[ROVERNET - UK] P6B nuts and bolts specs

Warwick Brooks warwick at regscom.com.au
Tue Nov 6 02:15:34 GMT 2007


BSP is the British Standard Pipe thread and comes in 2 types.

BSPT:  Tapered thread – used to provide a self-sealing joint between pipes
and fittings.  Because of the taper (which is visible), the joint gets
tighter and tighter as the parts are screwed together until they eventually
jam.

BSPP:  Parallel thread which will just keep screwing together until you run
out of thread.

BSP was adopted into the metric system as the pipe thread but with the size
being given in millimetres.

The US standard is NPT (National Pipe Thread) and from ½” size down the
difference between BSP and NTP is slight and a tapered thread can usually be
used interchangeably without damage.  This is particularly the case for
3/8”, ¼” and 1/8”.

Pipe tends to have heavier wall thickness and is joined by cutting a thread
on the outside and screwing together, or butt-welding.

Pipe size is determined by the bore of the pipe.  A ½” pipe has a ½” hole
down the middle.

Pipe fittings sizes are determined by the size of pipe that will screw into
them.
A ½” pipe elbow has a threaded hole large enough to take a ½” pipe, so the
hole is a lot bigger than ½”.

Tube tends to have a thinner wall and is joined by slipping it inside a
fitting that squeezed in on it to seal using ferrules or O-rings, etc., or
it is brazed or soldered into the fitting.  It may also be flared at the end
and used in a fitting that squeezes the flared end against a nipple of
similar profile.

Tube sizes are determined by outside diameter.

A ½” tube will fit neatly into a ½” hole while the hole down the centre of
the tube is less than ½” by the thickness of the wall.

Tube fittings sizes are also determined by the size of the tube that they
accept and so a ½” tube elbow has a ½” hole.

Hoses are hose pipes and so are measured by the inside diameter or bore.
Plastic tubing is tube and is measured by its OD.

This is why a ½” steel water pipe is so much bigger that a ½” copper tube.

Plumbing fittings associated with engines, such as pressure and temperature
fittings that screw into the block will generally be BSP or NPT and so if
they are ½” or less they will be interchangeable without damage.  (1/2”
being the borderline size).


Warwick.

-----Original Message-----
From: rovernet-bounces at lyris.ccdata.com
[mailto:rovernet-bounces at lyris.ccdata.com] On Behalf Of Warwick Brooks
Sent: Tuesday, 6 November 2007 12:37 PM
To: rovernet at lyris.ccdata.com
Subject: RE: [ROVERNET - UK] P6B nuts and bolts specs

Just thought I would add this bit of info that may not be apparent to all,
regarding BSW (Whitworth) and SAE (AF).  That being that SAE is the standard
(Society of Automotive Engineers) while AF simply means Across the Flats and
refers to the size of the bolt-head when measured from one side of the
hexagonal head to the other, across the flats.

Therefore a 1/2" SAE bolt-head is 1/2" across and the corresponding spanner
is 1/2" plus clearance between the jaws.  Metric sizes are also measured
across the flats so a 12mm spanner fits a 12mm head.

Whitworth or British Standard Whitworth sizes are based on the shank size of
the bolt, not the head.  So a 1/2" BSW bolt fits a 1/2" hole (plus
clearance) and so the head is much bigger across the flats.

This is why an SAE 1" spanner is marked 1" AF and is a reasonably large
spanner, while a 1" Whitworth spanner is marked 1" BSW and is a bloody big
spanner.

Now having just gone to the trouble of writing this it occurred to me that
somewhere on the web, someone may have done a better job of it, so I looked,
and they had, and it was.

So here it is...

http://www.internationalcockpitclub.org.uk/articles/article_threads.htm

Regards,
Warwick. 

-----Original Message-----
From: rovernet-bounces at lyris.ccdata.com
[mailto:rovernet-bounces at lyris.ccdata.com] On Behalf Of Brooks
Sent: Monday, 5 November 2007 11:33 AM
To: rovernet at lyris.ccdata.com
Subject: Re: [ROVERNET - UK] P6B nuts and bolts specs

 Thank you ...that was extremely informative and appreciated.

Regards

 Dennis


----- Original Message ----- 
From: "Aidrian Bridgeman-Sutton" <smokeandsteam at gmail.com>
To: <rovernet at lyris.ccdata.com>
Sent: Sunday, November 04, 2007 8:12 PM
Subject: Re: [ROVERNET - UK] P6B nuts and bolts specs


> On 11/3/07, Brooks <restore at nbnet.nb.ca> wrote:
>> "the car is UNF and UNC
>> throughout."
>>
>>  I'm sorry...but I don't know what these terms represent...
>
> "Unified National Fine" and "Unified National Coarse" which were
> originally specified in the 19th century and eventually became US
> standards. You will also see them referred to as SAE threads. Your
> standard toolkit will fit
>
> SAE/Unified threads began to  become more widespread among British
> makers in the 50s into the 70s until metrication; the "Unified" part
> of the name comes from an agreement among various standards bodies in
> the late forties to ensure at lest some commonality between the
> various inch-based countries in NATO.
>
> Carbs, electrical parts and instruments were often held together with
> BA (British Association) screws; BA is a long established thread form
> used in instrumentation and is based on a metric measurements, but is
> not compatible with the ISO metric system except by accident.
>
> While technically obsolete  BA hardware and tools are still available
> as BA screws are much favoured by model railway enthusiasts in the
> Commonwealth countries
>
> Having said that there is one other thread standard you need to be
> aware of, BSP which is sonetimes used for things like temperatore
> sensors and which can trip up the unwary.
>
> Aidrian
>
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