Finish Thickness and Pre-Machining Allowance Calculator

A finish is a dimensional input before it is a cosmetic one. Pick the process and the thickness and this returns what the coating does to the dimension and how much to take off before the part leaves for the finishing line.

Thickness bands are the ones published in the finishing table on the CNC machining materials guide: MIL-A-8625 for anodizing, ASTM B633 for zinc plating and ASTM B733 for electroless nickel.

Choose the Finish

Calculate Allowance

Results

Why anodizing and plating behave differently

Anodizing converts the substrate rather than adding to it, so the dimension grows by half the coating thickness on each coated surface — a 50 µm hardcoat puts 25 µm on each face. Electroplated and electroless deposits are additive, so this tool treats their full thickness as growth on each coated surface.

Where the standards give minimums, not targets

ASTM B633 and ASTM B733 state a minimum thickness for each service condition or class, so the plater works to that floor and upwards. Name the service condition on the drawing rather than a thickness, and let the plater hold the minimum that condition carries.

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