Anyone tried to turn a brake rotor on their Granite? (2024)

jay.bolyard

Yes - I can take mine to the local autoparts store and get it done inexpensively with a machine specifically designed for it... but what fun would that be?

Curious if anyone has already tried it and how you did so to keep front/back surfaces parallel to each other and to the inner hub mounting surface simultaneously.

The diameter is such that the table cannot be under the rotor... maybe too much of a challenge?

Jay B.

Todd Tibbs

I did mine on a Midas 1220 with the smithy faceplate, although it did take all day to do four rotors and I made a error and had to redo one. Here is what I did: I made some equal length spacer that fit up where the lug/stud area of the hub fit up in the back and surfaced the front of the center opposite it to make sure it was all square, then flipped the rotor around and used faceplate studs with conical nuts(no spacers now) to attach. figuring this was square---runout seemed reasonable. I then made the cut on the inside of the rotor (inside of car/caliper) and squared this surface to the mounting pattern. Then simply flipped the rotor around and let the face I had kust cut rest on the faceplate and retain with same studs and cut the outside surface. Worked great, about to do the other car when spring comes. Just remember...if it seems to far out when you take your "trace" cut....double check your setup! Let me know if my instructions are too complicated...racing off to work....and what you save at the parts store will pay for your smithy faceplate!!! Todd

nedtron

Greetings Jay,

I have turned many large diameter work pieces on the Smithy Granite including custom steel fly wheels:

http://www.home-machine-shop.com/projects/Alum_Disks/

http://www.home-machine-shop.com/Custom_Fly_Wheel.jpg

However, turning the brake rotors for my Dodge Caravan wasn't really successful.

The brake rotors were mounted via a bolt pattern and centering boss on a steel 5C fixture and the circumference run out was acceptable.

The brake rotors were turned using carbide insert tooling and there was difficulty getting the finefinish thatI wanted.

After turning both sides of the rotors, the rotor thickness variations measured with a professional digital brake rotor micrometer exceeded ±0.001" which was considered unacceptable by the automotive machine shop owner who was tolerating and humoring my brake rotor machining experimentation.

There also appeared to be flatness and parallelism issues, however, the machine shop owner said "Give them a try and if you don't like it, we'll do them right!"

So I test drove the rotors on the Dodge Caravan and the brakes stopped well but there was a very low volumeunusual noise and the ABS equipped brake pedal didn't feel right.

So I took the brake rotors to the automotive machine shop and had them "do them right!" which resulted in no noise and the right brake pedal feel!

When I described the very low volume noise to the shop owner, he said that it was good that I had his shop turn the rotors because that noise would have only gotten louder with time and resulted in premature wear of the rotors and the pads.

The shop owner thought the rotor thickness variations, flatness and parallelism were the unacceptable issues with my home shop machined rotors.

Here is a paragraph from an article on brake rotors:

"FLATNESS & PARALLELISM
Opinions differ as to how much variation is OK in flatness and parallelism between the rotor faces. Some say as little as .0003 inch variation can cause a noticeable pedal pulsation on some vehicles.

The bottom line here is if the driver can't feel a pedal pulsation, the rotors are probably OK. But if there is a pulsation, you can usually assume the rotor is warped or has variations in thickness and needs to be resurfaced or replaced.

Measuring flatness and parallelism is difficult (some say impossible) because it requires numerous measurements all the way around the rotor (eight to 12 places at least). If the tip of the micrometer happens to line up with a small pit in the surface, it will give a false reading that may lead you to think the rotor is warped when in fact is isn't. Most technicians don't have the time to take all of these measurements, so they just turn the rotors, cross their fingers and hope the rotors are true. Usually they are."

Here is the complete article:

http://www.aa1car.com/library/2003/bf110322.htm

Ned

jay.bolyard

Well - between Ned and the other Jay...

I guess I'm clear to not bother... Thanks for sharing your experience and stopping me from wasting my time.

Jay B.

hotlumpy

Jay and Ned are definitely very skilled and respected by me and others, But I will have to repectfully dis-agree that it can't be done adequately on a Smithy. It definitely isnt a fast process though.

I did use a wrap of latex tube on the OD for noise reduction. The ones I did have been working fine for about 20,000 miles. I won't be afraid to do my other vehicle myself when it needs it, even though I have axcess to a brake lathe. I have turned hundreds of pairs of rotors on commercial AMMCO brake lathes in many shops I have worked in...and although easier to set up, faster, and do have the ability to cut both sides at once I think many here would have their jaw drop at how much runout and slop most of the machines in use have built up over years, or the lack of setup care that is taken by the 18 yr old kid doing it at your auto supply or local brake shop.

Common procedure is to hit the surface with a roloc abrasive disk on a angle die grinder while the rotor is turning after the cut, this is what makes the little circles. Most call it a "non-directional finish" LOL I'm sure a seasoned machinist on a well maintained brake lathe would be much different though. Either might be hard to justify with many new brake rotors being available for $20 nowadays though?

If you want to do it to do it....do it...., If youre just trying to get your brakes done new rotors is likely the best option IMHO unless were talking a 1 ton or larger truck ...Just my 2 cents Todd

William Brooks