Mounting the PIAB Suction Cup

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 (#2526A44), but that costs $28. IMO that seems kinda steep for just ONE lousy use! :frowning:

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…) :wink:

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”!) :smiley: But that’s soooo tacky, heavy, and prone to other failure modes.

Suggestions appreciated. Thanks!

  • Keith

I have a lathe, I don’t see what the problem is. Cut some threads in a piece of metal to fit the part. I guess if you don’t have a lathe, then you see the problem differently than I do.

If the 3/8 NPT tap happens to have the same thread pitch, and the conical tap happens to have the same diameter as the suction cup at some point along it’s length, you might consider making a thin nut from 1/4" aluminum stock. The threads will not be a perfect fit, but they could be close enough.

Well, until you know for certain where it will be placed you can just use a hot glue gun to make a nice seal. Once the suction cup is in place and you are certain of its placement you can use more permanent epoxy like JB weld.

No luck. That’s our problem: There are no lathes here. (A excellent suggestion though, for whenever we do get one!):slight_smile:

…and I hate to ask a sponsor to spend big bucks to have one of their machinsts go out and make one lousy nut. That’s one expensive nut!

Is that what your team is doing?

Other tricks, anyone?

(And before anyone says it, considering the thought time spent on this already I probably could have just gone out and bought the darn tap… But this is one of those “generic” problems that nag at you. I’d really like to find a better, simple solution for one-of problems like this than “go and throw money”, just for the next time something similar comes up. Thanks!)

  • Keith

PIAB sells T-slot adapters for their suction cups (you are using a standard automotive industry end-of-arm tooling system, right?) which seems like it would be easy enough to modify into a standard mount bracket.

Part number 01.04.111 (the G3/8") should be compatible with the FC75P.4E.07UF Suction Cup in the KOP. (Use email ‘[email protected]’ to access datasheets and CAD files.)

For quick reference:
PIAB part 01.04.111
Base: 1.25" square

you should be able to get a mating component at a local pneumatics supplier or distributer – festo, smc, bimbo, numatics, motion industries,…
find the right fit – do not use epoxy. you will suck something up and need to replace or clean the unit half way through the tourney. I recommend a spare in your pit kit.

The Kit of Parts checklist identifies the suction cup as PN FC75P.4E.07UF. According to the PIAB website, the male threads are G3/8, and not compatiblewith NP threads.


“Suction cup FC75P Polyurethane 60, G3/8” male - 1/8" NPSF female"

So that could be the problem, we need a G3/8" nut, not a NPSF nut. Good catch!

The G3/8 thread is a British straight pipe thread. It is 19 TPI, 16.62 mm major diameter.



Did you actually find a NPSF nut? if so, that would work as well. (As I said a the top, NPSF stands for “National Pipe STRAIGHT etc…” )

We haven’t been able to find a 3/8-18 NPSF nut anywhere locally. (You probably tried a 3/8-18 NPT [National Pipe Thread] connector. That is the TAPERED one - I mentioned above that we already know it won’t work. ) :frowning:

But that still isn’t my original question… What off-the-shelf solutions have YOU guys already FOUND, to mount this puppy? (Part sources, please) We’d considering the link (mentioned above) for the T-nuts, but that just converts the problem into one requiring a T-Slot holder. And, giving us the specs for the thread doesn’t help (we have that already), as we have no lathe here.

I guess I’d still like to hear other actual off-the-shelf solutions people have tried (which WORK, and hold it SECURELY), for those of us that do NOT have access to a lathe.


  • Keith

Off the shelf solution: get a very short 1/8" npt nipple, and an 1/8" npt coupler, and put the mounting bracket between them, and screw it together. You’ll have to mess around to get the spacing correct so the pipe threads tighten about the same time the bodys of the cup and coupler contact the bracket.

I can draw a sketch if you don’t understand, let me know

Buy a 3/8" shaft collar?

the G3/8" pipe thread is much larger than 3/8", but a 5/8" shaft collar might work.

With pipe sizes, the size is the nominal inside diameter…not like bolts, where the size is the actual outside diameter.

Oh, you’re right! I didn’t even think about the actual size of the vacuum cup. But that seem like the easiest option, should a tap not be available. You’d probably need to weld onto the collar, but it should hold the cup more securely.

Ummm, I may be making a fool of myself here, but I’m pretty sure our cup came with a nut, we used it to mount it to a metal plate for testing… :confused:


We found a nut for the PIAB suction cup mounting at the local hardware store, it is an electrician’s part. Not sure what it’s used for, but perhaps a electrical supply store can get one for you. Here’s a photo.

NOW we’re talking! Hmmmm. I didn’t consider mounting via the actual vac connection.

My biggest concern with that trick is adapting there may excessively increase the volume that has to be vacated by the Vacuum Generator (VG). That could slow the grip/release response, wasting precious air. But I’ll have to try this one! (Thanks!)

In fact, I may be able to simply sandwich a thin plate between the actual mini-hose connector and the cup (but I’m afraid there may be too few threads for that to be structurally sound).

Let’s keep the ideas coming though. Any others?

  • Keith

Given this inspiration, kids on our team put this together: