Oh... so 1/4" BSP is 1/2" across, then...!

[skotl]

Had a moment today... I needed to order an air filter/regulator and an assortment of adapters and stopped short when I saw some described as being 1/2" rather than the 1/4" I swore I ordered previously.

Tromped out to the garage to measure what I've got and they all came out as just over 1/2" or ~13mm.

Back indoors to the computer to stare at the images on google... all these 1/4" connectors definitely look like what I have, so what gives?

Until I finally cottoned on that just because something is referred to as an apple, it does not mean that it is actually an apple. So 1/4 BSP is actually just over 1/2" across - right, gotcha

For anyone else as slow as me; http://en.wikipedia.org/wiki/British_Standard_Pipe

 

[normspanners]

I have used 1/2 unf tap and 'wobbled' it a little to tapercut the thread and threaded a 1/4 bsp fitting into when needed because i didnt have 1/4 bsp tap
the unf is 20 tpi and bsp is 19

 

[Bsmith]

British Standard Pipe sizes refer to the hole through the pipe size, even that is usually way out if you measure it.

 

[skotl]

British Standard Pipe sizes refer to the hole through the pipe size, even that is usually way out if you measure it.

I kinda surmised that, but then the tables at http://en.wikipedia.org/wiki/British_Standard_Pipe and else where don't seem to support that theory, either. The corresponding pipe diameter for 1/4" BSP is .53"

Still - the important point (for me, anyway ) is that when I look at a fitting that's around a 1/2" then I know it's 1/4" BSP - simples

 

[normspanners]

Your gettin muckin fuddled

The corresponding pipe diameter for 1/4" BSP is .53"

Yes thats the OD not the bore or inside of the pipe which is 1/4" (on thick wall stuff)

British Standard Pipe sizes refer to the hole through the pipe size,

 

[skotl]

Your gettin muckin fuddled

Yes thats the OD not the bore or inside of the pipe which is 1/4" (on thick wall stuff)

Cheers Norm

Yes - I am getting fuddled! I have spent ~8 months buying 1/4" BSP bits and it was only tonight that I thought "....waaaiiiittttt a minit - they're nae 1/4" across!"
But I'm good now

 

[normspanners]

Also the other way when I have needed a 1/4 bsp boss I have used a standard 1/2 unf nut welded it onto a tank and run a 1/4 bsp tap into it.

 

[J.B. Welding]

Skotl, have you ever come across a Whitworth spanner? Now that is a crazy system!

Look out for JIC fittings too,(actually a real UNC thread) the cones are the other way around than with BSP and they are just slightly different sizes. Mostly used in hydraulics but you never know!!

 

[normspanners]

actually a real UNC thread

not nit pickin but they are unf and they also go in - dash sizes to confuse even further

AN sizes range from -2 (dash two) to -32 in irregular steps, with each step equating to the OD (outside diameter) of the tubing in 1/16" increments. Therefore, a -8 AN size would be equal to 1/2" OD tube (8 x 1/16 = 1/2).

 

[skotl]

You can see why I was confused

 

[J.B. Welding]

Is it not the case that 1/2" JIC is the same size and thread as a 5/8" UNC bolt?

 

[normspanners]

I used to work on poclain cranes and they dont follow any pattern they use bsp metric metric fine one pipe on the clutch was a ridicules price from poclain like £100 and I was trying to sort it during christmas break turns out they had used BSF !! I spent ages measuring it and they nearly foxed me, but i had the dies and made two adapters up a piece of standard goodridge and it was sorted for £10 .

 

[normspanners]

Is it not the case that 1/2" JIC is the same size and thread as a 5/8" UNC bolt?

no

Commonly referred to as just JIC fittings these metal to metal sealing type fittings have a 37° flare (sealing surface angle) and straight United National Fine straight Threads (UNF). The original design specification for the fittings comes from the Society of Automotive Engineers (SAE) and these fittings are the most common American fitting type in Europe.
MALE: The measurements for the male are taken from the outside of the threads.
FEMALE: For the Female, the measurement is taken from the inside of the threads.
The below diagram shows both where to take measurements from and the size dimensions.

 

[J.B. Welding]

Very interesting. I mostly work with BSP and metric fittings, but when confronted with a JIC dilemma I head to my local hydraulics guy who is a proper old school type, really knowledgeable. It seems he's also prone to a bit of standard deviation due to what have ye. BUT, I'm sure (yikes) I can state the advantage of this fitting over BSP.

 

[J.B. Welding]

With BSP the male fitting with the inverted cone can become oversized due to repeated tightening/over-tightening and removal, leading to difficulty in the ability to get the female part on-potentially causing a crossed thread situation. That's why it's important not to over-tighten these things in the first place. As the cones on JIC fittings are the other way around this type of situation is avoided.

 

[rtbcomp]

Just to add to the confusion - 1/2" copper central heating pipes are 1/2" bore, 15mm copper CH pipes are 15mm OD. This is why you can use 15mm solder fittings on 1/2" pipe.

 

[piman]

Hello J.B. Welding,

"Now that is a crazy system!"

Not at all, it's perfectly logical, it refers to the fastener diameter. What confused it was when the war came along and head sizes were reduced . As originally devised it was simple.

Alec

 

[J.B. Welding]

Hello J.B. Welding,

"Now that is a crazy system!"

Not at all, it's perfectly logical, it refers to the fastener diameter. What confused it was when the war came along and head sizes were reduced . As originally devised it was simple.

Alec

Yes true it does refer to the fastener diameter! So a spanner saying 1/2" and actually being way bigger than 1/2" would appear, by post war standards, to be insane!

 

[rtbcomp]

What could be simpler than choosing a spanner marked 1/2" BSW to tighten a 1/2" BSW nut?

It's the current system of labelling spanners with the AF (Across Flats) dimension that's confusing, you have to remember that a 13mm spanner is needed for an 8mm bolt &c.

 

[piman]

Hello Rtbcomp,

but there are anomalies with that also particularly with cheap bolts used in various products where 8mm diameter needs a 14mm spanner, for instance.
All the fasteners I used when doing my apprenticeship were Whitworth and I found it very easy. Part of my time was served in Lancashire and I found that they didn't use ring spanners but ring keys.

Alec