***Note*** 1/8PT and not 1/8NPT

After receiving advice on here I bought an LMA067 (M18x1.5 to 1/8NPT) in preparation to fit my on order defi oil temp gauge.

However, the gauge has come with an 1/8PT sender..!

Not a major deal and it seems I have several options..:

1. Defi do a 1/8NPT sender (#PDF03905S), but at ~£30 it's a bit steep..!
2. Defi do a 1/8PT to 1.8 NPT adaptor socket (PDF00708G), cheapish, but I'm not too happy about having to use 3 adaptors in total, IYSWIM..!
3. Apparently, Subaru do an exact adaptor (part #
11024AA210) that allows 1/8PT to be fitted into the M18x1.5 block plug..

Can anyone please confirm that this 3rd option is the case..?

J

 

LOL what the hell is 'PT'? Every single gauge manufacturer in the world uses standard 1/8NPT, so Defi have to use something different...what a pain in the ****, and it smells of Defi trying to rip hapless punters off even more than they already do by forcing you to use their own proprietry fittings.

With oil temp coming from where it does on top of 3 cylinder, you want to keep away from stacking adapter after adapter. Get the Subaru one if there is such a thing. I'd imagine there is, check the part number with a dealer and see. Or get LMA to make you one up, which I know they can do if necessary.

 

Apparently if you buy the imperial gauge you get 1/8NPT..!

Still trying to confirm that the Subaru one is 1/8PT.

LMA will probably be the best/cheapest bet, awaiting email reply..

I'm amazed nobody else has had this problem, it's not like there's not many defi's in metric out there..!

 

Nope, not so. The SARD regulator uses a 1/8PT screw fit adaptor for its setting gauge. I couldnt track down a 1/8PT adaptor anywhere. Maybe it is a japanese manufacture thing.

 

Weird. My SARD regulator (which is genuine) uses a 1/8NPT on the spare port. I know because I've got a 1/8NPT gauge screwed into it, with no leaks. In fact the instruction schematic even shows it as 1/8NPT.

 

Well that is strange Silent Running because mine (also genuine) is definitely 1/8PT on the guage port and my instruction schemetic shows differently to yours. It shows 1/8NPT on the two fuel nipple adaptors and 1/8PT on the guage. The 1/8NPT adaptor has a wider thread that the 1/8PT and it wouldnt fit on mine.

 

I've got to say, I've never heard of the "PT" thread abbreviation at all, neither have any of the engineering scales I have here, so quite what it is they've done or called by that abbreviation is anyone's guess?

Is it a tapered thread on the sensor, if it is, I'd wager it is actually NPT (National Pipe Taper). We've never seen anything other than NPT sensors here, and we do get through "a few".

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Threads according BSi - British Standard Institute - BS 21 "Specification for pipe threads for tubes and fittings where pressure-tight joints are made on the threads" can be made as

• parallel (straight) threads
• taper threads

Parallel (straight) Threads

BS parallel threads are also referred to as British Gas, British Pipe Parallel or Parallel Fastening Thread.
Common symbols used for the thread: BSP, BSPP, BSSPI, BSPF, BSPG, PS, Rp, G
The BSPP (parallel) male will mate with a BSPP (parallel) female or a female port.
Usually marked: G size ISO
Taper Threads

BS taper threads are also referred to as British Standard Taper Pipe, Pipe Taper or Conical Thread.
Common symbols used for the thread: BSPT, BSPTr, PT, KR, R, Rc
Usually marked: Rc size ISO
Characteristics of BSPT taper threads:

• tapered thread 1o47'
• truncation of roots and crests are rounded
• 55o thread angle
• pitch is measured in threads per inch
• taper is 3/4" per foot or 1 in 16 on the diameter

 

And, I've found it now.
PT - JIS Taper Pipe Threads
PT threads are functionally interchangeable with BSPT threads. This is an old designations replaced with and R and Rc.

Applicable Standards

JIS B 0203 TAPER PIPE THREADS
ISO 7/1 PIPE THREADS: DESIGNATION, DIMENSIONS/TOLERANCES

And it's clear they are slightly different, 1/8NPT is a 27TPI item, "PT" appears to be the same as BSPT which is a 28TPI item.

Maybe use a thread gauge to check whether 27 0r 28TPI, if 27 it's NPT, if 28, you'll need a BSPT adapter.

 

Ah, some light at last, cheers Mike..

I've got a LMA 067 adaptor in 1/8NPT (had it in ready to fit..) and the 1/8PT sender screws in, but binds (finger tight) with around 3mm of thread remaining..!

LMA are looking into it for me, so hopefully they can knock something up.

Other than that, I'll probably have to bite the bullet and buy the defi 1/8NPT sender..!

Mike, what's this BSPT adaptor..?

 

What I meant was, if you measure the thread and are sure that it's not NPT, that you may have more luck finding an adapter if you tell people that it's a BSPT thread (as opposed to calling it "PT").


Mike

 

Ah I see, it's definitely not 1/8NPT and also tapers, which is why it starts screwing into the 1/8NPT adaptor I have, but binds tight before seating properly.

Are all BSPT threads tapered..? This is the only thing I now unsure about..

Can anyone confirm what size the Subaru part (11024AA210) 'Main gallery plug' is..? I've heard it's 1/8PT, however as I've already been wrong I'd like to know for certain..!

I can see I'm going to have to bite the bullet and buy the 1/8NPT sender @ ~£30..

 

Right, just done some digging..

Both are tapered threads:

NPT 60° taper 27tpi
BSPT 55° taper 28tpi

So thanks to Mike.. I'm getting somewhere..

 

Right, it turns out that it fits after all..!

As they're TAPERED threads the sender isn't supposed to screw completely home, as long as there's at least 4 thread lands in contact.

Mine screws virtually all the way in, leaving just 2 threads exposed. I thought they had to seat right up to the flange..!

Many thanks to Mike and the guy's at LMA for the info and clarification..

 

LOL, just keep an eye on it once fitted anyway Jason.

The seal is caused by the deliberate deformation of the thread form, (The contoured part of the actual thread), don't over tighten it either, or it will gall the thead and allow a spiral leak path to develop which cannot be resolved by additional tightening.


Mike

 

Yep, will do..

I take it a little PTFE (sp?) won't hurt..?

Finally, do you think that the sender's long enough to take an accurate reading..?

Thanks again,
J

 

Yeah, that's long enough, a little PTFE can only help, either that or some loctite thread lock and let it cure a while first?


Mike.