GlossaryKind of term: Manufacturing termKeyway
What is a keyway?
A keyway is a slot in a shaft or hub that holds a key carrying torque between them; its size and tolerance usually follow a key standard.
Keyways come in pairs: the slot in the shaft and the matching slot in the hub, of a gear or pulley for example. With the common parallel key, the shaft keyway is closed at both ends or runs out at one end, and the hub keyway runs through its full length. Width, shaft depth and hub depth belong to the shaft diameter and usually follow a key standard. A Woodruff key sits in a half-round seat in the shaft.
What does the standard say about a keyway?
In Dutch and German shops DIN 6885-1 is common for parallel keys and their keyways, and DIN 6888 for Woodruff keys; ISO and other national equivalents exist. The width carries a tolerance class for the kind of joint: for a normal fit N9 in the shaft and JS9 in the hub, for a tight fit P9 in both, for a sliding fit H9 in the shaft and D10 in the hub. The drawing states which applies. Depth is often given as a dimension over the shaft or hub bore, such as d − t1 and d + t2.
How does a keyway work in practice?
In a shaft, a closed keyway is milled with a keyway end mill and a run-out keyway with a side-and-face cutter or a keyway end mill. On a lathe with live tooling this can happen in the same setup as the turning; otherwise it is a second setup on a mill. A hub keyway needs a different process: slotting, broaching, shaping with a keyway tool on the lathe or machining centre, or wire EDM, depending on what the shop has. A width at N9 or P9 is checked with a gauge or gauge blocks. A symmetry or position requirement to the shaft axis means aligning or probing the shaft accurately.
What is a keyway often confused with?
A keyway is not the key: the key is the loose steel block, often a bought-in part, and the keyway the slot it sits in. Nor is a keyway a spline: a spline has several teeth all round and needs a profile operation of its own, such as hobbing, shaping or broaching.
How do you see a keyway in Blake?
In Blake, milling and mill-turn sit in the estimate as separate machining lines, with the time labelled as an estimate. If a subcontractor cuts the hub keyway, that step is its own outsourced line from your own library; if the price is missing, the line stays open. More on estimating.
Frequently asked questions
What do N9 and JS9 mean on a keyway?
Width tolerance classes for a normal fit under DIN 6885-1: N9 in the shaft, JS9 in the hub. The key then sits more firmly in the shaft than in the hub. For a tight fit, P9 applies to both.
How do you cut a hub keyway without a slotting machine?
With a keyway tool stroked along the axis on a CNC lathe or machining centre, by broaching if you have the broach and a press, or by wire EDM. Without any of those, outsource the step and price it as its own line.