# Mathematical / geometric BSP thread

Question asked by Lasse Nielsen on Nov 22, 2018
Latest reply on Nov 22, 2018 by Ruben Balderrama

Hello Forum,

I have been trying to figure out the mathematical / geometric relations for a BSP and Metric. So far i nailed the metric, but the BSP is still bothering me, so maybe someone can help me.

British Standard Pipe - Wikipedia

From this article the pitch is written as decimal number, but the mathematical relation is 25,4/TPI, e.g 2,309 for TPI=11

When searching google for information regarding BSP the taper is for instance often denoted as 1° 47' = 1,78 (rounded). But the mathematical precise relation is a right triangle with height 16 and width 0,5.

When drawing a triangle with base 25,4/11 = 2,309 and angle 55° between the to remaining sides (See image) you get a height which you can calculate.

I found that 4*H/6 times 2 is the precise difference between D Major and D minor from the wiki article.

But then comes the actual diameter. For instance 1" is 33,249 which is very weird number which I cannot, for the love of god, find any reason for.

Can anybody help me figure this out? 