or Not to Drill
by Walt Gorman
Q. I hear different theories about drilling. One tech tells me that he drills every break, whether it is a star, a bullseye, or a combination. Another tech told me he does not have a drill in his kit, and another says he drills only some stars. What is your advice?
A. Not all breaks need to be drilled, but some do. Thirty to forty percent of stars and combinations need to be drilled, and most bullseyes do not. A tech without a drill is likely to either pass on repairing some tight stars or do a poor job on them. Either way he loses money or, possibly, an account to a tech who can do them.
All long cracks must be anchor-ed by drilling the end and popping a bullseye.
Occasionally a pocket of air trapped in a bullseye or a partial bullseye must be drilled and filled.
To test whether or not a pit is open, put a drop of thin resin on the opening. If it seeps into the crack, you can probably skip drilling. Then, while holding your drill at a 45 degree angle and bracing it with both hands, mark the spot where you are going to drill. Drill straight down through the impact point. This prevents your bit from skittering across the windshield and marking it up.
Never drill all the way to the PVB interlayer. Drilling 1/16-inch or half way into the first layer of glass usually is enough. At this point, an experienced tech will pop a bullseye by giving his drill a little push. Do not practice this on a customer’s car! Instead, use a sewing machine needle and tap lightly with a small screwdriver handle.
Avoid overheating either the glass or the bit by drilling in short bursts of two seconds, then cooling for two seconds This is called “burping,” and it will avoid black scorch marks in the glass and help prevent the bit from breaking off in the hole. Retrieving a broken bit is a time consuming nuisance.
Move the drill bit around the inside of the pit to remove shattered glass and debris. Take care not to enlarge the pit.
If a large chip is missing from the impact point, under cutting it will prevent the resin from popping out. Your dentist does the same thing with a filling in your tooth.
Walt Gorman is the owner and founder of A-1 Windshield Doctor in Seekonk, Mass. He has 17 years experience in windshield repair and runs a training school for technicians. E-mail your questions to email@example.com.
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