What is a Serration shaft?

The term "Serration" for motor shafts, also commonly known as knurling, ribs, or ribs, refers to the regular or irregular raised ribs formed on the surface of a section of a motor shaft through stamping or rolling.

I. The Core Function of Motor Shaft Stamping

1️⃣ Preventing Part Slippage (The Primary Reason)

The motor shaft typically mates with the following parts:

Fan blades

Gears

Couplings

Pulleys

Copper sleeves / Plastic sleeves

2️⃣ Improved Reliability of Interference Fits

Many motor shafts and parts are:

Interference Fit (Pressure Fit)

The Role of Ribs:

The ribs are "compressed and deformed" during press fitting.

Automatically compensates for minor errors in bore diameter.

Less prone to loosening than plain shafts.

In actual production, for the same interference fit, ribbed shafts have 30%–100% higher torsional strength than plain shafts.

3️⃣ Reduced Processing Costs

To achieve the same effect without ribs, typically:

Stricter shaft tolerances

Higher precision hole machining

Even adding keyways or adhesives (such as anaerobic adhesives)

While ribs:

Simple and fast process

Low cost

No additional assembly steps required

4️⃣ Prevent loosening after long-term use

Motors experience the following during operation:

Vibration

Thermal expansion and contraction

Start-stop impact

Strike force:

Absorb minor assembly errors

Suppress fretting

Extend overall machine lifespan

II. Why use ribs instead of keyways?

Comparison:                                                          Ribs vs.                            Keyways

Machining Cost:                                                     Low vs.                            High

Machining Speed:                                                  Fast vs.                            Slow

Suitable for Small Shaft Diameters:                          ✅                                 ❌

Dynamic Balance Impact:                                      Small vs.                          Large

Mass Production:                                            Very Suitable vs.                 Unsuitable

III. Common Rib Forms

1️⃣ Straight Ribs (Longitudinal)

Best torsional resistance

Commonly used in gears and couplings

2️⃣ Diagonal Ribs / Diamond Ribs

Torsional resistance + axial force resistance

Commonly used in plastic fan blades

3️⃣ Local Ribs

Ribs only in the assembly section

Easy to position and disassemble

IV. When is Serration machining absolutely necessary?

✅ Ribbed machining is strongly recommended in the following situations:

Plastic parts directly pressed onto the shaft

Copper bushings / Powder metallurgy gears

Small shaft diameter, relatively high torque

No glue application allowed, no looseness allowed

❌ Ribbed machining is generally not recommended in the following situations:

High-speed precision shafts (extremely sensitive to concentricity)

Existing keyways or splines

Structures requiring frequent disassembly and assembly