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joeybaby83

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Isle of Man

26th Sep, 2006 at 05:42:40pm

Need to drill and tap a hole for 1/4 bsp and got a couple of questions.

1) What should i drill the initial hole out to?

2) If the union Im using has a 1/4 bsp thread, but is tapered do i need a specific tap, or will a parallel one be ok?

Cheers guys, I cant find my engineers book..

Jo

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Paul S

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26th Sep, 2006 at 06:01:20pm


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joeybaby83

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Isle of Man

26th Sep, 2006 at 06:05:42pm

great site, but.....no info on bsp or npt...

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Tom Fenton
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26th Sep, 2006 at 06:23:21pm

Size is 7/16" or 11.2mm from what I can remember, however if you are tapping into alloy castings (gearbox oil temp sender? or a pipe nipple into the inlet manifold?) it is worth using a slightly smaller drill to leave a shade more material to bite into. I have used 11.0mm with no problems at all.

You will be fine with a parallel thread, just make sure you have a reasonably flat face to use a dowty washer or similar to seal your connection. Also a touch of PTFE tape as well.


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joeybaby83

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Isle of Man

26th Sep, 2006 at 06:24:53pm

11.8mm

www.rwc.yertiz.com/tapchart.pdf

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joeybaby83

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Isle of Man

26th Sep, 2006 at 06:28:12pm

cheers tom, must have posted while i was copy/pasting.

Ill try 11mm to start with as better safe than sorry :)

Its for an oil take off from the block, using a remote oil filter for more space up front.

cheers guys

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"



wil_h

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Betwix Harrogate and York

26th Sep, 2006 at 08:08:09pm

On 26/09/2006 17:42:40 joeybaby83 said:
2) If the union Im using has a 1/4 bsp thread, but is tapered do i need a specific tap, or will a parallel one be ok?



I can't find my Zeus book either, but I seem to think that only the male part is tapered.

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the design shows a distinct lack of imagination,
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I'm mainly concerned about swirl in the runners caused by the tangential entry.


antman

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26th Sep, 2006 at 08:33:00pm

You do need a special tap for a BSP taper in order to get the seal nice. I have used a normal bsp tap with a tapered fitting and with plenty of hydraulic thread lock and winding the fitting in well it has yet to leak!! The drilling size for 1/4 bsp is 11.8mm and the BSP taper is 11.2mm for the nominal sizes but depnding on the material alter accordingly.
Anthony
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