BOX 232 • MINNEAPOLIS, KS • 67467 HUYETT.COM • 785-392-3017 [email protected] • FAX 785-392-2845 MACHINE KEY FEATURES Machine keys are removable machine elements installed between shaft key seats and hub key ways The terms Shaft to transmit torque in power transmission assemblies. They can be machined; finished in a variety of Keys and Machine shapes, sizes, and materials; and tumbled by the thousands for automated assembly lines or just about Keys are used any application. Though simple in design, they are a necessity in the transfer of power. interchangeably To describe the same thing Design Considerations FORM FIT FUNCTION Machine Keys are An efficient undersize keys fit loosely, Machine ke ys may shear under solution for applications others fit snuggly, and oversize stress to protect people and requiring the transmission of keys can be filed to fit expensive equipmen t torque in an assembly See Page 8 for more de tails EASE OF USE LOCATION CORNER DESIGNS Tabbed and tapered Gib head Depending on the application, Key Sharp, square corners provide keys secure pulleys and gears ways are located at the end or the most surface con tact while tightly while allowing for quick along the length of the shaft radiused or chamfered corners removal during disassembly are a little easier to install and location can impact key design fully seat in a key way Keys for every application Top fitting gib head Parallel keys located in key Key ways located along Woodruff Keys are frequently keys ease assembly ways at the end of a shaft the length of a shaft allow used with tapered shafts. and disassembly. may protrude for full contact for full contact in assembly Although more difficult to between key and shaft. with no way for the key to install, they can not fall out work itself out. of an assembly. Prices, materials, dimensions, tolerances, designs, and grades subject to change without notice. © 2016 G.L. Huyett 48 HUYETT.COM • 785-392-3017 MACHINE KEY TYPES Form B Form A Gib Head Form B machine keys with both ends square More common in Europe than the U.S., Gib head keys are tapered machine keys feature straight, 90º parallel sides and form A machine keys have rounded end that are hammered in place to secure provide the most surface contact with both profiles so the key fully fills a milled key pulleys and gears tightly on the shaft. the key seat and the hub of a sprocket, way. Some users suggest that the round The added feature of a head provides for gear, pulley, or cog. design eases installation into the key way. easy removal. Page 56 Page 56 Page 70 Woodruff Hi-Pro Woodruff keys are used to avoid milling a A variation of the woodruff key is the high- key way near stress concentration prone profile or hi-pro key. These keys have “feet” shaft shoulders at the end of a shaft. With a that prevent the key from rocking and limit woodruff key, the key way does not extend movement in a rounded key way. Broad Selection to the end of the shaft so a stronger design is realized. Convenient, Easy Ordering 24/7 Manage Your Account Online Complete Order History Page 78 Page 84 Also Available... Oversize or Undersize? OVERSIZE UNDERSIZE The actual size of oversize The actual size of undersize material will be at least material will be at least the the specified size and may specified size and may be be slightly larger than the slightly smaller than the specified size within the specified size within the acceptable tolerance range. acceptable tolerance range. Hex and round Machine keys are available as a special order see pages 40 – 45 for Hex and round Key stock Prices, materials, dimensions, tolerances, designs, and grades subject to change without notice. © 2016 G.L. Huyett 49 BOX 232 • MINNEAPOLIS, KS • 67467 HUYETT.COM • 785-392-3017 [email protected] • FAX 785-392-2845 The terms Key Way and key DESIGN & USE seat are used interchangeably To describe the Machine Key Forms & MILLING KEY WAYS same thing Form B End mill enters End mill proceeds axially surface area of down the shaft surface Shaft creating a radiused end Upon exit, the end mill forms Form A another radiused end The profile of machine keys affect installation, bearing stresses, Because key ways are milled into the side of shafts using a and wear. While parts with square ends are more difficult to rotating cutter, the entry and exit points of the cutter into the install, round-end keys yield a greater coefficient of friction shaft form a radius or slot. Form A keys match the pattern of the with the key way, which reduces bearing stresses. key way which eases installation. Types of key ways SECONDARY PROCESS: HEAT TREATING OUR STANDARD MATERIALS POSSESS A TYPICAL HARDNESS OF HRB-80 PROFILE OR CLOSED Milled Along length of the shaft, but does not extend to end of the shaft HRB-80 SLED RUNNER NEED SOMETHING HARDER Look like the runners of a sled with a round taper on one end THAN HRB-80? CONTACT [email protected] or call 785-392-3017 For best results, enlist the help of a reliable WOODRUFF OR HI-PRO design engineer When Is cut along the length of the shaft with an designing new applications arbor cutting tool Prices, materials, dimensions, tolerances, designs, and grades subject to change without notice. © 2016 G.L. Huyett 50 HUYETT.COM • 785-392-3017 DESIGN & USE Cutting corners Square key way with Radiused key way with Radiused key way with square key stock square key stock radiused key stock Key ways may have filleted (rounded) corners to decrease stress concentration Key stock with square corners will not fully seat in filleted key ways Hold on Loosely Interference Fit Over-radiused machine keys with “rolled” corners fit A tight, interference fit, is produced when the machine looser in a key way and can lead to “rattling.” key is slightly larger than the key way it is installed in. See page 8 for more details. Shear Analysis Fretting Shear Plane Force A machine key may wear out or get distorted from high pressure and/or constant load bearing. Catastrophic Failure Torque Keys may fail if they are crushed due to excessive compression, bearing forces, or shear off in catastrophic failure. Keys can also wear out or get distorted through fretting If an application fails a machine key may shear or be from high pressure and constant load. crushed on load and will need to be replaced. Prices, materials, dimensions, tolerances, designs, and grades subject to change without notice. © 2016 G.L. Huyett 51 BOX 232 • MINNEAPOLIS, KS • 67467 HUYETT.COM • 785-392-3017 [email protected] • FAX 785-392-2845 SELECTING THE RIGHT KEY A number of considerations contribute to machine key design. Some designs are based on how the parts are used, while others look at how the parts are manufactured or enhance efficiency in assembly. For best results, consult with a design engineer when developing a new application. Parallel keys Gib head keys SQUARES AND RECTANGLES Square and rectangle profiles are the most common forms for Gib head keys are designed for applications that require periodic parallel keys. They are often referred to as straight keys. maintenance or removal during disassembly. Parallel or straight keys are more common in the U.S. and cost Typically the height is less than width. Gib head keys fit in the key less to produce than feathered keys. They are “side fitting” way with “top and side fitting” which bears load on all sides. which means they fit edge to edge in the key way. FEATHERED Rise Run Tapers are expressed in terms of rise over run. In other words, the amount of taper is stated per linear units of measure. A 1/8" taper per foot means that for every 12" in linear distance (run) the thickness of the part (rise) decreases by 0.125". Metric taper is 1:100. Feathered keys are parallel keys with round ends. They are more common in Europe. The round end design allows for the key to fully seat in the key way. Oversize or Undersize? OVERSIZE UNDERSIZE The actual size of oversize The actual size of undersize material will be at least material will be at least the the specified size and may specified size and may be in order to be slightly larger than the slightly smaller than the remove a gib specified size within the specified size within the head key with an extraction tool, A acceptable tolerance range. acceptable tolerance range. gap must be left between the head and the assembly Both the gib key and the Hub key way are tapered Prices, materials, dimensions, tolerances, designs, and grades subject to change without notice. © 2016 G.L. Huyett 52 HUYETT.COM • 785-392-3017 SELECTING THE RIGHT KEY Woodruff keys HI-PRO keys Woodruff keys, sometimes referred to as “half-moon” keys Hi-pro keys perform like woodruff keys, but have the added because of their shape, are designed to install and pivot in the benefit of “feet” that aid in installation by eliminating the key way and will not fall out once assembled. potential for the key to rock in the key way. Allows for increased strength Near the end of the shaft W.N. WOODRUFF Also Available... Woodruff keys were invented by W.N. Woodruff of Connecticut in 1888. The main purpose of the woodruff key is to avoid milling a key way near the stress concentrated end of a shaft.