does this look like a well machined rotor to you? [56k biggish pics]

[Steve_T]

For what it's worth I machined my old man's rotors using the machine at TAFE. I didn't even know a 'rubber band' existed, but ended up with a perfect finish on the rotors (which were seriously grooved and heaps of runout to start with - had to literally machine to minimum thickness to get 'em right) and they have been working/feeling fine on the car ever since. This was only cutting one side at a time though and was a (probably very) old lathe so maybe new ones work different (?)

Those discs look like they either haven't been machined deep enough (hit minimum thickness??) to remove all groving or just used a very coarse setting (trying to do 'em too quick?)

[RegSpec]

Originally Posted by Mike Gayner

:rolleyes:

I've machined dozens of rotors and I can tell you from experience you can get a perfect finish without a rubber band. The rubber is designed for when you are machining drums and there is only one cutting blade in contact with the surface, which sets up a harmonic resonance through the drum. When there are two blades equally in contact with the rotor the harmonics cancel each other out and it works fine, if your machine is in good condition. I have never machined slotted rotors, so I wouldn't know if this still applies but I can't imagine why it wouldn't.

Agreed Mike, the rubber band is used for drums but for machining discs our Ammco drum and disc lathe has 2 spring loaded pads that contact each side of the disc and when combined with a sharp cutter and the correct speed setting it gives a top surface every time , regardless of drilled ,slotted or whatever pattern is on them.

[Mike Gayner]

I've never heard of those things but they sound like a good idea. When machining rotors there is always a very small amount of resonance through the disc but not enough to ruin the finish unless the disc is severely worn, in which case it is usually beyond repair anyway.