“MACHINING” BRAKE DRUMS FOR LARGER WHEEL STUDS
Most aftermarket axles are drilled for wheel studs with a minimum diameter of ½ inch. That can be an issue if you have a GM small or intermediate car. They were factory fitted with 7/16-inch studs. That means the brake drums won’t slide over the bigger studs. Drilling out the hole with a standard ½-inch drill bit won’t work. If you’ve ever tried to enlarge holes one size over with a regular drill bit, you know what happens next: You end up with an oval-shaped hole. The solution is a step drill.
Step drill bits are nothing new, but honestly, quality is all over the map. We didn’t have one we could trust, so we spent an hour or two checking them out. Believe it or not, Home Depot had what we were looking for. On a tip from a retired electrician, we bought a USA-made Klein step drill bit. They are quite a bit more money than most of the others, but wow! You can knock out the stud holes in the drums in less than a minute (honestly). Equally important, there’s quite a bit of distance between the steps on the drill bit. That gives you accurate control when you’re drilling one or two sizes over.
The solution is to use a high-quality step drill to enlarge the hole. This one is manufactured by a company called Klein, and we purchased it at Home Depot.
After redrilling, the brake drum slides right over the larger studs. Good tools make this job simple, and you don’t have to take the parts to a machine shop.
On a day-two car with aftermarket axles, you’ll find that wheel stud diameters start at ½ inch. That means a Chevy small car brake drum (which is machined for 7/16-inch studs) won’t fit. Simply redrilling with a ½-inch bit won’t work because it will oval the hole.