Dimension Scale and Mixed Tolerances on a Fabrication Package
A machine shop detailer is producing a 12-sheet fabrication package for a stainless steel bracket assembly. Model-space geometry is drawn at 1:1 in millimeters. Details are shown in viewports at 1:2, 1:5, and 1:10. The dimension style FAB-ISO uses text height 2.5 mm, arrow size 2.5 mm, and DIMSCALE 1; it is not annotative. Dimensions in the 1:10 viewport appear tiny, so a drafter changes DIMSCALE to 10. Now the 1:2 viewport dimensions are huge. A tolerance note requires plus or minus 0.2 mm for hole diameters and plus or minus 0.5 mm for overall lengths; the drafter uses a single dimension style with a symmetric 0.5 mm tolerance for all dimensions. The inspector rejects the drawing because hole tolerances are wrong. The team also needs dual units, mm primary and inch secondary, for an overseas client.
1. Explain the cause of the dimension size inconsistency and recommend a dimension style strategy for the three viewport scales.
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The inconsistency is caused by using one non-annotative dimension style with a fixed DIMSCALE. A model-space dimension is one object; if it appears in a 1:2 and a 1:10 viewport, no single DIMSCALE can make its text 2.5 mm in both. Changing DIMSCALE to 10 fixes 1:10 and breaks 1:2. Use an annotative dimension style: set the style annotative, add 1:2, 1:5, and 1:10 to the scale list, and assign the appropriate annotation scale to each dimension. Alternatively, use separate non-annotative styles with DIMSCALE 2, 5, and 10 on separate layers, but that duplicates dimensions. Verify the plotted text height with a PDF at each viewport scale.
2. How should tolerances be assigned so hole diameters and overall lengths carry different values without duplicating geometry?
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Create child styles or per-dimension overrides: FAB-HOLE with DIMTOL on, DIMTP 0.2, and DIMTM 0.2; FAB-LENGTH with DIMTP 0.5 and DIMTM 0.5. Apply the hole style to diameter dimensions and the length style to overall dimensions. Do not use a text override, because it breaks associativity and is easy to miss. Check that the tolerance values display with the correct number of decimal places and that the dimension text does not overlap at 1:2. Run a dimension audit by filtering diameter dimensions and comparing their style in Properties.
3. What steps are needed to add dual mm and inch units and verify the dimensions will plot correctly at 1:5?
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In the dimension style, enable alternate units: DIMALT=1, DIMALTF=0.0393701, DIMALTD=3 or 4, DIMALTU=2, and set a suffix such as in if required. Keep millimeters primary and verify that the alternate value is rounded consistently. For the 1:5 viewport, confirm the dimension is annotative at 1:5, text height is 2.5 mm at plot scale, and arrow size is 2.5 mm. Plot a test PDF and measure a known 50 mm dimension; check that dual units and tolerances both appear without exceeding the available space.