MECHANICAL FINISHING

If workpieces are hard chrome plated with thick layers (from 0.1 to 1 mm), final rectification is required to attain the specified tolerance. General guidelines recommend that a hard material (chrome) should be rectified with soft grinders as excess hardness may result in insufficient binding of the layer with the part.

It should be noted that reheating particular regions of a chrome-plated part during rectification may lead to the formation of cracks, thereby disrupting the homogeneity of the coating. Generally speaking, grinders with a hardness of J, K, L or M (soft to semi-hard, with average granulations of between 80 and 120 according to standard measures) are suitable for rectifying chrome coatings.

The grinder speed also affects the subsequent quality of the chrome and for each case depends on the shape, size and nature of the material which the part being rectified is composed of.

Rectification must always be performed with abundant cooling and passes of no more than 0.01 mm. As an example, guidelines for rectifying hard chrome coatings are provided below (Estarta and Ecenarro).

External cylindrical rectification Type of ginder
Up to ø 350 15A  120J 7V 19A 100HaJ 5V
From ø 350 to ø 450 15A  100J 7V 19A  80 Ha  5V
From ø 450 to ø 600 15A  80J 7V 19A 60HaJ

 9001        9100        IAQG