M14 x1.25 to 1/8" NPT adapter .. What am I missing !?

[Wightsparks]

I have a pressure sensor/transducer with a M14x1.25 male thread on it, ie spark plug thread size. I also have a bunch of other pressure sensors that have 1/8" NPT male threads on - (ie same size as mechanical gauges). These 1/8"NPTs thread into all of the array of connectors and adapters I have for testing oil, fuel and air pressures - instead of mechanical gauges.
I'd like to use the M14 sensor instead/as well, so all I want is a female M14 x1.25 to male 1/8" NPT adapter. Can not find one anywhere! Other way round M/F is easy. Any idea if it's a common conversion by a different description, or if there is a UK co that sells adapters - google turns up nothing for me except pipe and that's all M14x1.1

 

[doubleboost]

I have a pressure sensor/transducer with a M14x1.25 male thread on it, ie spark plug thread size. I also have a bunch of other pressure sensors that have 1/8" NPT male threads on - (ie same size as mechanical gauges). These 1/8"NPTs thread into all of the array of connectors and adapters I have for testing oil, fuel and air pressures - instead of mechanical gauges.
I'd like to use the M14 sensor instead/as well, so all I want is a female M14 x1.25 to male 1/8" NPT adapter. Can not find one anywhere! Other way round M/F is easy. Any idea if it's a common conversion by a different description, or if there is a UK co that sells adapters - google turns up nothing for me except pipe and that's all M14x1.1

View attachment 341544

I would make you one no problem

 

[Agroshield]

I would make you one no problem

NPT is not only tapered, at that size it is 27tpi (https://torqbolt.com/npt-threads-national-tapered-pipe-threads-dimensions-specifications). That will not be so easy on a metric lathe unless you have a 1/8 NPT die.

You might do well to make something with an M14 female thread one end and a 1/8 BSP female the other. Then he can buy a male 1/8 BSP to male 1/8 NPT (£0.99 here http://pipefittingsdirect.co.uk/contents/en-uk/d123_NPT-Fittings.html) to complete the part.

 

[bricol]

Plenty in the USA, as you might expect - postage looks high though.

Metric M14 M14X1.5 Female to 1/8" Male NPT Pipe Fitting Gauge Adapter

1/8” Male NPT to M14X1.5 Female Metric Coupling Brass Pipe Fitting Gauge Adapter

www.fittings.space

Edit - although it would help if I could read - thats an M14X1.5 - sorry

 

[RonA]

Are you dealing with a BSPP thread, the parallel form of BSP? RonA

 

[Wightsparks]

I would make you one no problem

That would be fantastic - thanks @doubleboost ! Happy to supply beer tokens of course.
@bricol - yea £50 postage is a bit steep!

 

[doubleboost]

That would be fantastic - thanks @doubleboost ! Happy to supply beer tokens of course.
@bricol - yea £50 postage is a bit steep!

do you want it in brass or steel

 

[Maker]

NPT is not only tapered

I've never tried it myself, but it's possible to cut a tapered thread between centres. So far I've managed to get away with parallel threads and an extra turn of PTFE tape. I am tempted to go out and try it now.

 

[doubleboost]

just had a look the 1/8 tap i have is BSPTF 27 TPI
The thread you want is 28 TPI
I would think it would still do the job .
I can screw cut the 14 mill part no problem .
The other end would be fun .

 

[Agroshield]

I've never tried it myself, but it's possible to cut a tapered thread between centres.

It is quite tricky to set up for an exact taper (1 in 16 on diameter for NPT) between centres. A horizontally-mounted boring head in the tailstock can help and saves offsetting the t/s. It is not trivial to turn the stock to the correct diameter to begin with - hard to measure with anything with parallel anvils. If you are screwcutting by keeping the halfnuts engaged (Mr DB has a metric, gearboxed Harrison 140, for example - making it cut 27tpi will be interesting), you have the added difficulty of having to secure the drive dog in both directions to cope with the spindle reversing. Not so many UK-market lathes do 27tpi out of the box. On a Chipmaster, you need 2C and then a 2/3 gear ratio (44/66, 40/60, 36/54, 42/63). It is aggravation to check the fit as you have to remove the centre to put on the nut (or have a long spigot on the part being turned and leave the nut in place). Gauging a taper thread is quite tricky in itself. See also: https://en.wikipedia.org/wiki/National_pipe_thread

For the hassle involved, I'd buy a die or buy something with the male NPT thread already on it.

 

[Agroshield]

just had a look the 1/8 tap i have is BSPTF 27 TPI
The thread you want is 28 TPI
I would think it would still do the job .
I can screw cut the 14 mill part no problem .
The other end would be fun .

You must have a strange tap collection.

1/8 BSP is 28 tpi.

The part he wants is 1/8 NPT, which is 27 tpi.

 

[bricol]

just had a look the 1/8 tap i have is BSPTF 27 TPI
The thread you want is 28 TPI
I would think it would still do the job .
I can screw cut the 14 mill part no problem .
The other end would be fun .

? 1/8 NPT is 27 TPI

1/8 BSP is 28 TPI.

One will screw into the other with a bit of pipe dope and no sympathy, and seal at up to 200PSI (don't ask . . and don't tell LMCO) but nothing else will be happy being screwed into either afterwards.

I think you may have him backwards - he wants female M14, male 1/8 NPT

 

[Wightsparks]

do you want it in brass or steel

This is the only bit of the last few posts I understood.
Whatever is easiest to be honest!

I think you may have him backwards - he wants female M14, male 1/8 NPT

Yep, I want to use the big sensor in the little hole.

 

[Wightsparks]

Huge thanks to @doubleboost for the adapter - it's a thing of beauty. Ordered up a few X--->1/8NPT for extra flexibility of use.



Even got to watch it being made -

Thanks again John!