“MA­CHIN­ING” BRAKE DRUMS FOR LARGER WHEEL STUDS

Muscle Car Review - - Tech -

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.

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