Dusty
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| posted on 15/3/06 at 10:38 AM |
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Thread sizes
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?
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britishtrident
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| posted on 15/3/06 at 10:41 AM |
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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
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flak monkey
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| posted on 15/3/06 at 10:57 AM |
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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]
Sera
http://www.motosera.com
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Hellfire
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| posted on 15/3/06 at 11:12 AM |
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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.
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flak monkey
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| posted on 15/3/06 at 11:14 AM |
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I read it as theres a blank hole drilled in the rail, ready to be tapped....
Sera
http://www.motosera.com
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Dusty
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| posted on 15/3/06 at 11:45 AM |
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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]
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flak monkey
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| posted on 15/3/06 at 12:01 PM |
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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
Sera
http://www.motosera.com
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NS Dev
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| posted on 15/3/06 at 12:01 PM |
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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!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Nick Skidmore
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| posted on 15/3/06 at 03:51 PM |
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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
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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Syd Bridge
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| posted on 16/3/06 at 10:18 AM |
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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]
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NS Dev
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| posted on 16/3/06 at 11:36 AM |
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...............my thoughts exactly, but if it is a 5/8" blank hole then it's not, which is confusing!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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