1988 mercury sable rear brake drums

I just replaced the rear brake shoes no my sable along with a set of new drums. I could not turn the rear drums after instalation. I put my old drums back on and took the new drums back to have them machined down a little bit. The parts guy told me the new drums were out of round. After removal of the new drums i did notice that the surface around the bolt holes was not flat anymore. My question is "what caused this?" Could it be the wheel studs are no good? The parts guy gave me a new pair of drums but i need to know what happened before i install the new drums. I tightened them by hand since i dont have a compressor. Any feedback will be greatly appreciated. Thanks a lot

 

Use a good quality drum not a cheap made in Mexico or china but a American or canada made unit. and use a torque wrench.If you use a cheap set and overtorue they sure will warp.

 

If new drums have been stored on edge they will get out of round. Make sure your parking brake cables are backed off.