Hatz Biplane Association

In other words, you could just order the Pem nuts S-0524-2 and be happy.
This is actually noted in the thread about plans descrepancies, a post By John on March 15, 2013 7:36 am

That’s why I remade mine to except the AN hardware. Just pointing out another discrepancy. You’re right, no need for those fancy nuts. I’m just glad I figured it out before it was all welded.

The DAR may frown on anything but AN bolts.

One way to look at it is that the nut only has to be held in place until the bolt is threaded in. The force is against the strap, not the tack weld. You could get away with regular AN345 nut. It will fit inside the 3/4" tube. Just tack weld it to the strap like the plan shows for the PEM nut.

If the purist is planning to use the PEM nuts on the compression tubes, the part number he describes requires a 5/16-18 threaded bolt. On the top wing plan sheet, he notes that an AN5 bolt is required to assemble. These are 24 pitch bolts.
I made my own nuts out of 1/2” diameter rod but tapped them wrong because I made them to the PEM thread and now I have to remake them. Not a big deal but should have researched earlier if I could have even got AN bolts for them.

Of course, you could also buy 5/16-18 bolts from McMaster-Carr that have a drilled head but I wanted to keep the hardware on my plane homogeneous.

Just my two cents,
Doug D
HC160