Keyed Shafts.

What are Keyed Shafts?

Keyed shafts, also known as keyed rotary shafts or keyseated shafting, are a core component of Accu's linear and rotary components range, machined with a longitudinal keyway that locks rotating components to the shaft so torque transfers without slip. Each shaft is a straight, precision ground cylindrical bar with a rectangular slot milled along its surface, sized to accept a matching parallel key that sits half in the shaft and half in the hub of the component mounted over it. That mechanical interlock removes any reliance on friction alone, giving a positive drive connection that holds its position under reversing loads, shock starts and continuous high torque.

Every keyway is milled to an established dimensional standard, ANSI B17.1-1967 on imperial shafts and DIN 6885-1 on metric shafts, so keys and hubs with a matching standard drop straight in. That interchangeability makes keyed shafts a dependable choice for power transmission across automation, robotics, conveying and general machine building, where a predictable drive interface matters as much as the torque rating itself.

How Keyed Shafts Work.

Installation starts by sliding the mating component, typically a gear, pulley, sprocket or coupling, over the shaft until its own keyway aligns with the slot in the shaft. A parallel key is then fitted into the combined pocket, filling the gap between shaft and hub, and the component is located axially with a shaft collar, retaining ring or grub screw. Once assembled, drive torque passes from the shaft into the side face of the key, then out through the mating face of the hub keyway, so the load is carried in shear and bearing rather than by clamping friction. Because the key is a discrete, replaceable part, it can also be specified to fail first and protect the more expensive shaft and gearbox behind it.

Take a belt conveyor drive on a packaging line. The gearbox output drives a keyed rotary shaft running in two pillow-block bearings, with a toothed drive pulley keyed to the centre of that shaft with shaft collars either side holding it on centre. Every time the line starts under a full load of product, the pulley sees a torque spike that would let a friction-only fit creep out of alignment and pull the belt off track. The key absorbs that spike and keeps the pulley indexed to the shaft, which is why the same arrangement turns up in robotic gantries, agricultural drivelines and pump and motor couplings.

Materials Keyed Shafts Are Made From

Accu's range of keyed shafts is machined from engineering-grade metals, each selected to balance torsional strength, corrosion resistance and rotating mass for a different class of application:

• Stainless Steel - (303): A free-machining austenitic stainless with solid general corrosion resistance, manufactured to ASTM A-582 Cond A.
• Stainless Steel - Marine (A4): Offers superior marine-grade corrosion and chemical resistance for washdown and coastal environments, manufactured to ASTM A-276 Cond A.
• Steel - (C45): A medium-carbon steel giving high tensile strength and durability at a competitive cost per shaft, manufactured to ASTM A108.
• Steel - (1144): A stress-relieved grade with exceptional yield strength and fatigue resistance, the hardest option in the range at Rockwell C22 to C25 and manufactured to ASTM A311.
• Aluminium - (Grade 2024-T4): Just over a third of the weight of the equivalent steel shaft, with a high strength-to-weight ratio that suits low-inertia and fast-reversing assemblies, manufactured to ASTM B211 2024-T4 and T351.

Whatever the base metal, every shaft in the range is supplied precision ground to a consistent surface finish and diameter tolerance, so hubs and bearings slide on cleanly without further preparation.

Sizes & Types of Keyed Shafts Available.

Accu's range of keyed shafts is available in both imperial and metric series, across a broad spread of diameters, lengths and keyway sizes to accommodate a range of demanding engineering needs:

• Outer Diameter (OD): 5/16" to 2-7/16" imperial, 8 mm to 50 mm metric.
• Length (L): 3" to 72" imperial, 300 mm to 1800 mm metric.
• Keyway Width (KW): 3/32" to 5/8" imperial, 2 mm to 14 mm metric.
• Keyway Depth (KH): 3/64" to 5/16" imperial, 1.2 mm to 5.5 mm metric.
• Manufacturing Standard: ANSI B17.1-1967 imperial, DIN 6885-1 metric.
• Outer Diameter (OD) Tolerance: ±0.0025", +0/-0.003" and +0/-0.0035" imperial, +0/-0.05 mm and +0/-0.076 mm metric.
• Length (L) Tolerance: ±0.062" imperial, ±1.6 mm metric.
• Straightness Tolerance: 0.012 in/ft imperial, 0.33/300mm metric.
• Hardness: Rockwell B40 to Rockwell C25.
• Tensile Strength: 30,000 psi to 108,000 psi.

Keyway dimensions are fixed against diameter by the governing standard, so each shaft arrives with the correct keyway for its size and no separate selection is needed. Material availability does narrow at the extremes of the range: aluminium is offered on imperial shafts up to 1", the 15/16" diameter is machined in Steel - (C45) only and the metric series is supplied in the four stainless and steel grades. You will also need matching parallel keys to complete the drive connection.

FAQ:

Q: What does "keyed shaft" mean?

A: A keyed shaft is a rotating shaft with a keyway, which is a rectangular groove machined lengthwise along its outer surface. The term describes the presence of that groove rather than any particular diameter or material. The keyway accepts a separate parallel key, which bridges the shaft and the hub of whatever is mounted on it, locking the two together so they rotate as one. You will sometimes see the same component listed as keyseated shafting or keyed rotary shaft.

Q: How much torque can a keyed shaft handle?

A: There is no single figure, because torque capacity is set by the assembly rather than the shaft on its own. Two limits usually govern it: shear across the key's cross section and bearing pressure on the contact faces of the shaft and hub keyways. Both scale with the width of the key and its engaged length and with the shear and compressive strength of the key and shaft materials, which is why a larger diameter shaft carries more torque through its correspondingly larger keyway. For any specific application, calculate against the weakest of the three elements, the key, the shaft keyway and the hub keyway, then apply a safety factor for shock or reversing loads.

Q: What is the purpose of a key on a shaft?

A: The key turns a slip fit into a positive drive. Without it, a gear or pulley pushed onto a plain shaft relies on friction, which loosens under vibration and slips as soon as torque spikes. The key sits in matching grooves in both parts and physically blocks relative rotation, so drive is transmitted through metal-to-metal contact rather than clamping force. It serves two secondary purposes as well: it sets the angular position of the component on the shaft, which matters wherever timing is critical and it acts as a deliberate weak point, shearing under overload to protect the shaft, gearbox and driven machinery.

Bespoke Keyed Shafts Manufacture.

High precision, bespoke manufacture of Keyed Shafts to customer specification. State of the art facilities specialising in both small batch prototyping and large scale manufacture.