G Thread?
G Thread?
(OP)
I have a block with a G1/4 thread in it. One person tells me this is a British standard thread. Another tells me it is a American standard. Could someone tell me what this G thread is so that I can get the correct fittings.
Thanks
Thanks





RE: G Thread?
RE: G Thread?
http://mdmetric.com/tech/thddat7.htm
RE: G Thread?
RE: G Thread?
The size designation (like 3/8") does not mean actual thread OD; it is the internal diameter of the pipe, on which it is used. To be more exact - the original internal diameter, because the pipes became thinner (better material, probably) but their OD's remain, for the exchangability purposes obviously.
This thread is internationally standardized. As EM mentioned, apex angle is 55 deg.
RE: G Thread?
RE: G Thread?
RE: G Thread?
The internal G thread is cylindrical; the external can be conical ("GCon")
RE: G Thread?
They will seal without an "O"ring if PTFE tape is used or if a thread sealant like Locktite 515 is used.
Some sizes (1/2" for example)can be used on NTP fittings if you are a bit rough about quality. The will often tighten up about 3 turns before binding. The mixed thread joints always leak unless you use a good skived PTFE tape or Locktite.
It's not good practice, but it will get you home.
Regards
pat
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: G Thread?
RE: G Thread?
RE: G Thread?
I agree. The "G" designation is used to denote a BSPP (British Standard Pipe Parallel) thread. This is described in the Machinery's Handbook. The tapered version is rather uncommon in Europe, and when used, is shown as a BSPT thread. If a BSP thread is shown, it is generally understood to be the parallel thread.
Sealing is accomplished with a bonded washer. A well-known trade name is the "Dowdy" washer.
Schlebb
RE: G Thread?
RE: G Thread?
The most pipe thread cutting machines cut the Gcon thread automatically (I worked with them for a while).
RE: G Thread?
RE: G Thread?
Just to show the weird places threads may lead - 'tow' is the stringy stuff associated with coaltar, used for rendering watertight the spaces between wooden planks in a boat's hull. Water-pipe joints are often rendered watertight with the same fibre, cut with a much longer fibre length, known as 'lead wool' or 'plumber's wool' Both tow and lead wool are products of that immensly versatile and useful plant, hemp.
RE: G Thread?
Now I know what I used to seal the pipes. We also used some kind of plumbers paste with it.
English is my n-th language, what means that I do not know any language properly. But I see that we are talking about the same "stuff".
Thanks again, happy New year to you and to anybody who will read this words!
RE: G Thread?
Is it certain that Gas threads are exactly the same as BSP? I haven't seen taps or dies labeled 'gas' for donkeys years, but I remember that they were in a seperate tin from the BSP stuff...
RE: G Thread?
RE: G Thread?
to BSPP parallel thread and uses a larger tap drill than
for the BSPT tapered thread.
http://websearch.cs.com/cs/boomframe.jsp?query=metric+p...
RE: G Thread?
RE: G Thread?
RE: G Thread?
Thread281-84751
Now all one has to do is refer them to your thread (which I did). If your thread were erased, that's what would waste people's time, since it would all have to be repeated!
RE: G Thread?
BSPP = ISO(G) = cylindrical pipe thread with 55°apex angle
BSPT = ISO(R) = conical pipe thread with 55° apex angle
Alex
RE: G Thread?
This is aal about pipe threads:
As far as I can check:
for example:
G 1/2 (for the female)
G 1/2 A (for the male thread add a tolerance class A(medium) or B(coarse))
means:
DIN ISO 228 Part 1: cilindrical male & female with nominal dimensions
This parallel thread is not used with a seal on the thread(use a sealing washer & flange)
or with other words:
apex angle= 55³
OD=20,955mm
TPI=14
or Pitch p=1,814mm
Thread Depth h=1,162mm
Pitch Dia d2=19,793mm
Root Dia d1=18,631mm
__________________________________________________________________________________
R 1/2 (for the male thread)
Rp 1/2 (for the female thread)
means:
DIN 2999 DIN 3858
WhitWorth pipe thread with parallel female(Rp) & tapered male(R) threads
This parallel thread is not used with a seal on the thread(use a sealing washer & flange)
or with other words:
apex angle= 55³
OD=20,955mm
TPI=14
or Pitch p=1,814mm
Thread Depth h=1,162mm
Pitch Dia d2=19,793mm
Root Dia d1=18,631mm
__________________________________________________________________________________
BSW-British Standard Whitworth for example 1/2"BSW
BSF-British Standard Fine for example 1/2"BSF
BSP-British Standard Pipe for example 1/2"BSP
(if BSP-British Standard Pipe Parallel is used it is in fact the same as: BSPP for example 1/2"BSPP)
BSPT-British Standard Pipe Tapered for example 1/2"BSPT
are all British Standards
and are not defined in the DIN or ISO norms as named above.
___________________________________________________________________________________
And I think I do not have to say that:
NPSM-National Pipe Straight Mechanical
NPSF-National Pipe Straight Fuel
NPT-National Pipe Taper
NPTF-National Pipe Taper Fuel
threads are all American standards.
_____________________________________________
So, I hope I helped with this.
If some one knows more let us know.
_____________________________________________
By the way:In Europe we use steel pipes and copper pipes as well for water as for gas,
depending on the kind of connections....
and , yes we use "hennep" and a kind of paste, but also "teflon"...
Greetings from Belgium (Europe).
RE: G Thread?
It's quit complex.
Let's look at the "G" and "R" used in these thread designation.
By all means we are talking about a Whitworth shaped thread.
apex angle=55³
And it's about tubes or pipes, that's also clear.
Where comes this "R" from?
I think it comes from the German word for tube(or pipe): Rohr.
Where comes this "G" from?
I think it comes from the word Gas or it may come from the German word for thread: Gewinde
Designation "R" is used in:
DIN 259
Whitworth pipe threads: parallel internal and parallel external threads, basic sizes
and is linked (in this norm) to the earlier named: ISO 228
(in which the designation "G" is used)
Designation "R" is also used in:
DIN 2999
Pipe threads of Whitworth form: parallel internal and taper external threads
DIN 3858 is linked with DIN 2999 and is also about
Pipe threads of Whitworth form: parallel internal and taper external threads
I also found an old sheet in which a BSP was also designated with that "R" and
also with KR(BSPT):
It seems that "R" as well as "Rc" is used for BSPT in BS 21 (British Standard)
Designation "G" is used in:
BS 2779 for BSP (BSPF)
NOTES:
In this forum I noticed a link:
http://mdmetric.com/tech/thddat7.htm
in which "G" is used for parallel Whitworth form threads: BSPP and BSPF
and where "R" is used for taper Whitworth form threads: BSPT
Look at this, different again(angle 60³ I think that this is a mistake):
http://www.maxbar.com/End_Fittings/DIN%20ISO%20228.htm
Our question is not new, see this forum link:
http://www.control.com/1026155238/index_html
And this is what i found also:
In March 2003 the British Standards Institute withdrew BS-2779 and replaced it
with ISO-228 (technically: BS-EN-ISO-228). The statement is that all requirements
for BS-2779 will now be filled with ISO-228.
So in the end, it's still not clear to me what is what.
The "G" en "R" are than used here, than used there, it's a kind of mixed up.
Greetings from Belgium (Europe).