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13G?

Puzzled by this Whitworth(?) thread

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John Brown 1815/06/2022 17:54:06
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I have a thread gauge whose Whitworth section has a thread designated 13G. What is this? I can't find any reference to it in tables of Whitworth gauge.

Bazyle15/06/2022 18:02:09
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I believe something like this has been mentioned before. The G is a reference to the German word for thread possibly Gewinde. 13tpi is American 1/2" UNC.

SillyOldDuffer15/06/2022 19:22:37
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Maybe to do with British Standard Parallel Pipe threads, Whitworth form, and prefixed 'G'?

JasonB15/06/2022 19:30:48
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But there is no 13tpi on BSP or G threads

Howard Lewis15/06/2022 22:08:15
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Neither BSW, BSF, nor BSP list 13 tpi as a standard, so unlikely to be a Whit form (55 degree )thread.

The only 13 tpi listed in Zeus charts seems to be 1/2 - 13 UNC, which will be 60 degree.

Howard

Nicholas Farr15/06/2022 22:37:46
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Hi, many Whit gauges include a 13 G one and while there are no standard Whit threads that are 13 TPI, 1/2" whit and 1/2" UNC threads can look similar especially if you don't have one of each to compare, so a 13 G one is handy to have to tell if you have a UNC one for sure.

Regards Nick.

duncan webster15/06/2022 23:41:34
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Someone once told me that the Admiralty had a system of threads with bsw form but slightly different tpi. The reason behind this was so that if a warship fell into enemy hands they wouldn't be able to maintain it. Just shows our built in superiority complex, those foreign johnies won't be clever enough to make special nuts and bolts

Hopper16/06/2022 06:31:17
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With today's cheap thread pitch gauges made in China, anything is possible. They quite possibly make the same gauge for BSW and UNC and just change the labelling. The gauge is for counting TPI not determining flank angle so they may well use the same gauge for both, which would mean a 13TPI to cater for 1/2 UNC ending up in both sets.

I have a set of feeler gauges of reputable mid-range quality brand (Kinchrome) made in China like everything these days, and a check with a micrometer (genuine Mitutoyo 40 years old)  reveals that many of the feelers are not the thickness marked on them. EG, the 2, 3 and 4 thou feelers are all the exact same thickness. Others are not the exact imperial thickness labelled, but the nearest metric equivalent. So, like I said, anything is possible these days with cheap tools or even not-so-cheap-to-purchase but cheaply made in China.

Edited By Hopper on 16/06/2022 06:34:13

Hopper16/06/2022 06:36:18
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Posted by duncan webster on 15/06/2022 23:41:34:

Someone once told me that the Admiralty had a system of threads with bsw form but slightly different tpi. The reason behind this was so that if a warship fell into enemy hands they wouldn't be able to maintain it. Just shows our built in superiority complex, those foreign johnies won't be clever enough to make special nuts and bolts

laughlaughlaugh Sounds about right.

But those foreign johnnies would struggle to work out the standard Whitworth system anyway, being born and raised on the entirely rational metric system!

Nick Clarke 316/06/2022 09:33:11
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Posted by duncan webster on 15/06/2022 23:41:34:

Someone once told me that the Admiralty had a system of threads with bsw form but slightly different tpi. The reason behind this was so that if a warship fell into enemy hands they wouldn't be able to maintain it. Just shows our built in superiority complex, those foreign johnies won't be clever enough to make special nuts and bolts

In a similar vein I have been told by a retired GPO Telephones engineer that the organisation preferred 3,5,7 BA screws etc to the more common 2,4,6 as it meant that fewer were taken for 'home' use.

Mark Rand16/06/2022 09:34:24
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Posted by Hopper on 16/06/2022 06:36:18:

But those foreign johnnies would struggle to work out the standard Whitworth system anyway, being born and raised on the entirely rational metric system!

Ah, but they will be familiar with the concept, since they use BSP for their metric standard pipe fittings! surprise

Andrew Johnston16/06/2022 10:00:22
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The OP doesn't say the gauge is 13tpi. The letter G usually refers to BSPP threads. Sometimes the nominal imperial size is approximated in millimetres. So I expect the gauge is for 1/2" BSPP. May be the OP can tell us if the gauge is 14tpi?

Andrew

Hopper16/06/2022 10:09:13
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On Chinese-made thread pitch gauges the letter G seems to have been substituted for TPI in recent times. A sort of metrification perhaps in that it does not refer to the dreaded inches? It does not seem to refer to BSPP as the gauges come in a full range of TPI's for all threads, not just BSPP.

But I see on googling around that German made Whitworth thread pitch gauges are marked G also, perhaps from as pointed out above in reference to the German word for thread which starts with a G.  Link

Maybe the Chinese just followed suit?

Edited By Hopper on 16/06/2022 10:14:02

Andrew Johnston16/06/2022 10:32:06
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Posted by Hopper on 16/06/2022 06:36:18:

.....entirely rational metric system!

The metric system is not rational but arbitrary, the same as any other thread system (except possibly BA which is based on a geometric sequence). Before, and during, WWII the French and German metric thread systems were different below 6mm OD. For instance the French used M3x0.6 rather than the international standard 0.5mm pitch. Use of M3x0.6 is still part of the JIS system in Japan, as I discovered when I made some new parts for a guitar for a friend of a friend last year.

Andrew

Nicholas Farr16/06/2022 10:51:54
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Hi, my M&W thread gauges don't have a G on them, but they do have thread sizes that each one is associated with and there is a 13 one in the set, but no thread size is given.

thread gauges.jpg

As far as a 13 one being the same as a 12 on cheap gauge sets, it certainly isn't for a couple of cheapies that I have which are probably made somewhere in China, but when compared to my M&W set, no difference can be determined by eye and match up very snugly.

12g#13g.jpg

Regards Nick.

SillyOldDuffer16/06/2022 12:26:00
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Posted by Hopper on 16/06/2022 06:31:17:

With today's cheap thread pitch gauges made in China, anything is possible. ...

I have a set of feeler gauges of reputable mid-range quality brand (Kinchrome) made in China like everything these days, and a check with a micrometer (genuine Mitutoyo 40 years old) reveals that many of the feelers are not the thickness marked on them. EG, the 2, 3 and 4 thou feelers are all the exact same thickness. Others are not the exact imperial thickness labelled, but the nearest metric equivalent. So, like I said, anything is possible these days with cheap tools or even not-so-cheap-to-purchase but cheaply made in China.

...

The symptoms of Hopper's 'reputable mid-range quality brand' feeler gauge strongly suggest a counterfeit. It's not reputable, mid-range, or quality!

Counterfeit goods haver been around forever, and aren't specifically made in China or a modern phenomenon. Birmingham, England was once famous for cheap fakes, as later on were the USA, Germany and Japan.

Sadly, there's always someone, usually in a developing economy, who is prepared to make a quick buck out of making fakes. Worse in my opinion are folk in the developed world ready to dishonestly sell them on. Most of the profit is made by them, not the manufacturers, so the master criminal who needs a damned good flogging might be your next door neighbour, not a disreputable foreigner.

Unusual to find cheap fakes being made in developed countries because there's not much profit in producing them, unlike selling to victims!

China will follow the usual pattern: as wages and standards rise, fake making will move to other countries new to manufacturing.

Dave

Hopper16/06/2022 12:44:46
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Posted by SillyOldDuffer on 16/06/2022 12:26:00:
Posted by Hopper on 16/06/2022 06:31:17:

With today's cheap thread pitch gauges made in China, anything is possible. ...

I have a set of feeler gauges of reputable mid-range quality brand (Kinchrome) made in China like everything these days, and a check with a micrometer (genuine Mitutoyo 40 years old) reveals that many of the feelers are not the thickness marked on them. EG, the 2, 3 and 4 thou feelers are all the exact same thickness. Others are not the exact imperial thickness labelled, but the nearest metric equivalent. So, like I said, anything is possible these days with cheap tools or even not-so-cheap-to-purchase but cheaply made in China.

...

The symptoms of Hopper's 'reputable mid-range quality brand' feeler gauge strongly suggest a counterfeit. It's not reputable, mid-range, or quality!

Purchased in person from my local official Kinchrome tool dealership bricks and mortar store, so I am quite sure they are not fake.

Just another example of the well documented "quality fade" common in Chinese manufacturing, where Chinese suppliers start out supplying goods up to the client company's standards, but over time the supplier gradually substitutes cheaper and cheaper materials,methods and standards to maximise their profits. It is widespread and a well recognised problem. So much so that whole books have been written on the subject. Read it and weep LINK

China may well not rise above such practices in time. As the link outlines they have a fine history of sabotaging their own industry with such practices, which allowed Japan to take over the burgeoning 19th century silk manufacturing trade as China's reputation grew worse despite massive growth in the industry, thanks to deliberate quality fade to maximise short term profits at the expense of longterm reputation. Today's communist system of centrally controlled authoritarian capitalism still puts pressure on factory owners in various ways to make money now, above all. There is no sign of it changing any time soon.

mgnbuk16/06/2022 13:12:23
1207 forum posts
72 photos

But those foreign johnnies would struggle to work out the standard Whitworth system anyway, being born and raised on the entirely rational metric system!

At my previous employment we reworked a wartime built (WW2) German crankshaft grinder where all the threads were Whitworth. The machine came with all it's original documentation, with b & w photos stuck to type-written pages. From the number of throws on the mounted crankshaft in the pictures of the set-up machine + the size of the machine, I supect that these were U-boat diesel engine crankshafts. The machine most likely came to the Uk as reparations.

The gauge is for counting TPI not determining flank angle

I disagree - it is quite possible to determine the flank angle from thread gauges when held against the light. I have Unified, Whitworth & metric gauges at work for identifying threads, with the difference in "sight picture" on UN & WW threads of the same TPI being pretty obvious.

Nigel B.

Ian P16/06/2022 16:42:55
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2594 forum posts
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I have a thread gauge (bought in 1959) that has 'Whitworth 55deg' stamped into the side plate. the 26 different blades (4 to 62TPI) all have 'G' after the number.

As an example 12 TPI is marked 12G 1/2 9/16 but 13 TPI just has 13G (no diameter/s) as have 19G, 22G, 25G, 26G, 28G, 30G, 62G

I'm not sure what the G means at all really

Ian P

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