Procedure used to machine a rotor

NoGood · #1 (**permalink**) 03-21-2005, 10:58 AM

Hi, I have an assignment for school and one of the things I have to do is describe the procedure used to machine a rotor.

Can anyone explain to me step by step how machining a rotor is done?

Hotfingrs · #2 (**permalink**) 03-21-2005, 11:44 AM

Pretty straight forward process. Find the center hub that you need for your rotor. Put on the back piece then the front piece, and tighten it down. This is what keeps the rotor centered for the machining process. Next postion your cutters, there is one for the front surface and one for the rear. Turn the dial indicator in until it just starts to take off metal, do the same for the rear. Flip the auto feed and let it go completely across the face. Then see if all the grooves are gone, if not take a few more thousandths off. Repeat until the scoring or grooves are gone. The lathe has a course and fine finish. At first you use the course finish, then for a final cut use the fine finish.

Now, maufacturers have a minimun thickness for their rotor. After machining you have to measure the thickness of the rotor and see if it falls into the more than minimum category. If it's under the minimum, you can't put it back on the car.

NoGood · #3 (**permalink**) 03-21-2005, 12:11 PM

Thanks a lot man.

One more question- what instrument is used to measure drum out-of-round?

Thanks again.

Hotfingrs · #4 (**permalink**) 03-21-2005, 01:07 PM

You use dial calipers to measure the rotors.

TonyMadrid · #5 (**permalink**) 03-21-2005, 02:36 PM

The previous reply is absolutely correct.

There are however two types of lathes used to cut rotors. The more common one is a stand alone lathe designed specifically for cutting rotors, and there is also an on-the-car brake lathe that cuts the rotors while they are still mounted on the vehicle.

Regardles of what type is used, the process is still basically the same.

D-CEL · #6 (**permalink**) 03-21-2005, 03:27 PM

NoGood,

"Out-of Round" or "Roundness" is " the deviation from a theoretically true circle. This is commonly measured by mounting the item to be checked on a spindle and rotating the part. Test or dial indicators can be used (I like a test indicator myself). A caliper can be used to measure the deviation in diameter, however this will only show a two-point eccentric condition (out of round). It will not show a three-point eccentricity. Other critical (and often overlooked) dimensional components of brake rotors are flatness and parallelism of the faces.

D-cel

ItBites · #7 (**permalink**) 03-21-2005, 04:31 PM

NG,

Did you really mean out-of-round in Drum Brakes?

If so, you would use a dial gage or dovetail to measure out of round. Chuck the drum in the brake lathe using the correct collars to center the drum on the hub. Then spin the drum by hand while a dovetail or dial caliper rests against the friction surface. Out-of-round (more correctly "run-out") will show up as variation in the reading as the drum is turned.

Hope this actually answers the question you intended to ask...

NoGood · #8 (**permalink**) 03-22-2005, 07:25 AM

Thanks a lot guys.

This really helped.

trularin · #9 (**permalink**) 03-22-2005, 08:36 AM

I took the machine of a rotor as making a rotor, not resurfacing one.

If you are machining a casting to make it into a rotor, that is different from resurfacing.

What are you reporting on??

ridelikehell · #10 (**permalink**) 03-22-2005, 11:57 AM

NoGood,
I wont to the procedures as everyone else has covered it perfectly; but I noticed you are in ON, which school are you going to for auto?...Or is this a highschool tech class?

NoGood · #11 (**permalink**) 04-05-2005, 03:33 PM

No, I go to Mohawk.

Sorry, I missed your post.

Big-Foot · #12 (**permalink**) 04-05-2005, 08:07 PM

Just don't forget the vibration Damper strap or the bit chatter will setup a vibration frequency in the rotor that will destroy the surface.

Cal Metal · #13 (**permalink**) 04-05-2005, 08:48 PM

In the final analysis, the idea of resurfacing rotors is something that is done very little these days, particularly since most cars use a "non hub" design type of rotor which doesn't incorporate an integral wheel bearing inside the hub/rotor. I think the last set of rotors for my performance Neon ACR ran about $18.00 a piece. Typically, reconditioning rotors will cost $12.00-$15.00 in our area. For $3.00 more you can have everything new without approaching minimum thickness issues.

BlueRooster · #14 (**permalink**) 04-06-2005, 06:31 AM

When I was I kid(when I actually was a mechanic), we used to have to take rotors off to resurface them...dirty and a pain in the ass. I would love to see the machine that resurfaces with the rotor on the spindle.

Cal: in my Rover there is no resurfacing. The minimum clearances are way too tight. I wish replacement was even remotely close to those numbers in your Neon.

Dane

trularin · #15 (**permalink**) 04-06-2005, 10:56 AM

Cal Metal brings a good point to this discussion. $30.00 to turn to rotors at the parts store. $18.00 new for ones made in Pakistan.

On top of that, pads are life warranty. Auotzone records your purchase and will allow you to bring the parts back without a receipt.

Last four brake jobs, I did for $72.00 each and I used new rotors and pads in all of them.

cobrashoch · #16 (**permalink**) 04-13-2005, 09:21 PM

I just did brakes on my full sized Dodge custiom van w/antilocks.
@ autozone , rotors 96$ 2-ea.(Mexico), ceramic pads 47$$(required), Grease seal 6$
Rear shoes 27$, wheel cyl. kit 11$ turn drums 8$ ea.
I guess I will never be lucky to get those cheap brake parts I keep hearing about.
cobrashock