I work the front counter for Gary Brawer and I hear some weird stuff. Besides the guitar playing I hear comments, questions and exclamations. One of my favorite topics occurs when techs talk tech to each other. I love this stuff. I have, over the years, marked repeatedly the phrase: “Forstner bit.” As in, “Where are the Forstner bits?” or “That looks like a job for a Forstner bit.”
“What is a Forstner bit?” I asked myself, figuring I should find out. My job here is to answer the phones, sell and order parts and schedule repairs for Gary and the others. I am not a tech. Those people work in the back.
A Forstner bit turns out to be a drill bit for holes that need a flat bottom. “So…someone would use a Forstner bit to drill a hole in the top of a solid guitar body for the insert holes that accept bridge studs?”, I said to the techs. “No,” they returned patiently, “for that you would use a brad point bit.” “Oh,” I thought, obviously unclear on the concept. I would need to do some deeper research.
This unique drill bit was invented in the 19th century by a Benjamin Forstner, an American gunsmith looking to make a smoother hole. He got rich off his invention, too, licensing the technology to Colt Firearms and other gun makers.
So how for a guitar would we use a Forstner bit? Well, it’s a perfect way to make deeper a cavity to accept, say, longer pickup flanges – the metal tabs that accept pickup height adjustment screws. When making a deeper hole it’s a concern to avoid going through the wood of the back of the body. So: a hole with a flat bottom. But there’s a center point in the bit, to guide its direction, so diligence is still required.
The Forstner bit has other beneficial features. Its shape is very stable at spin (compared to other bit shapes) and also resists something called “tear-out” a phrase indicating how clean a hole can be drilled. The bit is not commonly used in hand drills – it’s hard to push – a drill press is typical. Rickenbacker has been known to use Forstner bits to drill wiring channels, an observation that shocks some of the more fastidious technicians.
I learn something new at this job every day.