In the 1940's Faber-Castell developed the first major variant to the wood cased and propelling types of pencil. The method of operation and lead size each had an influence on the descriptive terms used to name the product which was come to be known as a 2mm Drop Action Clutch Pencil or, more recently, just Clutch Pencil.
The Faber-Castell Product range is named the "TK Range" and the letters stand for the German words "techniker" and "künstler", which mean technician and artist respectively.
In general, the moving parts and the components which respond to pressure are metal. The barrel is plastic. Lead is held in a spring loaded 3-jaw metal clutch which is, in turn, held in a metal clamping ring. The 3 jaws of the clutch have a serrated inner face which increase the hold they have on the lead and prevent slipping.
When the push button is pressed, the jaws advance and, under their own tensile pressure, spring open. They release their grip on the lead. The lead is then free to drop - hence the term "Drop Action" - and it falls under its own weight. The required length of exposed lead must be determined manually.
The TK 9400 Clutch Pencil is 145mm long. It has an hexagonal barrel with round ribbed grip. It has a slender, well-balanced barrel which keeps the center of gravity at the grip section. It is used for technical drawing, writing and sketching.
The pencil accepts TK 9071 2mm leads available in 11 degrees of lead hardness. 3.15mm is available in 3 degrees (6B, 5B, 4B) as special order.
The lead can be sharpened to a variety of shapes and points.
Main specialist uses for grades:
Drafting: 2B B HB F H 2H 3H 4H 5H 6H
Surveying: H 2H 3H 4H 5H 6H
Writing: 2B B HB F H
Drafts, Layouts: 3B 2B B HB F H
Micro Filming: 3B 2B B HB F H 2H 3H
Art & Design: 3B 2B B HB F H