NPT to BSP adapters - UK source

[jono]

Hi all,

My electric oil pressure sender for the +2 was missing so I have managed to obtain a second hand item from a Daimler V8 which I have been told will work (same operating range, so that offers some hope). However the Daimler unit is 1/4 BSP thread and I need to get from that to 1/8 NPT.

I can't seem to find a source - 1/4 NPT to 1/8 NPT is available and some BSP to NPT but not in the format I need.

Any thoughts as to a source? I'm going to try Think Automotive tomorrow and see if they can fix me up.

The only other thought is could I bastardise a 1/4 female NPT to 1/8 male brass bush (available) by effectively forcing the 1/4 BSP sender to cut its own thread and using some thread lock, bearing fit etc? Once its in it won't need to come out again.

Any advice appreciated

Jon

[oldelanman]

Hi Jon,
Have you tried these people.....http://www.speedograph-richfield.com/index.html
Look under "Instrument fittings" then "Oil Pressure Gauge Accessories"

Or maybe these......http://www.rdgtools.co.uk/acatalog/Airb ... ptors.html

[elanman999]

Jon,
It's a complicated way of doing it but :-
1/8 bsp to npt male adaptor, 1/8 to 1/4 bsp bush and a 1/4 bsp socket. From http://www.bearingboys.co.uk/Brass_Hose ... ors-1439-c
Cheers
John

[rgh0]

Be careful about a long string of adapters. I have seem them used on twin cams and seen them break from the vibration. If needed mount the sender remotly in the body and run a flexible line to it and put the adapters at the sender end fixed to the body with the minium components hanging on the engine

cheers
Rohan

[billwill]

If they are difficult to find, I would think your best bet is to locate a small machine shop and ask them to make one for you from Hex brass stock.

[elansprint71]

Remember there are two types of BSP thread, parallel and taper.

Actually it's more complicated than that, he said, reaching for Carroll Smith's "Nuts, Bolts, Fasteners and Plumbing Handbook".

[AHM]

Forgive my ignorance of most things +2, but which is the bit that is NPT?

I can't imagine Ford UK, Lotus, or Smiths going to the cost and effort of tooling-up for an obscure US thread ....even the europeans still use BSP/BSPT for some things.

... or I'll eat my hat!

[Kerryt333]

Hi Jon,
If I understand correctly , you just need to run a 1/4" BSP tap down a 1/4" NPT hole, as the parallel pipe threads are usually
slightly bigger on the effective diameter. If this is what's required just contact me , send me the fitting & I'll tap it out for you
f.o.c & post it back.
Regards
John

[Kerryt333]

Have just checked ,& the tapping size for 1/4NPT is 11.1mm, 1/4"BSP is 11.8mm, & although they are different tpi ,18 to 19,
I would think a good enough thread would be obtainable for an oil sender unit.
Let me know if you want it done.
Regards
John

[jono]

Hi all,

Many thanks for all your suggestions and kind offers.

Just to be clear, the sender unit has a 1/4 BSP parallel male thread and the brass slug into the engine block has 1/8 NPT taper female thread.

I have found a 1/4 NPT male to 1/8 female adapter online which I have ordered. It's in brass so I am going to see if the sender will cut it's own thread into the new brass bush or else if it can be re tapped to a parallel BSP thread. Bit of a botch I know but with some industrial adhesive in there it might just work.

If this fails I may be back to take up some of the kind offers of assistance from the engineers out there!

The reason for all this palaver is that I converted to a capillary gauge but the Goodridge hose I got from Think Automotive would not fit into the cramped area at the back of the dash, even with a 90 degree fitting.

Cheers

Jon

[elansprint71]

If you have a male 1/4 BSP parallel thread on the sender, why not just tap the block (or insert) with 1/4 BSP and use some sealing compound?

Incidentally, I have been in engineering in the UK since 1968 and not once have I come across an NPT thread.

[AHM]

Just to be clear, the sender unit has a 1/4 BSP parallel male thread and the brass slug into the engine block has 1/8 NPT taper female thread.

For my benefit, and before I eat my hat! I find it inconceivable that a UK manufacturer would cut UNC and BSP into the block and then throw in an obscure one....

Edit
If I understand correctly it is the brass connector that has the NPT thread for the sender. In which case take it out and replace with the correct one - probably BSP to BSP. Which are easy to get and cost pence.

[jono]

Chaps,

In view of your replies it would seem most likely that what I have is in fact a 1/8 BSP taper thread and a 1/4 BSP parallel thread. When I obtained the capillary tube and adapter bush from Think Automotive they supplied a 1/8 NPT bush (definately, I have the receipt!) which fits 'perfectly' into the brass slug in the block but perhaps that is in fact a BSP taper in the slug which just happens to provide an acceptable fit to a NPT taper thread?

I would not wish to tap the block of a freshly built engine for fear of getting swarf into the oil galleries and in any case this would mean the sender would foul on the heater hose outlet.

So, 1/4 BSP parallel to 1/8 BSP taper would seem to be what I need

Jon

[AHM]

I'm slightly confused as to what you have.

1/8 NPT/BSP are not compatible

What you should be trying to achieve IMO is to go from the hole in the block to the sender with just 1 connector 'slug' . With no tapping, drilling, or bodging!

[jono]

AHM

It always surprises me that it's the most innocuous threads that appear to gain 'legs'

Anyway, this is what I thought I had:

Brass slug into block - 1/8 NPT male taper thread into block with 90 degree 1/8 female taper thread in side of the slug

Daimler V8 oil pressure sender - this is definately a 1/4 BSP parallel thread

The reason I was given to understand that the oil take off thread is 1/8 NPT is that Think Automotive suggested or told me that it was. They supplied me with a bush, allegedly 1/8 NPT, which was a perfect fit into the slug. On that basis I have formed the opinion that the threads associated with the oil take off are NPT. Odd I know but I assumed it was possibly to do with American DNA infiltrating Ford UK

I suspect that whilst NPT and BSP threads are obviously different that in practice they might 'work' especially in soft brass - time will tell when the bush turns up and I will report further when it does!

Thanks again for all comments

Jon