Technical pen

The Graphos technical pen introduced in 1934 miniaturized the caliper principle and made the points easily interchangeable.

Additionally, in later models, the tube had a small ledge that effectively narrowed its end, that—while maintaining the line thickness—made the tube thicker along most of its length and also protected ink from spilling while drawing along the edge of a rule, set-square, T-square or other template (the ink had no immediate contact with the template's edge).

In the United States, several firms produced this kind of technical pen: WRICO, Leroy, and Koh-I-Noor.

Some other brands that manufacture technical pens not following ISO standards are Faber-Castell, Isomars, Alvin, Hero, and Standardgraph.

A full set of pens would have the following nib sizes: 0.10, 0.13, 0.18, 0.25, 0.35, 0.50, 0.70, 1.0, 1.4, and 2.0 mm, which correspond to the line widths as defined in ISO 128.

This worldwide standard (excepting Canada and the United States) ensures that drawings can always be legible even after microfilming, photocopying, and faxing.

Brushing charged the surface, and the film would then be taped taut (but released at the end of each working day to allow for overnight temperature expansions and contractions).

These had the basic characteristics of the standard pen nib, but the tube was much thicker to strengthen it against quick lateral movements.

While the Rapidograph style of pen is still widely used by artists, the use of computer-aided design (CAD) has largely replaced the need for manual drafting.