Keep in mind that the softer the lead, B, 2B, etc., the easier it is to smudge the line once it is drawn. For this reason border lines should be the last line drawn on your drafted document.
LINE WEIGHTS FOR LETTERING
The weight of the lines for lettering varies with the size and scale of the drawing and the visual importance of the lettering. Random notes on the drawing and information from leader lines and dimension lines may be a lightweight line to match the line style. Text within a title block may be medium to bold depending upon its importance. Likewise, lettering used to label a drawing such as FLOOR PLAN or SOUTH ELEVATION, may need to be medium or bold as well. Within the range of light, medium, and bold line weights, you may also vary the weights slightly as needed to emphasize a part of the drawing. Typical letting heights are: 3/16”-1/4” for main titles under drawings; 1/8”-3/16” for subtitles and room names; 1/8” for notes and dimensions; and 1/2” for sheet number in the title block.