Originally Posted by Smopho
White lead was not a thread locker, it is a high solid paint that can build up a surface and tighten clearances.
The best machined fittings are ones with a very high percentage of metal to metal contact between the mating surfaces-be it cylindrical engagement or in the case of a threaded assy, threaded engagement.
Years back white lead was used but it went the way of cork gaskets as adhesive technology outpaced their usefulness.
660 Quick Metal is designed to fill surface imperfections of cylindrical machined fits.
It's WAY too strong to ever be used as a threadlocker....everyone..consider yourselves warned.