Picatinny dimensions / MIL_STD-1913


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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.

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rcmodel
August 13, 2010, 01:36 PM
although I wonder why the lines are drawn like they do exclude the outermost points..835" - .005" is the outside point of the diamonds.

.748" - .002" is the outside of the recoil groove cuts.

Why are all those measurements taken from the middle of lines, not their endpoints?I believe those measurements are taken to datum points on the angles.
The actual hight of the diamond isn't important as long as the datum points are exact so the clamps will clamp tight on them at that location.

I think.

rc

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