blued brake rotor--is it ruined?..maybe need a replacement

[tjp]

I lent a brake rotor to a mate and got it back blued and maybe ruined. (??)

If the metal has been over heated to be blued, is the rotor beyond use?

If so, I need a replacement since that was one of my two back up rotors.

If it's ruined, any one have a good used rotor they would part with?

cheers
tim

[keith0alan]

They are cast iron and will handle an amazing amount of heat. Check for warping and it should be fine.

[tjp]

They are cast iron and will handle an amazing amount of heat. Check for warping and it should be fine.

I should have mentioned that, using a straight edge, is appears to no longer be flat. I've not used any actual measurement tools but a straight edge shows what is shows.

[keith0alan]

Do some measurements as to thickness and warp. It is quite likely that once turned straight is will be too thin.

[redroadster]

The trouble when they turn blue is
It hardens the steel and the cutter bit will not cut smooth ...it skips
On drums ,$$$ ones. a machine shop can grind it out... also its called a dull spot, which grabs the brake material way more than clean cast iron and will pulse the brakes

[datsunrides]

I agree with other in that if it has a blue hue to it, it got real hot and at a minimum is probably warped. If it is still safely within the minimum thickness spec and is not heat checked, there is a possibility it can be resurfaced. Machine shop with experienced guys will be able to tell you if it will turn out.