DIN 6888 Woodruff Keys
Woodruff keys are semicircular - a segment of a disc that sits in a matching pocket milled into the shaft, with its flat top standing into the hub keyway. The deep, curved seat lets the key rock slightly to align itself with the hub, which suits tapered shaft ends. We supply them in key steel, available across metric sizes from 2 × 10mm to 10 × 45mm with inch sizes alongside.
Also known as: woodruff key, half moon key, semicircular key, bs 46 woodruff, bs 4235 woodruff, din 6888.
DIN 6888 (BS 4235 Pt 2) dimensions
| Key size (t × h × d) | Shaft diameter, torque drives | Shaft diameter, location duty |
|---|---|---|
| 1.0 × 1.4 × 4.0mm | over 3 to 4mm | over 3 to 4mm |
| 1.5 × 2.6 × 7.0mm | over 4 to 5mm | over 4 to 6mm |
| 2.0 × 2.6 × 7.0mm | over 5 to 6mm | over 6 to 8mm |
| 2.0 × 3.7 × 10.0mm | over 6 to 7mm | over 8 to 10mm |
| 2.5 × 3.7 × 10.0mm | over 7 to 8mm | over 10 to 12mm |
| 3.0 × 5.0 × 13.0mm | over 8 to 10mm | over 12 to 15mm |
| 3.0 × 6.5 × 16.0mm | over 10 to 12mm | over 15 to 18mm |
| 4.0 × 6.5 × 16.0mm | over 12 to 14mm | over 18 to 20mm |
| 4.0 × 7.5 × 19.0mm | over 14 to 16mm | over 20 to 22mm |
| 5.0 × 6.5 × 16.0mm | over 16 to 18mm | over 22 to 25mm |
| 5.0 × 7.5 × 19.0mm | over 18 to 20mm | over 25 to 28mm |
| 5.0 × 9.0 × 22.0mm | over 20 to 22mm | over 28 to 32mm |
| 6.0 × 9.0 × 22.0mm | over 22 to 25mm | over 32 to 36mm |
| 6.0 × 10.0 × 25.0mm | over 25 to 28mm | over 36 to 40mm |
| 8.0 × 11.0 × 28.0mm | over 28 to 32mm | over 40mm |
| 10.0 × 13.0 × 32mm | over 32 to 38mm | — |
Materials & strength
Self-aligning seat
The key can tilt in its curved pocket to line up with the hub keyway, taking up small angular differences - the reason the pattern is standard on tapered shaft ends.
Mainly light duty
The deep pocket removes more shaft section than a parallel keyway, so the pattern is chiefly a light-duty drive and locating key rather than a heavy transmission element.
Sized by thickness, depth and diameter
A Woodruff key is specified by its thickness, depth and nominal disc diameter - the table on this page relates each size to the shaft diameters it serves for drive and for location duties.
Related specificationsHow do I choose a Woodruff key size?
Work from the shaft diameter and the duty. The selection table gives one size band for torque-transmitting drives and a second for purely locating duties, which run one or two sizes smaller for the same shaft.
What are Woodruff cutter numbers?
DIN 6888 Woodruff keys are identified by their nominal width × diameter dimensions. The key number in the DIN system is a sequential reference, not an encoding of shaft or cutter dimensions — specify by width and diameter when ordering.
Woodruff or parallel key?
Parallel keys carry heavier drives and preserve more shaft section; Woodruff keys win where self-alignment, a tapered seat or a short hub makes the semicircular form more practical.
Need DIN 6888 (BS 4235 Pt 2) in a non-standard size or material?
Send us your drawing — specials quoted within 24 hours.