Electric Motors & EV · Application
Press-fit knurling on motor and pump shafts
A straight knurl on the shaft locks rotor cores, commutators, impellers and couplings in place without keys, adhesives or splines.
- What was needed
- Straight Form Knurling Wheel, CNC Single Form Knurling Tool Holder, Lathe Single Form Knurling Tool Holder
- Requirements
- Torque transmission without keys or adhesives
- Repeatable press-fit interference
- Short, controlled diameter growth
- Industries
- Electric Motors & EVAutomotive & Auto ComponentsPumps, Valves & Flow ControlIndustrial Machinery & Gearboxes
- Result
- Hubs, cores and impellers stay locked on the shaft with fewer machining and assembly steps.
Problem
Rotor cores, commutators, fans, impellers and couplings must stay fixed on their shafts under starting torque, vibration and heat, for the whole life of the motor or pump. Keyways weaken the shaft and add machining steps; adhesives need curing time and are sensitive to temperature; a plain interference fit needs very tight tolerances on both parts.
Solution
A straight knurl (profile AA), form-rolled on the shaft where the hub sits, raises axial ridges a few hundredths of a millimetre above the original diameter. When the part is pressed on, the ridges bite into the smooth bore and create a combined form and friction fit that carries torque.
- Use form knurling: it displaces material, so the diameter grows in a controlled, repeatable way.
- Plunge knurling with a single-wheel holder suits short seats; feed knurling covers longer lengths.
- Choose the pitch with the shaft diameter and hub material; finer pitches for small shafts and laminated cores.
- Run a trial on the actual shaft material to set the finished diameter for the press fit.
Benefits
Why it works
No keyway or adhesive
Fewer machining steps and no curing time on the assembly line.
High torque in a short length
The axial ridges resist rotation directly.
Repeatable fit
Form knurling gives a predictable diameter growth batch after batch.
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