Been using 1 inch half couplers for elements for years no problems. I just cut a full coupler in half.
Just stop and think a minute a coupler has taper thread but they are inside the coupler not at the start. The thread at the start are about as straight as your going to get. The electric element is only going in two to two half threads.
You can screw up taping with a pipe tap and go to far and end up with no taper and all straight threads. Just take a look at a tap.
Here is a picture of half coupler tig welded to Tri half for removeable element
The half of the tri welds into the pot or keg. Just remove the clamp and the electric element and box comes off in one piece. No wiring to unhook. That last photo don't show the two taps the are welded to the element half tri that bolt to the box.