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Dusty - 15/3/06 at 10:38 AM

Can anyone advise. I have an american made fuel rail blank which is drilled with a through hole which measures 0.625"/15.8mm diameter for fuel inlet and outlet connectors.

I assume the hole is not a random size but for a specific tapping. Anyone any ideas what thread?

britishtrident - 15/3/06 at 10:41 AM

US made likely to be NTP --- are the threads tapered ? in which case it will NTPT

A quick Google should find the thread tables for NTP and NTPT

flak monkey - 15/3/06 at 10:57 AM

NTP is the tapered thread and NPS is the stright one. Though there are many different abbreviations used (NPT commonly instead of NTP or t'other way around...confusing eh?!)

Anyway to the point:
The hole is 5/8" diameter, which doesnt match to either BSP or NPT tapping drill sizes.

So in that case you have two options...

The closest NPT thread size is 1/2"x14tpi Which needs a 23/32" hole (18.3mm)

The closest BSP thread is 1/2"x14tpi. Which needs a 3/4" hole (19.05mm)

David

[Edited on 15/3/06 by flak monkey]

Hellfire - 15/3/06 at 11:12 AM

Typically some BSP and NPT threads are compatible. Especially when up in the bigger sizes... 1", 1.5" I used NPT female threads which accept BSP and NPT males and is accepted by the Petroleum Regulations 1987. I was always a little wary as the angles and thread depth are different. BSP is a Whitworth Form 55 degree, NPT is 60 degree and deeper form with sharper radii.

Some precision engineering shops will have thread gauges to verify your thread.

flak monkey - 15/3/06 at 11:14 AM

I read it as theres a blank hole drilled in the rail, ready to be tapped....

Dusty - 15/3/06 at 11:45 AM

Yup. All I have at the moment is a hole. I need to get it tapped and find fittings for it. I just assumed it was that size for a reason. i.e. it was made for a 3/4 npt or whatever

[Edited on 15/3/06 by Dusty]

flak monkey - 15/3/06 at 12:01 PM

Doesnt seem to match to any common NPT or BSP thread sizes as I said above... the ones I suggested are the ones you could use....

Remember BSP and NPT thread sizes are nothing to do with the diameter of the thread. They are the bore sizes of the pipe that the threads were originally designed to be cut on!

David

NS Dev - 15/3/06 at 12:01 PM

quote:
Originally posted by Dusty
Can anyone advise. I have an american made fuel rail blank which is drilled with a through hole which measures 0.625"/15.8mm diameter for fuel inlet and outlet connectors.

I assume the hole is not a random size but for a specific tapping. Anyone any ideas what thread?


To be honest it does sound like a fairly "random" size, not in terms of actual size but in terms of common tapping hole sizes.

None of the taper threads will tap straight into that, it will drill out to 1/2" npt which would be 45/64" (17.8mm ish) but I would guess that will be getting thin on the wall?

None of the UNF threads (which are used on JIC fluid fittings which are the industry norm) will fit either!

I know a fair bit about fluid connections and I have no idea I'm afraid!

Nick Skidmore - 15/3/06 at 03:51 PM

May be 5/8 UNF, so a JIC-6 fitting will screw in.

Try a bolt or tap of UNF size first, if it wont go in then it's probably NPT

Syd Bridge - 16/3/06 at 10:18 AM

If it's american, or any motorsport part, the chances of the JIC size as Nick pointed out, is fairly high. Industry standard.

Syd.


Sorry Nat, didn't see the 'drilled blank' bit.

Tap to 3/4 x16 for -8 fittings. Use a reducer then to get it down to -6 or 3/8 fittings and hoses/pipes.

[Edited on 16/3/06 by Syd Bridge]

NS Dev - 16/3/06 at 11:36 AM

...............my thoughts exactly, but if it is a 5/8" blank hole then it's not, which is confusing!