J
johnpipe108
Guest
In a previous post I identified 1/4 "Universal Air-Source" fittings and mating connectors as BSPP; I was wrong! :redface:
The "Universal Air-Source" 1/4 Female-swivel fitting found on traditional Thayer & Chandler, Binks, Badger, Paasche, etc. braided airbrush hose has a 1/4 NPSM (" ..Straight Mechanical") threaded hex-nut, though the "button" shape varies from one manufacturer to another! The reason has to do with our American National Pipe system; as it turns out, we don't have just two, but three NP standards; NPT, NPTF ("..Fuel-flow"), and NPSM! NPT does not have a 60deg. internal bevel at the mouth, but the other two do, so as to seal properly in a standard 1/4 Female-swivel fitting.
Here's a pix of some hose ends with "Universal Air-Source Connectors", and a standard 1/4 female-swivel:
L to R: vintage Paasche, with a shallow-bevel on the button, vintage Binks with standard 60deg. bevel-button (but unusual inverted bevel in nose and small, 1/16" bore), contemporary Iwata with "ball" shape button, industrial-standard female-swivel with 60deg. button. The problem for the airbrush manufacturer is that the only folks who know about NPTF and NPSM connectors tend to be engineers and users in hydraulics and related fields; the average American only knows about NPT, the common, everyday, hardware-store plumbing-pipe standard, and will try to connect the traditional 1/4 airbrush hose to this, hence the varied attempts to make the fittings "Universal!"
Here's a view of some 1/4 male pipe-fitting ends:
L to R: 1/4 NPT nipple from Harbor Freight, vintage 1/4 NPTF to NPSM adaptor, NPSM output on vintage canned-air adaptor, BSPP thread on NPT female to BSPP adaptor. Note the similarity between BSPP and NPSM; 1/4 NPSM has 18tpi, BSPP has 19, and they are only a few thousanths different in maximum diameter. A "Universal Air-Source" fitting can be screwed onto BSPP, but it takes a little wrench torque the first time, after which it will go on and off easily (at least, that's true for my Iwata hose; ymmv!).
A higher angle view, looking at the 60deg. bevel on all fittings except NPT:
Here is the older Badger 180-11 cylinder-head output, tapped 1/8 BSPT, and the factory-installed adaptor output is 1/4 NPSM:
"Now, it is 1/8" BSPM to 1/8" BSPM, with a 1/8" BSPF to 1/4"NPSM adapter included in the box. " That's quoted from a reply by one of Badger's compressor engineers (I believe the first "BSPM" is wrong and should read "BSPT."), and I think the 'M' means "Mechanical" as the official BSPP standard was once changed to BSPM, then to ISO-228, but the hydraulics trade has always called it BSPP!
I fitted up a quick-connect for my compressor, with a 1/4 NPSM Female-Swivel industrial standard adaptor, which mates and seals on NPSM and NPTF:
I still have a problem at the other end, where the hose from the compressor leads into the air-tank; I hope to have solved a troublesome air-leak from the swivel on one end of the Harbor Freight Polyurethane coil-hose by applying JB Weld epoxy; I don't need the swivel, I want the air-tight connection that doesn't bleed air slowly from the tank when I forget to close the tank-valve between airbrush-sessions!
So, that's what I have ferreted out and fixed up my system a bit.
Regards, John
The "Universal Air-Source" 1/4 Female-swivel fitting found on traditional Thayer & Chandler, Binks, Badger, Paasche, etc. braided airbrush hose has a 1/4 NPSM (" ..Straight Mechanical") threaded hex-nut, though the "button" shape varies from one manufacturer to another! The reason has to do with our American National Pipe system; as it turns out, we don't have just two, but three NP standards; NPT, NPTF ("..Fuel-flow"), and NPSM! NPT does not have a 60deg. internal bevel at the mouth, but the other two do, so as to seal properly in a standard 1/4 Female-swivel fitting.
Here's a pix of some hose ends with "Universal Air-Source Connectors", and a standard 1/4 female-swivel:
L to R: vintage Paasche, with a shallow-bevel on the button, vintage Binks with standard 60deg. bevel-button (but unusual inverted bevel in nose and small, 1/16" bore), contemporary Iwata with "ball" shape button, industrial-standard female-swivel with 60deg. button. The problem for the airbrush manufacturer is that the only folks who know about NPTF and NPSM connectors tend to be engineers and users in hydraulics and related fields; the average American only knows about NPT, the common, everyday, hardware-store plumbing-pipe standard, and will try to connect the traditional 1/4 airbrush hose to this, hence the varied attempts to make the fittings "Universal!"
Here's a view of some 1/4 male pipe-fitting ends:
L to R: 1/4 NPT nipple from Harbor Freight, vintage 1/4 NPTF to NPSM adaptor, NPSM output on vintage canned-air adaptor, BSPP thread on NPT female to BSPP adaptor. Note the similarity between BSPP and NPSM; 1/4 NPSM has 18tpi, BSPP has 19, and they are only a few thousanths different in maximum diameter. A "Universal Air-Source" fitting can be screwed onto BSPP, but it takes a little wrench torque the first time, after which it will go on and off easily (at least, that's true for my Iwata hose; ymmv!).
A higher angle view, looking at the 60deg. bevel on all fittings except NPT:
Here is the older Badger 180-11 cylinder-head output, tapped 1/8 BSPT, and the factory-installed adaptor output is 1/4 NPSM:
"Now, it is 1/8" BSPM to 1/8" BSPM, with a 1/8" BSPF to 1/4"NPSM adapter included in the box. " That's quoted from a reply by one of Badger's compressor engineers (I believe the first "BSPM" is wrong and should read "BSPT."), and I think the 'M' means "Mechanical" as the official BSPP standard was once changed to BSPM, then to ISO-228, but the hydraulics trade has always called it BSPP!
I fitted up a quick-connect for my compressor, with a 1/4 NPSM Female-Swivel industrial standard adaptor, which mates and seals on NPSM and NPTF:
I still have a problem at the other end, where the hose from the compressor leads into the air-tank; I hope to have solved a troublesome air-leak from the swivel on one end of the Harbor Freight Polyurethane coil-hose by applying JB Weld epoxy; I don't need the swivel, I want the air-tight connection that doesn't bleed air slowly from the tank when I forget to close the tank-valve between airbrush-sessions!
So, that's what I have ferreted out and fixed up my system a bit.
Regards, John