Is this thread NPT or BSP?

[tractor240]

Not sure if it's possible to know just from a pic. It's from a front axle grease hose. Made in UK tractor but they did use NPT for some things.
Thanks.

 

[ptsg]

Without any dimensions given, it's a bit hard but since it's a grease line, I would say it's 1/8" BSPT.

 

[MichiganIron]

Without any dimensions given, it's a bit hard but since it's a grease line, I would say it's 1/8" BSPT.

Count the threads per inch on the fitting. BSPP and BSPT Fittings have one additional thread per inch than NPT Fittings. Finer threads mean BSPP or BSPT.
Hope this helps.

 

[tractor240]

Without any dimensions given, it's a bit hard but since it's a grease line, I would say it's 1/8" BSPT.

There is a definite taper..... diameter goes from just under 10mm to just over.

 

[ptsg]

There is a definite taper..... diameter goes from just under 10mm to just over.

View attachment 5661903


View attachment 5662341

That matches the 1/8" BSPT. It's about 10.1 mm at the largest diameter.

 

[tractor240]

That matches the 1/8" BSPT. It's about 10.1 mm at the largest diameter.

Sorry, just realized the caliper wasn't zeroed so was out by .2mm. Actual thickest diameter should have been 10.33mm....if that makes a difference?

 

[ptsg]

Sorry, just realized the caliper wasn't zeroed so was out by .2mm. Actual thickest diameter should have been 10.33mm....if that makes a difference?

No, won't affect much. A 1/8" BPST thread machined to the correct specs will measure about 10.1 mm at the 4th thread, but there is always some variation.

 

[tractor240]

No, won't affect much. A 1/8" BPST thread machined to the correct specs will measure about 10.1 mm at the 4th thread, but there is always some variation.

You were right.
Don't know why I didn't think of it before..... just remembered I have a grease cartridge hose which I know to be BSP (that supplier has no NPT hoses on their website) and it fits perfectly. Many thanks.

 

[WinterDeere]

Sounds like you got it figured out, if you're sure the grease gun is BSP.

A thread guage would confirm, as BSP and BSPT are both 28 TPI, whereas NPT is 27 TPI, in the 1/8" sizes. Both have similar ~10mm diameter, depending on tolerance and where you measure on the taper.

 

[tractor240]

Whilst on the subject of front axle grease.....does anyone know what type of grease I should use?
I have moly, high pressure and general heavy duty.

 

[WinterDeere]

I've never had a tractor with a "grease hose", but we usually use Lithium Complex or Polyurea on trailer axle wheel bearings. My tractors have all been either 4wd with bearings lubed by front diff gear oil, or small garden tractors with zerk fittings.

Do be aware that if you're changing grease types, it may be wise to clean out all the old before charging with new, as there can be occasional compatibility issues between types and brands.