Thread type/size on 1990 water fuel separator?

[RIBW]

On the winter job list is replacement of the (probably original) water separator with a Racor 120AT, which has 1/4"NPT-18 ports.
There are several possible ways of connecting it to the existing tank pipe, one of which is to use the current separator fitting into a female adapter on to NPT. I did a quick and dirty measurement (in pouring rain) which indicates that the AF of the current fitting is 14.5mm (see photo), which, as I understand it, equates to 3/8"UNF (or SAE as some have it). Now the equivalent device nowadays is specified as having 1/2"UNF.

Can anyone advise? Were separators in 1990 fitted with 3/8" UNF or is my measurement way out or ........????

Obviously, I am trying to gather all the correct reassembly bits before dismantling!

Thanks in advance
Bob

 

[Pete7]

New ones sold by IMS, though don't remember paying that much last year when I replaced ours.

http://www.imsupplies.co.uk/fuel-decanter-with-stainless-steel-filter.html

Know anyone or an engineering firm with a set of thread gauges?

Pete

 

[RIBW]

New ones sold by IMS, though don't remember paying that much last year when I replaced ours.

Thanks Pete,
But I already have the Racor - same price as the unit you hotlinked, BTW.

Know anyone or an engineering firm with a set of thread gauges?

I have thread gauges but no access until the old filter is removed. I was hoping someone would spring back with an answer so that I could avoid having to hunt for bits after dismantling, turning a 1 hour job into a 1 week job

Cheers
Bob

 

[colhel]

You're right that a standard UNF bolt has an A/F of 9/16" (close to 14.5mm). But looking at the the picture, the thread doesn't look that much smaller than the A/F of the hex which to me looks loike the the hex is not an SAE standard for a bolt. Maybe a 1/2" UNF fitting would have a smaller hex than a bolt as it doesn't want to be tightened as much as a standard bolt? My GUESS looking at the picture and comparing the hex with what is visible of the thread is that it is 1/2" UNF.

PS. Did I mention it was a guess?

 

[RIBW]

But looking at the the picture, the thread doesn't look that much smaller than the A/F of the hex which to me looks like the hex is not an SAE standard for a bolt. Maybe a 1/2" UNF fitting would have a smaller hex than a bolt as it doesn't want to be tightened as much as a standard bolt? My GUESS looking at the picture and comparing the hex with what is visible of the thread is that it is 1/2" UNF.

Looking at the profile of an SAE (Old speak for UNF apparently) on the Cotswold Engineering website, I thing your 'guess' is spot on! I'm going to work on that basis and buy some 1/2" UNF to NPT fittings.

I did a bit of googling for some confirming data but found nothing so far. I'll post a reference if I turn something up.

Thanks for the thought.
Cheers
Bob