Tap size for a metric .9mm thread?

[rons]

A threaded connection from a paint gun made in Japan has a .9mm pitch (exactly as seen under high power vision).

In terms of English measurement:
The diameter is 0.369 for the thread.
25.4/.9 = 28.22

Tap: 3/8 - 28 ???

In terms of Metric measurement:
0.369 * 25.4 = 9.3726mm

Tap: 9mm - .9 ???

Ideas? If this is not a standard size was it made that way for a reason?

The connection (male) is on the bottom of a paint gun handle.

 

[Sean the Dog]

(Assuming diameter given is thread OD.)

OD is obviously too big for a 9mm thread.

I'd go with the 3/8-28. Difference is 0.0003" between 28TPI and 28.22TPI.

Either that or a bastardized size (possibly M9.5-0.9 ?) making it harder to copy, easier to buy from original source.

 

[Limy Sami]

TIP 1 -If you look up thread ''manufacturing tolerances'' etc etc in MHB you will find when translated in to actual measurements, some classes are nigh barn door fit.

Tip 3 - As told me by and old autosetter in the pipe and tube fittings game (i.e. high volume low margin), it was quite common practice that when new, taps are made maximum OS permissible for the tolerance class, likewise fixed dies were made as small as possible, ..............as were drills & reamers made as large as poss, and again lathe tools set as tight as possible - all in the interests of getting maximum wear before sharpening and resetting etc etc.

All of which means if you have parts from either end of the wear spectrum, establishing true sizes etc etc can be tricky

 

[Goff]

It is close to 1/8-28 BSPP or BSPT. Maybe try a fitting and see if it works.

 

[L Vanice]

It is close to 1/8-28 BSPP or BSPT. Maybe try a fitting and see if it works.

I discovered when working with a Nissan diesel engine around 1975 that the Japanese use the British pipe threads rather than the American threads, so 1/8 BSPwhatever sounds likely.

Larry

 

[rons]

Thank all of you. I will check this stuff out.

The paint gun is a Grex. Ok, it's really a airbrush. The handle has a fitting screwed on the male thread. The fitting has a female thread on one end and a mini-coupler
profile on the other end. Those mini couplers are pretty cool, about 1 inch long and .400 in diameter. The coupler (not shown) accepts tubing like SMC 1/4". I.m using
the black vinyl. Great stuff, cleans up with lacquer thinner, It does have some coil memory, who cares.


Tritium: (what a bad ass name)




Grex Airbrush - Tritium Series Airbrushes

 

[L Vanice]

Thank all of you. I will check this stuff out.

The paint gun is a Grex. Ok, it's really a airbrush. The handle has a fitting screwed on the male thread. The fitting has a female thread on one end and a mini-coupler
profile on the other end. Those mini couplers are pretty cool, about 1 inch long and .400 in diameter.

View attachment 303717

One of the Grex fittings on their website actually says 1/8" BSP. The others just say 1/8" F or 1/8" M, which is not helpful.

Grex Airbrush - AM2 - Mini Manifold - 1/8" BSP Dual Output

Larry

 

[rons]

Thank you.I hope I am not putting a burden on this website by showing pictures of airbrushes. I think they are pretty cool, especially the gravity types.
Here is another one that I own, It is made in Germany. To give a sense of scale I measured the top of the two support stands to be 6.5 inches. I would
recommend them both but the Grex has a bowl position that can be rotated 360 degrees. (The support stands were fun to make).

Colani

 

[rons]

It is close to 1/8-28 BSPP or BSPT. Maybe try a fitting and see if it works.

I tried a 1/8 - 27 tap. It appeared to work into the fitting for a short distance.
I examined the thread profile of the male fitting. The Peak is not rounded over like a BSPP. The top of each thread has a flat.
The thread has a straight profile. The female part has a rubber o-ring on the inside for a seal.

Probably a 1/8 - 28 NPS.

Thanks for the help.

This is the point where I would do a better job on a CNC lathe. Doing a small female thread into a hole with a square bottom to fit a o-ring is where I
ask if it's worth me doing a hack job with a manual machine, or worse, trying to get a straight thread into the end of the hole with a bottoming tap.

 

[gregormarwick]

I tried a 1/8 - 27 tap. It appeared to work into the fitting for a short distance.
I examined the thread profile of the male fitting. The Peak is not rounded over like a BSPP. The top of each thread has a flat.
The thread has a straight profile. The female part has a rubber o-ring on the inside for a seal.

Probably a 1/8 - 28 NPS.

Thanks for the help.

This is the point where I would do a better job on a CNC lathe. Doing a small female thread into a hole with a square bottom to fit a o-ring is where I
ask if it's worth me doing a hack job with a manual machine, or worse, trying to get a straight thread into the end of the hole with a bottoming tap.

1/8-27 is NPT/NPS, there is no such thing as 1/8-28 NPS

You have a G (BSPP) 1/8 with the major diameter undersize. Not uncommon if the threads are formed on tube which they often are on small consumer grade stuff.
Standard G1/8 tap is all you need.

 

[MattiJ]

I discovered when working with a Nissan diesel engine around 1975 that the Japanese use the British pipe threads rather than the American threads, so 1/8 BSPwhatever sounds likely.

Larry

Not only Japanese but pretty much rest of the world except Americas.
British pipe thread is the "norm" even in metric countries.

 

[rons]

1/8-27 is NPT/NPS, there is no such thing as 1/8-28 NPS

You have a G (BSPP) 1/8 with the major diameter undersize. Not uncommon if the threads are formed on tube which they often are on small consumer grade stuff.
Standard G1/8 tap is all you need.

A 27 tpi gauge is a positive no fit. After a length of 5 threads the alignment is off by 1/2 thread. On way a 1/8-27 will work.

If they have a CNC machine they can dial in whatever dimensions they want.

 

[gregormarwick]

A 27 tpi gauge is a positive no fit. After a length of 5 threads the alignment is off by 1/2 thread. On way a 1/8-27 will work.

Yes, I got that. Repeating myself, 27TPI is NPT or NPS. 28TPI is BSPP (standardised in the metric world as G). G1/8 is a completely normal and common thread, that also happens to be used widely in airbrush equipment. I know this because I've been through this recently with one of my employees who is interested in airbrushes.

 

[rons]

TIP 1 -If you look up thread ''manufacturing tolerances'' etc etc in MHB you will find when translated in to actual measurements, some classes are nigh barn door fit.

Tip 3 - As told me by and old autosetter in the pipe and tube fittings game (i.e. high volume low margin), it was quite common practice that when new, taps are made maximum OS permissible for the tolerance class, likewise fixed dies were made as small as possible, ..............as were drills & reamers made as large as poss, and again lathe tools set as tight as possible - all in the interests of getting maximum wear before sharpening and resetting etc etc.

All of which means if you have parts from either end of the wear spectrum, establishing true sizes etc etc can be tricky

The wear on the threads is pretty severe. I may have installed the fitting about 12 times.

Actually it's chrome plate brass and brand new condition. The piece is part number AD09 and the coupler with fitting is part number AD08.
They just call out the thing as 1/8"F.

Grex Airbrush - Quick Connects