Woodruff keys work well near shaft shoulders, where a standard open keyway would create too much stress. They are also often used on tapered shafts. These keys have a rounded shape that makes them easy to remove when parts need to be taken apart frequently, such as for maintenance or prototyping. Because they're usually shorter than standard machine keys, they work best in light duty applications. Use them to connect gears and other components to shafts. Also known as half moon keys.
Steel keys offer good strength.
316 stainless steel keys have excellent corrosion resistance, but aren't as strong as steel keys. They may be mildly magnetic.
Inch keys conform to ANSI B17.2 standards for dimensions and tolerances.
Metric keys conform to DIN 6888 standards.
| Normal size b | 1 | 1.5 | 2 | 2 | 2.5 | 3 | 3 | 4 | ||
| b | max=nominal size | 1 | 1.5 | 2 | 2 | 2.5 | 3 | 3 | 4 | |
| min | 0.975 | 1.475 | 1.975 | 1.975 | 2.475 | 2.975 | 2.975 | 3.97 | ||
| k | max=nominal size | 1.4 | 2.6 | 2.6 | 3.7 | 3.7 | 5 | 6.5 | 6.5 | |
| min | 1.34 | 2.54 | 2.54 | 3.625 | 3.625 | 4.925 | 6.41 | 6.41 | ||
| d1 | max=nominal size | 4 | 7 | 7 | 10 | 10 | 13 | 16 | 16 | |
| min | 3.88 | 6.85 | 6.85 | 9.85 | 9.85 | 12.82 | 15.82 | 15.82 | ||
| s | min | 0.16 | 0.16 | 0.16 | 0.16 | 0.16 | 0.16 | 0.16 | 0.25 | |
| max | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.4 | ||
| Normal size | 4 | 5 | 5 | 5 | 6 | 6 | 8 | 10 | ||
| b | max=nominal size | 4 | 5 | 5 | 5 | 6 | 6 | 8 | 10 | |
| min | 3.97 | 4.97 | 4.97 | 4.97 | 5.97 | 5.97 | 7.964 | 9.964 | ||
| k | max=nominal size | 7.5 | 6.5 | 7.5 | 9 | 9 | 10 | 11 | 13 | |
| min | 7.41 | 6.41 | 7.41 | 8.91 | 8.91 | 9.91 | 10.89 | 12.89 | ||
| d1 | max=nominal size | 19 | 16 | 19 | 22 | 22 | 25 | 28 | 32 | |
| min | 18.79 | 15.82 | 18.79 | 21.79 | 21.79 | 24.79 | 27.79 | 31.75 | ||
| s | min | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.25 | 0.4 | 0.4 | |
| max | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 | 0.6 | 0.6 | ||