Named dimensions A, B, C and a dimension table on your drawing

Many part drawings do not write numbers on the dimensions at all. They use letters — A, B, C — and a table beside the drawing says A = 22.1 MAX, B = 12.5 ± 0.3. You see this a lot on spec drawings for electronic components, coils, transformers and inspection drawings. DXCAD2D Online names dimensions for you and builds a dimension table that keeps itself up to date.

Why letters instead of numbers?

• One drawing, many sizes. Parts with the same shape in different sizes — five coil variants, say — share one picture; only the table changes.
• Easier QC. Inspection records refer to the same letters as the drawing, with no need to describe where each measurement is.
• A cleaner drawing. Long tolerances such as 12.50 +0.10/−0.05 go in the table instead of crowding the picture.
• Matches customer specs. Many customers already send specs as an A–F table; a drawing in the same form is quicker to check.

Steps in DXCAD2D Online

1. Open DXCAD2D Online, draw the part and dimension it as usual with D (press Tab while placing to switch between horizontal, vertical and aligned).
2. Select the dimensions to name in the order you want them to become A, B, C — click the first, then Shift+click the next.
3. In the properties panel on the right, click Name A, B, C… in the order picked. The dimensions now show letters instead of values.
4. Click Insert / update the dimension table. The table appears beside the drawing: UNIT : mm on the first line, then A = … in letter order.
5. Move the table where you want it with M.

Tolerances and table values

Select one dimension at a time and the panel shows these fields:

The table updates by itself whenever you change a name, value or tolerance, or stretch the part so a measured value changes — there is no need to rebuild it. To go back to numbers on a dimension, select it and click Clear names (show values).

Naming conventions used in practice

• Order the letters the way people read: left to right, top to bottom, or overall sizes before detail sizes.
• Avoid letters easily confused with digits, such as I and O, where you can. Automatic naming goes in sequence; rename afterwards if needed.
• Use MAX or MIN for sizes that only matter in one direction, such as an overall height that must fit a mounting space.
• Always state the unit. The generated table starts with UNIT : mm.
• If one picture serves several variants, make a table per variant (or a multi-column table with text) and note in the title block that the picture is not to scale.

Frequently asked questions

Why do drawings use letters A, B, C instead of numbers

So one picture serves several sizes, QC can refer to the same measurement points, the drawing stays uncluttered because long tolerances live in the table, and it matches customer specs that already come as an A–F table.

Does the dimension table update automatically

Yes. It updates whenever you change a name, a table value or a tolerance, or stretch the part so a measured value changes — no need to rebuild it.

Can I type a table value when the picture is not to scale

Yes. Fill in the "value in the table" field and the table uses it instead of the measured value — handy for a sketch shared by several variants.

What kind of work are named dimensions best for

Spec drawings for electronic components, coils and transformers, and inspection drawings where QC records results against named points.

For dimensioning basics, see ISO dimensioning basics.