Hard Chrome Plating Tolerance
Q. We have a drawing calling out for a deposit of 0.004 with a tolerance of + 0.0011/- 0.000, our local plating company tells us that the part will have to be ground down after plating to hold these tolerances. Do I believe them or look around? Thanks for any assistance.
A. Tom, If the 0.004 + 0.0011/ - 0.000 is per-side, the plater is correct. For best results chrome should be over-plated 0.001 to 0.003 per side and subsequently ground to final finish.
Chrome plating to a successful final dimension without subsequent grinding, requires additional involvement by plating personnel as well as specialized tooling and skills. A willing plating shop may have to build or buy conforming anodes as apposed to using stick anodes. Several factors must be considered before deciding.
1.) Is the 0.004 total chrome on diameter, meaning 0.002 per side, adding up to 0.004? or is the call out for 0.004 minimum thick, or 0.004 to 0.0051 thick?
2.) Is the before plating diameter close to or at finish size now? Or undersize. If so? How much below finish size?
3.) Is there an after chrome plating minimum micro finish called out on the drawing?