Quote:
Originally Posted by jplinville
My definition of "Mechanical Feel" translates to my trade as this...
Detail drawings in ACAD are generally done in a "3 view drawing", meaning 3 sides of the part are shown, so someone is able to machine the part and make it to print.
A "Datum" is a point on the part, usually a corner, where dimensions generate.
Someone who has no "Mechanical Feel", or mechanical experience will use multiple datums to dimension from for each view...meaning they will have some features dimensioned from the left side, some from the right side, some from the tip and some from the bottom. When this is done, it creates more work for the person machining the part, because they have to re-dimension the part to make it easier to machine.
Therefore, when someone lacks the "Mechanical Feel" they lack the experience to properly draw a part. They may be able to draw, but they cannot draw it in such a way that it can be made properly.
I hope that's clear as mud.  |
I see your point as far as what you consider a datum. On ASME drawings you genrally have three datums, for Geometric Dimensioning and Toleranceing. Basically, you are dealing with a three dimensional or Cartesian cordinate system. So, usually two or three datums are needed. 'A' is usually the base, "B" locates in the 'X' plane or a hole and 'C' clocks the part or keep it from rotation. Mating surfaces usually have another datum. Usually, your dimensions come from 'B' or 'A'. On some parts, dimensions will be from another datum or feature. That signifies or keeps say bolt holes related to that feature. A good example would be bolt holes for a starter boss on a flywheel housing
Tom