Installing a dash-mounted rear-view mirror

[jwinkler]

Just got my Finish Line rear-view mirror. It came with two wood screws (image attached). The screws look to be about 1/8" diameter (inside the ... uh ... blades? Not sure what to call the part that actually makes it a screw). Should I drill a pilot hole, and if so, is 1/8" the appropriate diameter?

I've got a great (if under-maintained by me) finish supplied by CR in '92, and I don't want to hurt it - will I run that risk either drilling the holes or inserting the screws?

Thanks,

JLW

[Janusz]

You will need a pilot hole or risk chipping the surface layer. Not sure if 1/8" hole is correct. If you have a hidden area, you could experiment or call Finish Line for advice.

I was able to get to the underside of my dash, so I drilled clearance holes and bonded a small 1/4" plate to the underside that is tapped. Then substituted stainless machine screws for the wood screws.

[slithering]

JLW,

I know they send wood screws with the mirror, but I used tapered machine screws with nylon sleeved locknuts. Less chance of them becoming loose due to vibration.

Chris

[CJ428CJ]

If those screws aren't stainless steel, throw them away and replace them. I drilled pilot holes and still managed to break one off in the fiberglass.

Chris

[Bruce Edwards]

JLW the drill size would be the shank size of the screw. So if you take a drill bit and hold it up the shank of the drill you would want one the same size or just a tad larger than the shank of the screw.
The shank is the part in the middle.

[G.R.]

Make sure they are stainless--easy way put a magnet on them if it sticks buy stainless---tape your dash before drilling, helps to keep the glass and paint from chipping--drill one size under the screw screwshank ie: 1/8th shank use a 3/16th bit or a 7/64th bit-----use a silicone (RTV works great)as a lubricant and glass sealer---DON'T use a power driver---thread it in by hand, if starts to bind(it will), back it out and re-lube, try again, the screw will usually begin cutting threads again---I always have extra S/S screws of the size I need on hand, if the screwdriver slips you'll screw up the head, if you force the screw you will more than likely pop the head off--after you have drilled the holes re-lube the screws then mount the mirror.

I've installed a lot of equipment on boats in the last 20 years and this method works. Have used it on my car also.


PS--the Screws sent w/ my Finishline mirror were S/S-- hasn't wiggled or come loose yet from vibration.

[Double Venom]

GR...
Well done fella!

JLW, if you have a drill box, or a local hardware store that sells drills. Use yours/ their drill index box. Find a hole that the screw will barely fit into, then go down two drill bit sizes and you have the perfect sized bit. (By the way Finish Line screws will work quite well.)

ALWAYS start a hole in a painted fiberglass body with a bit at least two sizes smaller than your final hole is to be. This will eliminate any chance of chipping!

Now, to keep a screw tight in fiberglass that "wont" vibrate out or simply work loose, put a couple of drops of Loctite on it before final installation. It will never work loose until you want it to!

DV...The above works great on boats too! Tonneau cover snaps, convertible top snaps, fender mirrors, etc... Yup--this works.

[Dan Stryffeler]

Whatever you do, make sure you do it before you install the windshield... I spent about 2 hours twidling a drill bit between my fingers drilling the holes (through 1/4" thick fiberglass!) because I couldn't get an electric drill either through the top or from underneath. Not the stupidest thing I've ever done... but it ranks pretty high on the list.

- Dan

[rdorman]

Good tips here! Another one that I find helps eleminate chipping is to run the bit backwards. Still drills right through the glass but won't flake up the gel coat.

Rick