CAD software is used in so many fields of design that it would be impossible to develop extensive standards that apply to all of them. I’ve trained people who use AutoCAD to design quilts, hearing aids, doll clothes, houses, barns, commercial buildings, M16s, submarine hatches, and the myriad components of machinery. But there are some foundational rules that represent a consensus among serious users of CAD. You’ll find exceptions to these rules, of course, but think of them the way you think of the rules for dimensioning drawings: You follow them if possible. The fact that a rule has rare exceptions doesn’t reduce its value as a guide. You certainly follow the rules requiring you to drive on the proper side of the road all the time—except when a dog darts out in front of you, or the road is washed away by a flash flood, or you’re passing someone. So, here are some of my rules for using AutoCAD.

Draw Everything Actual Size

Unless you have a very good reason not to, draw everything at its actual size. Even details can be drawn full size, if you use layouts. They may not look right to you in the Model Space tab,but you can display them in Paper Space viewports and give them any scale you want. At one time, you would have used the SCALE command and then set DIMLFAC to compensate for dimensions, but that’s not a good idea now. You know why. At some point, you’ll forget that your dimension style is multiplying every dimension by 2; or you’ll dimension a detail and forget to change DIMLFAC, and all the dimensions will be half their actual size. You have a complex enough job as it is, keeping track of so many details. Why not simplify your life by drawing everything the size it’s supposed to be? You’re not at a drafting table. Worry about how something will plot when you set up a layout.

I’ve done a lot of training for different industries and have looked for situations where it was impossible to draw full size; I haven’t found an instance yet that couldn’t be addressed using Paper Space. At one shop I worked for, two groups of designers who used AutoCAD had a difference of opinion about full size versus scale. One group of designers thought they couldn’t draw full size because they were designing long pieces with almost no detail along their lengths but a lot of detail at the ends. They only drew the ends, and then they broke the piece with a conventional break and plotted it for the fabricators. The dissenting designers wanted to draw parts at their actual lengths so they could use them in assembly drawings without re-creating them.

The solution I offered was to draw the pieces full length, with proper end detail, and then create a layout with two viewports to represent each end of the object. As long as the two viewports were at the same scale and aligned, they could be separated for a break symbol to be added in Paper Space. Even the dimension of the overall length was correct, because it was in Model Space (where I think it normally ) .

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