Machining Keyseats and Keyways
Choose a shaft or hub cutting method, then check keyseat or keyway location, width, depth and fit.
A key joins the shaft slot to the hub slot to transmit torque
A key joins the shaft slot to the hub slot to transmit torque
Before choosing a cutting method, identify which part needs the recess: the keyseat in the shaft or the keyway in the hub. See Keys and Keyways in Shaft-Hub Connections for the joint's terminology, diagram and torque path.
Identify the key by its cross-section and seating shape
Identify the key by its cross-section and seating shape
Use the specified key form and drawing dimensions to choose the feature you need to make. Review key forms, fit and axial retention before planning the cut.
Mill a shaft keyseat with the cutter that matches its end and bottom shape
Mill a shaft keyseat with the cutter that matches its end and bottom shape
An end mill can make a straight, flat-bottom shaft keyseat that ends within the shaft's length. Its diameter leaves rounded ends in plan view; confirm that the key and drawing allow that shape. Use a permitted entry method for the selected cutter.
A Woodruff keyseat cutter is a disk-shaped cutter on a shank. Its diameter forms the curved recess for a Woodruff key and its cutting width establishes the slot width. Match both dimensions to the required recess. Not every tool sold as a keyseat cutter is the correct tool for every key.
- Read the keyseat's width, depth, length or cutter diameter, and axial location from the drawing.
- Support and secure the shaft against rotation and displacement. Use Milling Vises and Strap Clamps for the setup.
- Align the shaft axis with the intended machine travel and locate its centerline using Mill Indicators and Part Zero. Set the cutter's cutting plane or path on that centerline, with the specified axial location and depth reference.
- Choose the tool and entry method with End Mill Anatomy and Cutter Selection and plan the cut with Milling Operations. Cut to the planned allowance, measure, then finish to the required dimensions.
Review Equipment Operating Procedure and mill hazards in the safety collection before operation.
Why cutter selection includes more than width
Reach, neck clearance and tooth arrangement affect access and cutting behavior. See Harvey Performance's keyseat cutter considerations. A nominal tool width does not certify the width of the finished slot.
Broach a through hub keyway; consider slotting when the geometry needs it; Practice
Broach a through hub keyway; consider slotting when the geometry needs it
A conventional keyway broach and guide bushing are useful for a straight keyway through a hub bore. See Broaching for the pass sequence. The same arrangement does not make a closed-end keyseat on the outside of a shaft.
Shaping or slotting uses a reciprocating single-point tool to remove material in successive strokes. A suitable internal slotting setup can make a hub keyway when a through broach is unsuitable. Blind work still needs a planned tool runout and chip space; the method must fit the actual geometry.
Check width, depth and location before using assembly as a fit check; Checklist
Check width, depth and location before using assembly as a fit check
- Clean the feature and remove burrs without rounding the functional edges.
- Check width at several accessible positions using a suitable slot gauge, gauge blocks or measuring contacts. Select a tool with enough access and resolution for the tolerance; see Choosing Shop Measuring Tools.
- Measure depth from the drawing's stated reference. A depth instrument needs a stable reference bridge or fixture on a round shaft; resting it arbitrarily on the curved surface changes the result.
- For a hub, establish the specified bore-to-keyway measurement with an appropriate internal/keyway gauge or fixture. A reading across the bore and slot includes the bore dimension; it is not automatically the radial slot depth.
- Check length, axial position and centerline location. Compare actual measurements with the drawing limits.
- Check the specified key fit and assembly clearance. Investigate interference or unwanted movement instead of forcing the assembly together.
A key that enters the slot is a useful functional check, but it does not prove depth, location or dimensional compliance.