Roller Shaft

Function

The shaft transfers radial drum loads (and axial loads on thrust shafts) from the roller into the bearing housings and from there into the support frame. Shaft fatigue failure or severe journal wear causes sudden loss of drum support or roller seizure, resulting in unplanned shutdown and potential structural damage to the riding ring or drum shell. Correct material grade and surface hardness on the journals are essential for achieving the expected service life in this high-load, continuous-duty environment.

Construction & quality

Material: medium-carbon alloy steel to EN 19 (40Cr4) or AISI 4140 specification. Blanks are rough-turned, stress-relieved, and finish-ground on a CNC cylindrical grinder. Journal diameters are ground to k5/m5 tolerance for the correct interference or transition bearing fit. The keyway is milled to JS9 tolerance. Shaft straightness is held to ≤0.02 mm over full length. Journal surface hardness is 45–50 HRC by induction hardening; the core remains ductile to absorb shock. Centre holes are retained for re-inspection or re-grinding in the field if required.

When to replace

• Visible journal surface scoring, fretting marks, or rust banding visible when the bearing is removed
• Measurable undersize greater than 0.05 mm on journal diameter due to wear or corrosion
• Keyway showing signs of rolling or deformation at the key corner, indicating overload
• Drum oscillation or bearing noise attributable to shaft deflection under load
• Bearing inner race spinning freely on the journal, indicating loss of interference fit