Obscure Thread

[simondavies3Participant @simondavies3]

Another one for collectors and aficionados of obscure threads….I bring you “Garden Hose Thread, or GHT.
(And I am well aware that that sort of comment will produce a deluge of messages telling me that it is not at all obscure, however it is to me.)

 

My wife purchased two lengths of “sprinkler hose”, flat section hose with 3 channels and pierced on both sides for watering a specific area. She was dismayed to find that they didn’t just ‘connect’ and that she had to pay yet another £15 or so for the adapter. I agreed to ‘sort something’ assuming that the end cap on one hose was simply a 3/4 BSP, as most things are around here. Actually the diameter seemed ok – but not the thread. On closer examination, the thread didn’t fall into any of the imperial thread gauge options (11, 12,13 or 14TPI), nor the metric alternatives (1.75, 2 or 2.5mm).
A manual count and measure suggested around 2.25mm……which is suspiciously close to 11.5TPI. Further communication with Mr. Google revealed Garden Hose Thread, 1 1/8 by 11.5TPI….

One lump of brass and the ELS later (thankfully it had 11.5TPI as an option) and we have an adapter – as below.

 

So now you know…..

[JasonBModerator @jasonb]

11.5 is NPT The American pipe thread. Just like BSP it is based on the bore and not the OD

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, yep, it’s 1″ American National Pipe thread. Straight is N.P.S, taper is N.P.T., both of which taps and dies can be had from Tracy Tools and others in the UK.

Regards Nick.

[Julie AnnParticipant @julieann]

So that’s why my (manual) lathe has 11½ tpi listed as standard.

Julie

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Julie, 11.5 covers 1″, 1 1/4″, 1 1/2″ & 2″  N.P.T/S. threads.

Regards Nick.

 

[JasonBModerator @jasonb]

Would also explain why Simons US based Clough42 ELS has 11.5 tpi as standard. 😉

Chinese OEM ELS have a “custom” option for you to enter any pitch even if it is not listed under the common imperal pitches. I suspect they can set the default list of common pitches depending on where in the world the lathe is being shipped to. Same with the changewheel machines My Weiss based one has 11tpi but the ones for the US market 11.5tpi

[simondavies3Participant @simondavies3]

Thanks Jason et al, no clue why it didn’t immediately come up as US NPT – too quick to accept the info from my phone I guess:

 

Anyway, looks like it woke everybody up this morning… 🙂

[Ian PParticipant @ianp]

Simon, how do each side of your adapter seal?

Ian P

[Julie Ann]

On Julie Ann Said:

So that’s why my (manual) lathe has 11½ tpi listed as standard.

If an unidentified lathe appears, some clue to its origin or perhaps the market into which it was sold can be gained from whether its gearbox provides 11 1/2 tpi or 19tpi threads, as the Atlantic divides the user base.

A lot of the Colchester lathe manuals use 11 1/2tpi as a worked example for their ‘calculation of pitches not available from the gearbox’.

Brian Wood’s book shows the plate for the export version a Myford gearbox which substitutes 11 1/2tpi for 9 1/2tpi (19/2) but elsewhere (incorrectly) suggests that 23 tpi is used for US pipe threads.

[DC31k]

On DC31k Said:

On Julie Ann Said:

So that’s why my (manual) lathe has 11½ tpi listed as standard.

…whether its gearbox provides 11 1/2 tpi or 19tpi threads, as the Atlantic divides the user base.

My lathe must be floating mid-Atlantic as it has both 19 and 11½ tpi.

Julie

[Nigel Graham 2Participant @nigelgraham2]

That be for the Falklands, Tristan da Cunha, Azores and Iceland markets, then…

Curiosity led me to explore the Tracy Tools poster that lives next to my computer….

It shows plenty of prime-number TPIs listed but all except two are integers, among the common standard threads.

The fractional ones are both only on American threads:-

– two at 4.5 TPI (2 and 2.25″ UNC) and

– four each of the 11.5 TPI (1 to 2″ NP Standard and Fine, Parallel and Taper, threads).

So “garden hose thread” does not really exist as such – its name is just a selling convenience. Unless perhaps it is a standard US thread but of more rounded profile to suit plastic fittings??

After all, there are the standard bottle and lamp threads with heavily rounded profiles, Schrader valve threads, oil-well casing threads, the Dardalet self-locking, Buttress, Lowenhertz, ISO-M’s rather non-patterned coarse and fine series ….. and of course our very own ME series.

[Ian P]

On Ian P Said:

Simon, how do each side of your adapter seal?

Ian P

There is a rubber-like sheet washer that the end of the connector either buts up to inside the fitting – or in my case, buts up against the end of the corresponding hose adaptor.
Exactly the same as the flat rubber washers in tap adapters.

 

 

On Nigel Graham 2 Said:

 

 

So “garden hose thread” does not really exist as such – its name is just a selling convenience. Unless perhaps it is a standard US thread but of more rounded profile to suit plastic fittings??

Nigel, I just plucked the info from the website I snipped from above and it gave no suggestions that it was adapted for plastic or anything else…

[Russell EberhardtParticipant @russelleberhardt48058]

Hmm, my old Atlas lathe came with a 46 tooth change wheel (11.5 x 4).  Never used it.  Now I know why.  No need for an ELS in the 1950s|

Russell

[old martParticipant @oldmart]

The Smart & Brown model A has 27 threads as standard with the basic change wheels, and I got some more including a 120-127 to make the common metric pitches possible. Getting an 11.5″ tpi would be much easier on the Atlas 12 X 24 which has 55 combinations in its screwcutting QC gearbox without changing any wheels, and 11.5 is one of them.

[Author]

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