Can You Drill Brake Rotor Out To 5/8 Which Is 40/64 Or Will That Be To Loose

I’m doing the Brennan metcalf disk brake conversion . The directions say to drill out the rotor wheel stud holes to 39/64 that is a odd ball drill bit size. Can you drill them out to 5/8 which is 40/64 or will that be to loose I’m just trying to not have to buy a expensive drill bit I’ll only use once.

 

The correct drill will have the studs ‘press’ fit (or you can drive them in) to the hub, preventing them from loosening or turning.

I bought the proper size from an internet vendor for around $10, I think. Since I worried about it breaking - not uncommon when enlarging a hole - I bought two. That way, the first will easily last until I’m dead, and my sons will have them.

I drilled out four hubs on the Willys wagon. The .615” knurled studs fit nicely.

5/8” is .016 too large; I wouldn’t use it. I have a 5/8 drill bit, but bought the correct size.

Jon B.

 

^ what he said. I used a stepped bit with the increment I needed so the smaller step was the centering pilot.

 

Saw this on his page


Brennan's Garage
I had a customer send back in an idea about an alternative wheel stud that provides for a no-drill rotor option. His notes where: For the wheel studs, i replaced them with the same ones that come on a Bantam trailer. The knurled part is shorter and only goes through the hub. I was able to install the rotors without needing to drill them out.
Wheel Studs part numbers:
Napa 641-1137
Dorman 610-191
Raybestos 0528B

 

I bought the bit. Minimal price to pay, and if you are a typical jeepers you may be doing it a few times on different vehicles.
My "one time use" has now drilled out 10 rotors doing the Metcalf conversion

 

I've never regretted buying any tool. Now, if I could only find the one I need...

 

There are a few tools that were junk that I wish I bought better. I don't like buying stuff if not needed. Typically I'll break the wrong tool or a cheap one and need to buy the right one and a replacement for the other later.

 

I would drill it too small and wallow it out till it fits good. Its not a critical thing anyway. Are you worried about balance? How fast do you plan on going. Its not like its going to hit the caliper being .008 out of true

 

I used a step bit from the back of the rotor just enough to seat the rotor completely no need to drill all the way through. the rotor is just a slip fit anyway.

 

This is also what I did.

 

Maybe I'm too picky but the consequences of too loose a fit there could result in more than a few difficulties getting lug nuts loose down the road when things get a little corroded and you manage to strip the hole. Buy the bit! You don't need anything high tech, just a plain old jobbers drill like this:
https://www.wttool.com/3964-118a-point-bright-finish-jobber-drills-x300a-rdx

That has also been my take. Maybe that was the result of watching my late father struggling through repairs with his make-do tools. From is 1/2 drive socket set, JC Whitney quality with all the common sizes broken, through just buying individual sockets for what he couldn't get done otherwise, a certified frustration experience. The only plus side was that most of those individual sockets he purchased are Wright and I have yet to break one of them.