flak monkey
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| posted on 8/1/09 at 05:58 PM |
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Tapping my fuel rail....
My fuel rail has a 1/2" bore (12.7mm).
The question is what the heck should I tap it with?
3/8 NPTF is a 14.25mm hole, no problem, but I can't get hold of an NPTF tap... (got NPT, but no NPTF!)
3/8" BSPT is a 14.75mm hole, but with a major diameter of 16.66mm its getting a bit tight (2.5mm) on the wall thickness of my fuel rail.
Any ideas? This is one of the last jobs holding me up with my MS install 
David
Sera
http://www.motosera.com
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liam.mccaffrey
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| posted on 8/1/09 at 06:05 PM |
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Weld in a bung and drill and tap an M10???
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stuart_g
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| posted on 8/1/09 at 06:23 PM |
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As above or weld a nut on top of the hole.
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BenB
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| posted on 8/1/09 at 06:33 PM |
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Depends what the fuel rail is made out of....
An easy option would buy some 1/2" round bar (some on Ebay for couple of quid), drill a 8mm hole through a slug of it, epoxy it into the end of
the fuel rail, epoxy some 8mm copper pipe through the middle of the slug, epoxy or solder an 8mm plumbing olive onto the end of the copper pipe to
stop the hose blowing off.
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BenB
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| posted on 8/1/09 at 06:35 PM |
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If you don't like epoxy you could always use some technoweld or similar to friction braze the slug in. And you could always tap the slug to take
a hose barb if you don't like copper tube + olive solutions....
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ashg
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| posted on 8/1/09 at 06:54 PM |
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put it in the lathe and cut the thread. sorted
Anything With Tits or Wheels Will cost you MONEY!!
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flak monkey
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| posted on 8/1/09 at 07:11 PM |
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Should perhaps add that it is aluminium fuel rail extrusion, like this:
http://www.rossmachineracing.com/dash6.html
I could tap it AN but again, I cant get hold of a tap and it makes getting fittings more difficult.
I could just tap it UNF and seal the thread with an aluminium crush washer...
David
Sera
http://www.motosera.com
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907
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| posted on 8/1/09 at 07:27 PM |
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I'd go with the NPT David.
Paul G
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stuart_g
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| posted on 8/1/09 at 07:27 PM |
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If it is aluminium could you use a threaded insert. I can't remember the exact name for them but they have a course thread on the outside and a
proper thread on the inside.
edit to add: I think they are called a helicoil
[Edited on 8/1/09 by stuart_g]
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flak monkey
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| posted on 8/1/09 at 07:36 PM |
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quote:
Originally posted by 907
I'd go with the NPT David.
Paul G
I would but all the unions I can get are NPTF, not NPT annoyingly. Its my understanding that an male NPTF screwed into a female NPT will not seal,
however it will work the other way round.
Unless anyone has an NPTF tap I can borrow?
Cheers,
David
Sera
http://www.motosera.com
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Alan B
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| posted on 8/1/09 at 07:44 PM |
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David, don't the AN fittings use UNF threads?
quote:
Originally posted by flak monkey
Should perhaps add that it is aluminium fuel rail extrusion, like this:
http://www.rossmachineracing.com/dash6.html
I could tap it AN but again, I cant get hold of a tap and it makes getting fittings more difficult.
I could just tap it UNF and seal the thread with an aluminium crush washer...
David
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Alan B
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| posted on 8/1/09 at 07:50 PM |
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Yes Alan the AN fittings do use UNF threads....
A AN-6 for a 3/8" hose uses a 9/16"-18 (UNF) thread.
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flak monkey
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| posted on 8/1/09 at 08:39 PM |
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quote:
Originally posted by Alan B
Yes Alan the AN fittings do use UNF threads....
A AN-6 for a 3/8" hose uses a 9/16"-18 (UNF) thread.
Sweeeeet 
Looks like thats the way to do it then, and seal it with an o-ring or crush washer
Cheers,
David
Sera
http://www.motosera.com
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martyn_16v
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| posted on 10/1/09 at 11:18 PM |
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I did mine M14 x1.5 as it's tap size is bang on 1/2", and then used a male-male adapter. I think clairetoo found a much easier/cheaper way
to fit 8mm barbed tails to the end of the rail though...
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