANSI...

Motors and gearboxes that generate high torque and acceleration may make shaft keys obsolete. Designers should analyze stresses and backlash when weighing keyed versus keyless shafts. Stresses in the...