Mounting the PIAB Suction Cup

[kmcclary]

According to the specs, the PIAB suction cup has a 3/8-18NPSF (National Pipe Straight Dryseal) outer thread. That's not a standard tap in MY set! ...And FIRST didn't supply a mating nut for it (that I've noticed at least).

What are you guys doing for mounting this thing?

So far, I've tried:

- Sticking the end into the closest sized pipe coupler. Only a few threads go in before it jams. (Hmmm...) That's not secure enough for me.

- All of my local hardware stores only carry NPT taps in that size. (FYI, NPT = National Pipe Thread - That's tapered, not straight, to form conical jam seals in pipe connections. No joy...)

- I haven't found a mating nut for it. (IS there a mating nut somewhere?) A "3/8 pipe thread" does not take a 3/8" nut. It's slightly larger than a a 5/8" nut. (Darn...) Nothing fits in metric, either (worth the try though). I couldn't find one at McMaster. Googling "3/8-18NPSF nut" didn't work, either.

- I HAVE found a 3/8-18NPSF tap at McMaster.com (#2526A44), but that costs $28. IMO that seems kinda steep for just ONE lousy use!

So... Has anyone found a sneaky, cheaper way yet to mount the suction cup? I really don't want to fork out the bucks for the special tap! (Let alone store and then try to find the darn thing again in my tap collection a few years from now whenever we need to use a suction cup again...)

Personally, I'm currently leaning toward drilling an oversized hole in my mount, then filling the gap with some structural epoxy. (That should form a nice, strong, "threaded socket"!) But that's soooo tacky, heavy, and prone to other failure modes.

Suggestions appreciated. Thanks!

- Keith