Can someone explain ANPT to me?

[Jeff]

From my research it's Army and Navy specs but I can't find any actual dimensions.
We have to do an 1/8-27 ANPT internal thread. What is all of this L1 L3 stuff? 6 step, etc...
All we have are normal NPT plug gages.

[HTM01]

From my research it's Army and Navy specs but I can't find any actual dimensions.
We have to do an 1/8-27 ANPT internal thread. What is all of this L1 L3 stuff? 6 step, etc...
All we have are normal NPT plug gages.

Aeronautical National Form Taper Pipe Thread Plug Gages per SAE AS71051. ANPT thread plug gages are intended for use on pipe, plugs, fittings, and similar devices in aeronautical components and equipment requiring a sealed thread joint and where straight threads and gaskets or O-rings are inadequate.

[BrianP.]

The L1 and L3 are for the gauge. It will have 2 flats on it and you must stay between the flats for proper depth. This will ensure the fit that they want.