pint4

Drilling and tapping in chrome advice

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I am mounting outside rear view mirrors on the windshield posts on my 37PCKrd 120 Convertible Coupe.  I have to drill and tap four small holes for mounting screws in the chrome.  What is the best way to do it to avoid causing damage to the chrome plating beyond the holes being drilled?

Thanks,

Bob

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After all this time you've probably gotten it worked out but here is my two-cents worth anyway.  As a journeyman prototype machinist (long out of the trade), drilling chrome is a very tough job at best.  As the plating is only on the surface, it will likely chip or flake at the edges of the holes leaving unprotected areas that will eventually cause corrosion to the base metal.  Best to strip it, drill and tap the holes, then replate.

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I had the problem - I took a fine Dremel bit and cleaned up the edge - and then retapped  (starting with a regular tap and finishing with a bottoming tap) - the purpose of cleaning up the edge was to prevent the tap from catching on the chrome and pealing.

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