Have you ever wondered how a "lead" pencil is made? Well, wonder no more.
First of all, there's no "lead" in a lead pencil. The main ingredient is graphite. When the graphite was first mined (in the 1500s in England), it had a similar look to lead and was referred too as "dark lead". As the technology evolved to allow testing of minerals, it was subsequently discovered to be an entirely different material.
Early pencils were just a stick of graphite wrapped in string, but the graphite was very brittle and needed a better holder, so a hollowed out piece of wood was then used. In 1662, the Germans are credited with developing the first mass produced pencils, after being the first recorded to make graphite sticks with powdered graphite. The technique used then to cut the timber for pencil manufacture is very much the same today, although the development of the "lead" itself continued for longer, and was patented in 1804 in Austria.
The central filling of a graphite pencil is a mix of graphite and clay, ground to a fine powder and mixed with water. This combination has been used since the 17th century. The wet mix is blended over a few days, then drained and air-dried, then reground and wet again, before being extruded into thin tubes, cut to length and fired.
The wood is cut into thin, flat slabs, about 8 pencils wide and half a pencil thick. A series of grooves are cut into the timber to fit the leads. The leads are glued into the grooves and a matching slab is glued over the top in a tight sandwich.
A machine trims the slabs around the pencils, then cuts them apart. The individual pencils are then sanded and painted with 5-8 coats of lacquer and then they can be stamped with the company name and any details including the pencil's grading number and have any other decorations applied, such as prints or films. A metal band, known as a ferrule can be added at this point which will clamp the eraser in place, if that is being used.
Graphite pencils often carry a a grading code called the HB graphite scale. H stands for Hardness and B for blackness.
Harder pencils contain more clay and deposit less material on the paper, leaving a lighter mark. Conversely, higher amounts of graphite create a softer pencil which leaves more material behind and a blacker, darker result. Artists will usually use a combination of pencils in a graphite drawing to make use of the different types of marks they make. Standard office pencils are usually the central HB. I personally prefer a 2B for both writing and general sketching.
If you want to see the process in photos, this old-school American company does it very well here: https://www.generalpencil.com/how-a-pencil-is-made.html
If you want to see a video of the process, here is one from The Insider: https://youtu.be/qqs3fxfmWr4