Machine Keys
Straight keys, with a square or rectangular cross section, are the most common type of key. Install them in keyways to transmit torque from shafts to gears and other components. Machine keys are often the same material as the shaft and other components with which they are used. To use a key as a sacrificial part, choose a softer key that will shear off when parts are exposed to excessive force, preventing damage to expensive equipment.
Steel keys are strong and easy to machine. Since steel is the most common material, these keys work in many applications. Steel keys rust when exposed to moisture, so they should only be used in dry environments. Zinc-plated steel keys resist corrosion in wet environments.
18-8 stainless steel keys offer a balance of strength and corrosion resistance. They may be mildly magnetic.
Slightly larger than the size listed in the table, oversized keys fit tightly in a keyway. Press them into place for use in high-torque applications or to replace a key in a worn keyway. Slightly smaller than the size listed in the table, undersized keys are the choice when you need a slightly looser fit or when you have an inconsistent keyway. Use them when parts need to be taken apart frequently, such as for maintenance or prototyping.
Keys that meet ANSI B17.1 specifications conform to ANSI standards for dimensions and tolerances.
For technical drawings and 3-D models, click on a part number.
Tolerance | ||||||||
|---|---|---|---|---|---|---|---|---|
| Lg. | Tolerance Rating | Ht. | Wd. | Minimum Hardness | Specifications Met | Pkg. Qty. | Pkg. | |
1008-1045 Carbon Steel | ||||||||
1/8" × 1/8" | ||||||||
| 1/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 000000 |
| 1/2" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 0000 |
| 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 3/4" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 00000 |
| 3/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 0000 |
| 1" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1 1/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 00000 |
3/16" × 3/16" | ||||||||
| 1/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B97 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1/2" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 0000 |
| 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 3/4" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 0000 |
| 3/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 7/8" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B97 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 0000 |
| 1" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1 1/8" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B97 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1 1/4" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 00000 |
| 1 1/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1 3/8" | Oversized | 0.000" to 0.001" | 0.000" to 0.001" | Not Rated | ANSI B17.1 Class 2 | 5 | 000000000 | 0000 |
| 1 3/8" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Not Rated | ANSI B17.1 Class 1 | 5 | 000000000 | 0000 |
| 1 1/2" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 0000 |
| 1 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1 3/4" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 00000 |
| 1 3/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 2" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 00000 |
| 2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 2 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 3" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B97 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B97 | ANSI B17.1 Class 1 | 10 | 000000000 | 00000 |
1/4" × 1/4" | ||||||||
| 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B97 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 3/4" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 0000 |
| 3/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 0000 |
| 1" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1 1/4" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 00000 |
| 1 1/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1 1/2" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 0000 |
| 1 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1 3/4" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 00000 |
| 1 3/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 2" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 00000 |
| 2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 2 1/4" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 00000 |
| 2 1/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 2 1/2" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 5 | 000000000 | 0000 |
| 2 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 3" | Oversized | 0.000" to 0.001" | 0.000" to 0.001" | Not Rated | ANSI B17.1 Class 2 | 5 | 000000000 | 0000 |
| 3" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 00000 |
| 3 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B97 | ANSI B17.1 Class 1 | 10 | 000000000 | 00000 |
| 4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B97 | ANSI B17.1 Class 1 | 5 | 000000000 | 0000 |
| 5" | Oversized | 0.000" to 0.001" | 0.000" to 0.001" | Not Rated | ANSI B17.1 Class 2 | 5 | 000000000 | 0000 |
| 5" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B97 | ANSI B17.1 Class 1 | 5 | 000000000 | 0000 |
5/16" × 5/16" | ||||||||
| 1 1/4" | Oversized | 0.000" to 0.001" | 0.000" to 0.001" | Not Rated | ANSI B17.1 Class 2 | 5 | 000000000 | 0000 |
| 1 1/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 00000 |
| 2 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 00000 |
3/8" × 3/8" | ||||||||
| 1" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 00000 |
| 1" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B97 | ANSI B17.1 Class 1 | 5 | 000000000 | 0000 |
| 1 1/4" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 5 | 000000000 | 00000 |
| 1 1/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 0000 |
| 1 1/2" | Oversized | 0.000" to 0.001" | 0.000" to 0.001" | Not Rated | ANSI B17.1 Class 2 | 5 | 000000000 | 0000 |
| 1 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 00000 |
| 1 3/4" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 00000 |
| 1 3/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B97 | ANSI B17.1 Class 1 | 5 | 000000000 | 0000 |
| 2" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 00000 |
| 2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 00000 |
| 2 1/4" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 10 | 000000000 | 00000 |
| 2 1/2" | Oversized | 0.000" to 0.001" | 0.000" to 0.001" | Not Rated | ANSI B17.1 Class 2 | 5 | 000000000 | 0000 |
| 2 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 10 | 000000000 | 00000 |
| 2 3/4" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 5 | 000000000 | 00000 |
| 2 3/4" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Not Rated | ANSI B17.1 Class 1 | 5 | 000000000 | 0000 |
1/2" × 1/2" | ||||||||
| 1" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 1 | 000000000 | 0000 |
| 1" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 1 | 000000000 | 0000 |
| 1 1/2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 5 | 000000000 | 00000 |
| 1 5/8" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 5 | 000000000 | 00000 |
| 1 5/8" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Not Rated | ANSI B17.1 Class 1 | 5 | 000000000 | 0000 |
| 2" | Oversized | 0.000" to 0.002" | 0.000" to 0.002" | Rockwell B50 | __ | 5 | 000000000 | 00000 |
| 2" | Undersized | -0.002" to 0.000" | -0.002" to 0.000" | Rockwell B50 | ANSI B17.1 Class 1 | 5 | 000000000 | 00000 |