A key transmits torque by sitting in the keyways between a shaft and a hub. The same cross-section comes in four end shapes; pick the wrong one and it will not fit the keyway — the difference is only at the ends, not in the cross-section.
| Name | End shape | Matching keyway | Typical use |
|---|---|---|---|
| Parallel key (square-end key) | Square corners at both ends | Straight slot open at both ends (planed or broached) | Long shafts, sliding fits, cut to length on site |
| Single-round-end key | One end round, one end square | Slot closed at one end (end-milled to the end) | Locating at a shaft end, butting against one side |
| Round-end key (double-round-end) | Round at both ends | Slot closed at both ends (end-milled) | The most common milled keyway |
| Woodruff key (half-moon key) | Semicircular (crescent) | Deep arc-shaped slot (cut with a keyseat cutter) | Tapered shafts, low torque, easy alignment |
Rule of thumb: first check whether the ends of the keyway are round or square, and pick a key with the same end shape. If unsure, send us a photo or drawing of the keyway with your inquiry.
Parallel and round-end keys are always written as width × height × length (mm); for example 10*10*100 means width 10, height 10, length 100. Inch keys are given in inches (e.g. 1/4 × 1/4 × 48). Woodruff keys are written as thickness × outer diameter × height. If a length does not suit you, keys can be cut or made to your drawing — just put the requirement in your inquiry.
| Item | Details |
|---|---|
| Common standards | JIS B 1301 (keys and keyways; CNS is derived from the same source), DIN 6885 (form A round end / form B square end / form C single round end); Woodruff keys correspond to DIN 6888 |
| Common materials | S45C medium carbon steel (main line, also heat-treated versions), 304 stainless steel (corrosion resistant), 316 stainless steel (better corrosion resistance) |
| Tolerance | Cross-section tolerance follows the standard grade; for individual items the product page takes precedence. If you need a specific grade, state it in your inquiry |
Click a size to open its product page (price and stock status); lists update automatically with our stock. Stainless parallel keys, inch sizes and special lengths are also in stock — search the interactive catalog.