Quote Originally Posted by guest View Post
I have just finished a major search in all things BSP related. Here's the short of it.



BSP British Standard Pipe

This comes in taper and parallel. The jargon varies on how to describe the tap. Most common is the BSPT or BSPP but I have seen BSP be parallel.

Then we get into all the variations

G, how I’ve come to hate this letter. This means Gas, which means… about anything. Most common is a reference to a BSW ( I haven’t introduced this one yet) or a parallel thread.

So now BSW similar to the rest but the W is for whitworth. This seems to have the most association with ‘G’, though I have seen it referenced as something other than the BS family

This reference is pretty good and seems to be accurate.

http://en.wikipedia.org/wiki/British...rd_pipe_thread

So what you have is a BSPP(‘L’ is sometimes here) whitworth 55 degree thread. There is also a full form and modified form. The full form is from Europe and couldn’t be made in the US and so the US made a modified. Now everyone can make it and so… good luck with that but it shouldn’t make a lot of difference. Has to do with a radius on the minor axis.

As for getting one… prepare thyself…..

This link has some for a very good price. I myself need a 1/8 G, but these are like 220 V 50 Hz. Uncommon here and so expensive.

http://www.blujay.com/item/NEW-4-PCS...060000-1738603

McMaster Carr has some if you use BSPP in the search. It doesn’t say if it is whitworth or full or modified. There may be other places as well. If you search for BSPP and look for a ¼ you should be ok but remember that the jargon can confuse what you’re getting. It will likely take a call to confirm.
I (or C'DaleRider or any other machinist) could have saved you a lot of work if you had asked. BSP is also usually followed by a letter designation to specify exactly which BSP should be made. You forgot another common letter as well. "R" designates a tapered (otherwise known as a BSPT) thread. As stated in the Wiki, all BSP threads are based on the Whitworth thread.

Here's some more on BSP threads straight from the Machinery's Handbook 26th Edition which is more or less the Bible for anyone in design or manufacturing.



Also, BSPP (G) seals with O-Rings (teflon tape or pipe dope is nearly useless on these), BSPT (R) seals with Teflon tape (or pipe dope). It's best not to mix the two types of threads as you'll only have only a few threads grabbing which ever way you mix, thereby increasing your risk of a leak.



Quote Originally Posted by Martinm210 View Post
FYI
I ordered the BSPP tap from Master Carr and it turned out to be the bottomless variety. I also picked up an 11.8mm drill bit to go with it.

They are both very nice and worth the money, but you probably would want a tapered cut tap if you're hand tapping.

I like the bottomless because I'm tapping in my mill, but it would probably be a PITA to keep a nice perpenticular tap by hand.

The 11.8mm drill bit also works wonders by removing just the right amount of material. I'm literally able to hand tap in plastics by hand turning my chuck without any wrench and threads are perfect every time. I was not able to do that with the NPT-18 tap, and threads were never perfect either.

Anyhow, I'm glad it is bottomless, but something to watch for if you're ordering from Mcmaster-carr...
Bottomless?

Sorry, couldn't help myself.

It seems it's been a very long time since you were on the floor of a shop. The styles of taps available are Bottoming, Plug, and Tapered. With a BSPP or NPSM, the only style tap available is a bottoming as there can't be any taper otherwise it's not a BSPP or NPSM.