Had to go out to the truck to check, yep factory (Un-tapered)running thread, So why is it that feild threads are tapered? Hmmm...
344.28 Reaming and Threading.
All cut ends shall be reamed or otherwise finished to remove rough edges. Where conduit is threaded in the field, a standard cutting die with a 1 in 16 taper (3/4-in. taper per foot) shall be used.
And, I beleive this to mean running threads past the normal range to allow connection without an Ericson type 3-piece coupling?
344.42(B) Running Threads. Running threads shall not be used on conduit for connection at couplings.
Dave55, not sure if silicone chalk is not a reduction in conductivity. Noalox, and Penetrox are at least listed for Aluminum conduit, and the zink in them isn't reactive on steel. Often HD Corrosion-X or thread cutting oil used to cut the threads is enough to keep most water out.
[This message has been edited by e57 (edited 09-12-2004).]