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Rifles, Reloading, Optics, Equipment
Long Range Scopes and Other Optics
Picatinny Rails?
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<blockquote data-quote="westcliffe01" data-source="post: 860737" data-attributes="member: 35183"><p>Ok, I am not a professional cad jocky but I am an engineer and do about 90% of my own CAD work except for loading them in SAP.</p><p></p><p>I'm trying to understand your issue with drawing this section.</p><p></p><p>If we assume that the 0.748 dimension is the "gauge" distance for the dovetail and that the 0.108 gauge height is centered on the 90 degree corner, then working outwards the dimension to the theoretical corner intersection is 0.748 + 2x(0.108/2) = 0.856. </p><p></p><p>So the fact that the print shows a dimension (which appears to be corner to corner) of 0.835" suggests that the rail does not have a sharp corner but in fact has a small flat which is (0.0105^2*2)^0.5*2 = 0.0297" wide (vertically).</p><p></p><p>If you think about it, it is never good engineering practice to put a sharp corner on something which is going to fit into an outer part. That is because no-one can make a tool that cuts a true square corner (at least not for very long). So cutting tools have a radius on the edge and the part that fits into the feature needs a flat or chamfer to clear the radius so that it can be properly seated on the 2 45 degree faces as intended.</p><p></p><p>I was going to write you a description of how to draw it, but I don't think you need it now ? All clear ?</p><p></p><p>I will add that a good print would show a detail of that corner feature so you could see the 0.030" flat, but this was probably done a long time ago and they were probably initially cut by artisans who understood how things needed to be made to fit together and not by operators hired off the street who were shown where to push the button.</p><p></p><p>I will tell you that the hardest thing one ever has to accomplish as an engineer is to get artisans to trust your work. The problem being that the work they get from about 90% of the engineers is incapable of fitting together and the shop gets blamed for delays at the end when it does not go together... The day that guys from the shop floor walk in your door with suggestions about how to make your work better (instead of *** is this sh&$%t ?) you have "arrived".</p></blockquote><p></p>
[QUOTE="westcliffe01, post: 860737, member: 35183"] Ok, I am not a professional cad jocky but I am an engineer and do about 90% of my own CAD work except for loading them in SAP. I'm trying to understand your issue with drawing this section. If we assume that the 0.748 dimension is the "gauge" distance for the dovetail and that the 0.108 gauge height is centered on the 90 degree corner, then working outwards the dimension to the theoretical corner intersection is 0.748 + 2x(0.108/2) = 0.856. So the fact that the print shows a dimension (which appears to be corner to corner) of 0.835" suggests that the rail does not have a sharp corner but in fact has a small flat which is (0.0105^2*2)^0.5*2 = 0.0297" wide (vertically). If you think about it, it is never good engineering practice to put a sharp corner on something which is going to fit into an outer part. That is because no-one can make a tool that cuts a true square corner (at least not for very long). So cutting tools have a radius on the edge and the part that fits into the feature needs a flat or chamfer to clear the radius so that it can be properly seated on the 2 45 degree faces as intended. I was going to write you a description of how to draw it, but I don't think you need it now ? All clear ? I will add that a good print would show a detail of that corner feature so you could see the 0.030" flat, but this was probably done a long time ago and they were probably initially cut by artisans who understood how things needed to be made to fit together and not by operators hired off the street who were shown where to push the button. I will tell you that the hardest thing one ever has to accomplish as an engineer is to get artisans to trust your work. The problem being that the work they get from about 90% of the engineers is incapable of fitting together and the shop gets blamed for delays at the end when it does not go together... The day that guys from the shop floor walk in your door with suggestions about how to make your work better (instead of *** is this sh&$%t ?) you have "arrived". [/QUOTE]
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