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Can anyone identify this thread.

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On a jap engine the exhaust outlet is threaded, it measures 2" or 50mm across the threads and has 19 threads per inch. Can anyone identify what it is please? 

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1 hour ago, wurzel said:

if you google 19tpi it comes up as 1/4 bsp its either a none standard thread or a different tpi count

cheers nick

This is the problem I'm up against. I've used a very accurate set of thread gauges to arrive at 19 threads per inch. Every chart I've used doesn't seem to make sense. Due to my job I have access to allmost any bsp fittings so it defiantly isnt it. Thank you for your thoughts. I would of thought that jap would of used something off the shelf but I'm dammed if I can work out what.

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Hi Gareth, your right that it is not the standard BSP size, as everything (normally) over nominal 1" is 11TPI. 

I presume the inclusive thread angle is 55 degrees?.

Is the Outlet a threaded insert, or part of a Casting?. I'm wondering if they machine cut the thread to a special size.

A picture would be good if you can provide one.

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Some of the threads on mG2 137 were like that , they turned out to be what are known as "cycle " threads from the bicycle manufacturing industry. Which would fit with 137 having a Sturmey Archer engine.

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Very unlikely to be Cycle Thread in that diameter. No reference table for Cycle Thread goes any where near 2" .

My guess would be a manufacturer's special.

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11 hours ago, Anglo Traction said:

Hi Gareth, your right that it is not the standard BSP size, as everything (normally) over nominal 1" is 11TPI. 

I presume the inclusive thread angle is 55 degrees?.

Is the Outlet a threaded insert, or part of a Casting?. I'm wondering if they machine cut the thread to a special size.

A picture would be good if you can provide one.

Hi Richard I'll dig a photo out when I'm next at the unit. It is part of the casting.

 

10 hours ago, expeatfarmer said:

Some of the threads on mG2 137 were like that , they turned out to be what are known as "cycle " threads from the bicycle manufacturing industry. Which would fit with 137 having a Sturmey Archer engine.

Thanks for the suggestion, I've been able to identify all the other threads as either bsf or bsw, just drawn a blank with this one.

 

3 hours ago, Wristpin said:

Very unlikely to be Cycle Thread in that diameter. No reference table for Cycle Thread goes any where near 2" .

My guess would be a manufacturer's special.

That's what I'm fearing, can't see why they would use a special thread.

 

12 hours ago, wurzel said:

is it female or male your after you may have to cut your own

 

It's a female thread that I need, I don't posses the skill to cut my own nut unfortunately.

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1 hour ago, expeatfarmer said:

Bicycle bottom bracket bearing cups are 2" and bigger>

Thanks for the information, i'll check it out.

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Don't know how old your engine is Gareth, but it look's like the low 250-650cc original early Jap engines onwards used the same size Exhaust Flange Nut?.

I don't know if Villiers made any chnges ?.

Could the TPI be 20?. and the outer dia across the threads be 2" or 50.8mm (actual). If so, then the Thread form could be BSF (0.0500" pitch and thread height of 0.032".

This will give a Core dia (or Tapping diameter) of 1.937" (49.2mm).

There appears to be a worldwide search by many for used versions, as the price of a new (manufactured) one is silly money. See this link where the numbers seem to merge ok if 20 tpi-

http://de.vintage-motorcycle.com/index.php?language=en&site=4&pid=24&id=26427&limit=0

They can be made!. 

     

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Hi Richard the engine is approx 1946, I believe this was before villiers involvement, I'll double check the threads when I back at the unit but I'm sure it was 19,  couldn't get any other of the thread gauges to match.

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