Great thread! And speaking of threads, I had a bone to pick with my two Milton inflators, one I bought new 30 years ago, and another that is about 10 years older than that one.
Both read about 5 PSI off, where if the inflator reads 40 psi, there is really only about 35 psi in the tire. I have gotten by over the decades by just "overfilling" via the inflator gauge, and checking with an independent dial sweep gauge.
I had no idea until reading Skin's post above that the inflator gauges were tunable. Thanks Skin! And thanks Swamp Cat for posting your confirmation, and about doing it twice. And thanks Mr. Pretty for posting the catalog page, because those red letters identifying 3/8 fine (24) thread explains why I couldn't thread any "normal" air chuck foots on the end of the hard pipe of the Milton inflator.
And now about those 3/8-24 threads: My inflators had dual foot tips, but they were not the straight foot kind. The back angles of the angled foot and straight foot are the same, but the straight foot (that meets OSHA regs per the catalog page above) kind has the forward valve inline with the hard pipe, rather than offset and in line with the back angled foot.
The tip that is inline with the back angle foot is cheaper to produce, as there is one part that bounces back and forth between two orings, and that's it. The straight foot kind, on the other hand, has to have two separate valve ends and oring set ups, since the forward foot is not inline with the back foot, and is rather in line with the hard pipe.
All of that gobbledy gook is to say that on both of my "mighty" Milton inflators, besides the pressure gauge reading being inaccurate... the angled feet also failed. The would leak air as soon as pressure was applied to the inflator. I put up with this irritation for years also, until the leaks began making it impossible to fill high volume, high pressure truck tires (over 95 psi). I decided to spend a couple of bucks to replace the heads with the straight foot style. Well, that couple of bucks turned into an entire tool box drawer full of inflator feet.
I think I stopped in every truck stop in the western United States... from Yellowstone to the Pacific Ocean, Canada to Mexico, I stopped at Pilot, Flying J, TA, Petro, Loves, and random holes on the side of the road... looking for that odd ball inflator that would thread onto my Miltons. Even Fleetpride. Anyway, long story short, all of the other inflator feet threaded the same. But not onto the Miltons.
I've got to get a better set of thread gauges rather than the cheesy stampings that come with the cheesy tap and dies sets that I have. My good taps and good dies I can only afford to buy one at a time, on a per project basis. So I had no basis for determining exactly what kind of thread the Milton's use. (Somehow, the internet didn't occur to me.)
When my local hardware store wiped out all of their Milton inventory, I assumed that Milton went bye bye, like many a former US manufacturer has in our Alibaba world. I now realize that Milton is still in business as "Milton Industries" and it looks like one can still get parts from them. I did not know that when I decided to run the proprietary Milton swivel hard pipes through a die to "correct" the threads in the inflator foot end to properly engage with every other inflator head in the industry that I found (except Milton).
I post this story hoping that it will help a future searcher. Fortunately, the old school Milton hard pipes are very thick walled (compared to modern imported inflator hard pipes), so my "correction" of the threads did not appear to compromise the integrity and pressure rating of the tubing. I might have preferred to keep everything "Milton", but I discovered another advantage of rolling my own threads to match the common industry standard (NPT)...
I could extend the hard pipe to a more usable length for inflating the inside dual rear wheel. Here's a photo of the hard pipe extensions I added to the Milton inflators, in addition the straight feet:
View media item 54520
