by Bob Beranek
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The other day I asked the class I was teaching how they handled outside rearview mirror replacement. Most said they bought pre-cut mirrors, stuck them to the mounting plate in the mirror assembly and then taped it up until the adhesive cured. However, one installer said he used flat stock mirror and cut it to pattern. This really surprised me because I thought cutting mirror stock to pattern was a thing of the past.

I remember instructing my students how to pattern and cut stock mirror to fit mounting plates in the past, but I don’t typically teach that today. Sure, flat stock is slightly cheaper and cutting the part is a convenience to the customer because it can be done immediately rather than ordering and waiting for shipment, but please keep in mind it does not meet Federal Motor Vehicle Safety Standard 111 on the passenger side of the vehicle.

The mirror on the passenger side of the vehicle is required by law be convex and display the words, “Objects in Mirror Seem Closer than They Appear.” As a repair facility we cannot render a safety device inoperative. By changing an outside rearview mirror from convex to flat we are changing a safety device to be ineffective. The driver will not be able to see the blind spots on the passenger side of the vehicle. There is an exception for large, over-the-road, heavy haulers. The rule is that if the mirror has over 19 square inches in surface area, the mirror can be flat stock if the vehicle owner so requests but other than that exception the mirror must be convex.

However, for those of you who still cut mirror stock for the driver side of the vehicle here is the way I used to teach patterning for the part. I learned this from a manager friend named Ed Landerud. The hardest part of cutting the mirror stock to size was to get the pattern right. If it was cut too small, all the profit was lost to scrap stock. If it didn’t fit close to perfectly, the customer complained and a re-cut was in order. So here is how I did it.

1.            Get a white sheet of paper and hold it up to the mounting plate placing one finger in the center to hold it in place.

2.            I then took my other index finger and dragged it on the floor to collect dust or dirt. I used my finger to then outline the pattern on the paper using the edge of the mounting plate. It created an outline by which to estimate the shape and size of the pattern.

3.            I then cut the paper with scissors to create a template that I would use to trace the pattern to the flat stock mirror with a felt tip pen or wax pencil.

4.            The actual pattern would be slightly larger than the actual size due to the depression of the paper during the finger tracing of the plate.

5.            Once the pattern is cut, I would then finish the edging until it fit perfectly.

6.            Here is another word of advice. Some mirror stock will not perform as well as others when adhered to the mounting plate with urethane. Some mirror stock backing will separate from the glass when urethane is used to adhere it. I would suggest using silicone or epoxy when adhering the mirror to the mounting plate.

Obviously, the dirty finger method of pattern making may not be the most professional way of creating a pattern, but it worked well. Now, as then, we have to get the job done, please the customer and do it safely and according to standard and regulation.