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shaque
05-17-2004, 07:21 AM
Good morning people;
Has anuone turned brake rotors by fly cutting them with a rotary table on the milling maachine?
I want to try it, but would like some feedback. Seems to me that the circular marks would help with breaking in the new disks.
Jim http://bbs.homeshopmachinist.net//smile.gif

Mike Burdick
05-17-2004, 11:15 AM
Jim,

I would think that brake rotors are designed based on the the SMOOTH metal against the brake pad. If it was rough, like a fly cutter would leave it, the rotor would act like a file and in no time at all the brake pad would be used up!

Jason J
05-17-2004, 11:50 AM
Actually light macining marks aid in proper break in of the pads. Improper brake in (almost all are) can reduce braking power by 30% or so. Do it right and you will be amazed at how ell they work.

There is a reason that rotors are turned on a lathe. It keeps everything concentric and both faces of the rotor parallel. No such guaranty witha rotary table on a mill.

Paul Gauthier
05-17-2004, 12:03 PM
Yes I have tried it, however I was not too successful, I could not get the set up good enough to insure paralelism(sp?) of both sides and the locating surface to eliminate vibration when applying the brakes. So before I junked the rotors by removing too much material I set them up in my lathe. When turning rotors in the lathe one should face both side in one setup, this is not an absolute but it does insure paralelle(sp?) sides. When refacing rotors care must be taken to set up from locating surface. The locating surface is that surface which locates against your spindle hub.
You can make the surface smooth enough with a fly cutter, use a radius of .060" on the tip of your tool. Be sure to use a carbide tool.
I don't want to say it can't be done on a rotab., I am sure it can be, but I found it too much hassle.

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Paul G.

Mike Burdick
05-17-2004, 12:09 PM
Here's some more on the subject:

http://www.babcox.com/editorial/bf/bf110322.htm

Jerry B
05-17-2004, 01:44 PM
The problem with doing it your way is that the brake surfaces will not be parallel with the mounting flange.

The rotors should be mounted on a shaft that will keep the mounting surface at 90 degrees to the axis of rotation. Then the rotor is machined so the friction surfaces are also at 90 degrees to the rotaional axis and parrallel to the mounting flange.

Any other way invites viration when the brakes are applied shortening the life of the calipers and the steering components.

Joel
05-17-2004, 02:01 PM
The machining marks shouldn't pose a problem if kept to a minimum.
I can do it on a lathe, but my local shop does my rotors for $5.00, so it’s just not worth it to me.