Drilling and Tapping Holes in Chrome Plating

[pint4]

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

[JFranklin]

I would replace original mirrors in the original location and not mar a good piece of chrome.

[pint4]

Car never had mirrors.  These are correct for the year.  Cannot drive the car without them.  Zero rear visibility in a convertible and folks drive fast on the highways.

[JFranklin]

W

6 minutes ago, pint4 said:

Car never had mirrors.  These are correct for the year.  Cannot drive the car without them.  Zero rear visibility in a convertible and folks drive fast on the highways.

I would never have believed a 1937 car of any make would be delivered without mirrors. My mistake. I have found that drilling into nice material can be aided with the application of masking tape on the surface to be drilled, but not sure of chrome. someone will have a good answer I bet.

[JACK M]

Chrome or stainless.

If its a stainless part on the windshield posts screws may not hold very well.

If in fact the posts are chrome plated you may have better luck.

[Frank DuVal]

Outside rear view mirrors not required by federal law until the 1966 model year. Back in the cay I saw a lot of Chevrolet Biscaynes/Bel Airs, Fury 1s and Ford Customs  delivered without outside rear view mirrors, and then the owners might later be seen at Pep Boys.

 

I added an outside mirror  (driver's door) to my 1962 Biscayne when I bought it in 1973.

 

Also the same year backup lights became required by federal law. And the year all GM 3 speeds were synchroed in first, but that was a GM decision, not federal law! ?

[jrbartlett]

There are some mirrors that attach to the door hinges, if the hinges are exposed and on the front edge of the door (not suicide doors).

[jan arnett (2)]

I would use a dremel tool with a small cutter head to break the chrome first.  A diamond cutter would work well and not move around.

 

[Spinneyhill]

I would suggest a little zinc paint on the cut threads afterwards. A couple of layers at least. Make sure there are no oily residues on it first. When specifying corrugated steel pipes we always specified at least 2 coats of cold galvanising paint for repairs. You could even use a tiny rubber o-ring around the screws to keep water out, like the ones that come on Tek screws. The chrome will likely be damaged first by rust of the exposed steel.

[edinmass]

Simple answer, you NEVER drill through Chrome. NEVER. That being said, go to Amazon and buy a few suction cup mirrors for 8 bucks each. They work great, and come on and off easy. I run them on many, many great cars, no problem. Ed

[54vicky]

I drilled through my chrome plated a posts both sides years ago no rust? but then it is cast I added remote mirror on driver side factory option spotlight with mirror passenger side also factory the key is to use a good center punch then a good pilot bit the tip about masking tape is almost a must keeps punch from moving and leave on for drilling same reason.as with any tedious job slow and easy tapping oil will aide in the tapping then I would use anti-seize to ease future removal.as they will be dissimilar metals.do not use a lot of pressure when drilling or I and everyone in hearing will know when bit breaks.it will be tricky if no guide but use bracket as guide drilling a small pilot bit will allow you to drill again in proper spot hopefully you won't need second as screws are probably something like 1/8 or 3/16 area tap then re tap before trying screws in case of burrs like old saying measure twice drill once you will probably need help in locating where to mount if so double check their marks if not happy remove tape and try again if not remember there is no going back once you drill that first hole.get a good night sleep and no intoxicants??

[PFitz]

It's not difficult to drill a chrome plated surface. Yes, a drill bit won't bit into the chrome. and  punching and drilling risks pulling up the edge of the plating  that can start to delaminate it and allow corrosion to eat under the edges. 

 

Mark the holes with a sharpie pen. Then, carefully using a pointed stone in a Dremel grinding tool, grind off the chrome  and nickel layers to expose the copper layer where the holes are to be drilled. Then just drill and tap as you would bare metal. By grinding off the hard brittle plating the drill bit can bite into the surface. Plus, by leaving the soft copper layer the plating wont start lifting like a cut edge through chrome., nor will corrosion start under the edge of the hole. 

 

Paul 

Edited September 10, 2018 by PFitz (see edit history)