QUOTE(porsche735 @ Oct 12 2003, 03:38 PM)
...I have to install 1/2" NPT to AN-12 fittings into my Mocal Oil Thermostat Sandwich plate. What torque should I use and what goop should I use if any? ... what torque do you use on aluminum AN-12 fittings?
i usually use LocTite's "Pipe Sealer With Teflon" (PST).
but i've been known to use other Moly-based anti-sieze compounds with NPT threads. i turn them in until they get a little tight, loosen 1/8 turn, tighten some more, loosen some more - you are using each part to form the threads on the other, burnishing down high spots - most of the female threads in aluminum castings leave much to be desired in terms of smoothness.
NPT fittings seal by their taper, and do not require horrendous torque to seal. just get them 'tight' and you should be fine; in the event of a tiny leak later, you can try a little more torque. i've never had to re-tighten anything more than once...
similarly - AN fittings seal by virtue of the cone on the flare, and require torque only sufficient to keep the B nut in place. snug will do. i still treasure my set of aluminum Bonney wrenches, color-code anodised for the matching sizes.