Tierlieb

August 13, 2010, 01:03 PM

Hello there,

I'm looking for the dimensions on MIL-STD 1913 rails. I know where to get the official paper. Wikipedia has a nice scalable SVG version of the first of two figures:

http://upload.wikimedia.org/wikipedia/commons/thumb/6/6a/M1913A_Rail_CrossSection.svg/500px-M1913A_Rail_CrossSection.svg.png (http://upload.wikimedia.org/wikipedia/commons/6/6a/M1913A_Rail_CrossSection.svg)

But I cannot figure how to read it. Well, I can read the width of the base (.617), I get the angle (45°), I know the heights of the whole block (.367). I figure the width of the diamond shaped block is .835 at its broadest, although I wonder why the lines are drawn like they do exclude the outermost points. Especially since the real rails I measured (from Samson Mfg) differ a bit from those. But I can't seem to figure out how high the diamond-shaped block is - or maybe the top half of that. Why are all those measurements taken from the middle of lines, not their endpoints?

I thought before I enlarge the original, print it out and use the known measurements to deduce the rest by cross-multiplication, I'd ask here if someone can point me in the right direction. This has to be easy. Trained engineers probably can read it.

I'm looking for the dimensions on MIL-STD 1913 rails. I know where to get the official paper. Wikipedia has a nice scalable SVG version of the first of two figures:

http://upload.wikimedia.org/wikipedia/commons/thumb/6/6a/M1913A_Rail_CrossSection.svg/500px-M1913A_Rail_CrossSection.svg.png (http://upload.wikimedia.org/wikipedia/commons/6/6a/M1913A_Rail_CrossSection.svg)

But I cannot figure how to read it. Well, I can read the width of the base (.617), I get the angle (45°), I know the heights of the whole block (.367). I figure the width of the diamond shaped block is .835 at its broadest, although I wonder why the lines are drawn like they do exclude the outermost points. Especially since the real rails I measured (from Samson Mfg) differ a bit from those. But I can't seem to figure out how high the diamond-shaped block is - or maybe the top half of that. Why are all those measurements taken from the middle of lines, not their endpoints?

I thought before I enlarge the original, print it out and use the known measurements to deduce the rest by cross-multiplication, I'd ask here if someone can point me in the right direction. This has to be easy. Trained engineers probably can read it.