Hard chrome plating is often associated with the production of new shafts but in reality worn shafts can be repaired back to original dimensions using chrome plating. The key is to approach the job methodically from the start.
Assessing Whether the Shaft Is a Candidate
Cracks, deep scoring or pitting covering more than approximately 20% of the surface area of the shaft are typically not repairable by plating. Even shallow wear of a uniform nature is typically an ideal candidate for plating. Corrosion or wear that is severe enough to expose the base material of the chrome and create additional surface area would not typically be repairable by plating.
Measuring Wear and Specifying Deposit Thickness
To establish whether your shafts can be chrome plated, it is necessary to measure the wear on the shafts. Typically this is done by measuring the worn diameter of the shafts over a number of positions on the bearing journal. From these measurements it is possible to calculate the total material loss from the original nominal size of the shafts.
Surface Preparation Before Plating
This cleaned shaft will then be dressed back to good material and all stress raisers such as sharp shoulders or tool marks will be blended out. The completed shaft will then be despatched to the plater.
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Post-Plate Grinding to Final Tolerance
A Chrome plated shaft will typically be supplied with the deposited material raised in the form of a peak. This material is then ground to the required tolerance, e.g. h6 or h7, for bearing applications. The finished dimensions of the plated shaft can be held to within 0.01 mm using suitable cylindrical grinding.
When the Shaft Is Too Far Gone
Hard chrome plating has limitations. If the shaft’s base metal is cracked, severely pitted, or worn beyond the shaft’s ability to be machined back to its original dimensions, the best option is to consider a thermal spray rebuild or completely replace the shaft. Early failure of the plating could result in damage to surrounding housing.
So there’s a little upfront work but in the end it saves you time and money.
