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be correct, and 45cm would be incorrect. Check your own office standards before you incorporate this feature, which you can find on the Primary Units tab of the New/Modify Dimension Style dialog box.

Other style settings

If your work requires that you show dimensions in two different systems of measure (such as inches and millimeters), use the Alternate Units tab to turn on and control alternate units. Alternate Units display both dimensions at once.

If your work requires listing construction or manufacturing tolerances (for example, 3.5 +/–0.01), use the Tolerances tab to configure the tolerance format that you want.

AutoCAD also includes a separate TOLERANCE command that draws special symbols called geometric tolerances. If you need these symbols, you probably know it (and you have our sympathies); if you’ve never heard of them, just ignore them. Look up Geometric Tolerance dialog box in the AutoCAD help system for more information.

Size Matters

As discussed in Chapter 13, Chapter 15, and earlier in this chapter, the size of text and dimensions applied in model space has to be adjusted to suit the final plotting scale of the drawing. As we repeat several times in several chapters, by far the best way of doing this is to use annotative dimensions. To see what we mean, try this:

1.Start a new, blank imperial drawing.

Use the acad.dwt template.

2.Draw a horizontal line about 20 units long.

3.Apply a linear dimension (DimLin, or DLI) to the line.

Pretty hard to read, isn’t it?

4.Switch to the Annotative dimension style.

Find the window in the upper-right corner of the Dimension panel of the Annotate tab of the Ribbon that reads Standard. Click it and then choose Annotative from the drop-down list.

5.Change the drawing scale.

Select the 1:5 scale from the drop-down list under the Annotation Scale button in the lower-right corner of the drawing window.

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316 Part III: If Drawings Could Talk

6.Dimension the line again.

Ah, that’s better, and it didn’t require any esoteric calculations.

To avoid confusing results, which is what has turned most users off from using annotative annotations, make sure that the Automatically Add Scales button in the lower-right corner is turned off. We discuss this more in Chapter 13.

Details at other scales

Dimensioning details at different scales was always the hardest type of dimensioning, and still is unless you use annotative dimensions.

The hard way

We used to draw the complete object full-size, including all the fine details, zooming in as necessary. Next, we would copy those elements that made up the fine detail and then use the SCALE command to resize them to suit the detail scale. Finally, we would apply dimensions to the scaled one that had two suitable scale factors: First, we had to set the dimension scale factor to suit the overall drawing scale (say 1:2), and then we had to set the DIMLFAC (DIMension Linear FACtor) to suit the detail scale.

The problem is that we have been telling you all along to draw “full size” so that dimensions automatically measure the object to which they are applied, but now our detail is at a different scale. DIMLFAC is a fudge factor applied to dimensions that corrects the measured value, so a 1" line in a 5:1 detail will measure as 1 inch, not 5 inches. Ouch. And we haven’t even gone into all the gruesome details about how to calculate all those scale factors, and heaven help you should you need to edit the main view or the detail. Again, we mention the hard way only because a lot of existing drawings are lurking out there.

The easy way

Here’s the easy way to create a multiscale drawing, such as the one in Figure 14-5.

1.Draw the object full-size in model space, including the small notch detail.

2.Select the 1:10 scale from the drop-down list under the Annotation Scale button in the lower-right corner of the AutoCAD window.

3.Apply the three dimensions that show in the Scale 1:10 view in Figure 14-5, using an annotative dimension style.

The figure shows paper space, but you’re working in model space.

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Chapter 14: Entering New Dimensions 317

Figure 14-5: A drawing with a detail at another scale.

4.Apply an annotative hatch, as we discuss in Chapter 15, and then draw the center line.

5.Edit the properties of the hatch pattern and the 1.400 dimension to add 1:2 scale factors, as we describe in Chapter 13.

6.Make sure that the Automatically Add Annotative Scales button is turned off, and change the Annotation Scale to 1:2.

Three existing dimensions disappear, and the hatch and the 1.400 dimension resize themselves.

7.Add the 1.500 and 2.400 dimensions.

8.Now comes the magic part. Switch to the paper space Layout 1 tab. Click the viewport boundary and then grip edit it approximately to the size and location shown.

Your model space drawing is probably not properly located, and the hatch and dimensions won’t show.

9.Click the viewport boundary again, and then click the Viewport Scale button (it probably reads something like 0.694694) and select 1:10 from the scale list.

The viewport zooms accordingly, and the hatch and 1:10 dimensions appear. If necessary, double-click in the viewport to enter model space and then pan accordingly.

Don’t zoom, or you lose the scale setting!

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