That's right. The history was interesting - from wonderful pure mined lead to that becoming shorter in supply and two individuals at the same time realizing they could add clay to the lead, fire it and then I don't know if they did or someone else did later, soak the fired leads in wax to achieve smoothness while writing.
the blackwing pencils are enormously expensive, but there is a feel to them that no drafting lead has. If you're making the pencil, some part of the lead channel is glue, so the leads don't have to be perfect - and they weren't in original pencils.
I did find out why pencils aren't octagonal when I started making them - the way we grip them, if they are hexagonal, the flats end up on fingertips. If they are octagonal, our fingers end up sort of on flats but also on ridges. The draw to making them by hand octagonally is that it's easy - flatness of stock matches the pencil thickess, saw and then plane to a square and then remove top corners of the square until there are 8 visually equal sides.
but the pencils feel terrible.
I read later (always like to experiement first and then read - you get much more out of the reading if you'd stupid like I am, when you are preloaded with a little bit of experience and see something that would either be helpful or confirming. At any rate, I read later that pencils work octagonal at first. and before that, instead of being halves, they were more like a long box with a cap.
there are other things to overcome warping that I later solved by stabilizing wood after the fact with paraffin in mineral spirits - *after* the halves are glued.
paraffin dissolves in the mineral spirits (not sure what you guys call that - just petroleum distillates a little heavier than white spirit) and then can be soaked in the wood, and then as the mineral spirits dry, the wax is left, impeding moisture movement in the wood.
the amount that incense cedar warps even when it's sawn straight is pretty spectacular!
But short story long, I would like to make the leads to make a writing feel that is hard to match in smoothness and ease -drafting leads don't do it. They're a little dry and hard, probably for a functional reason.
micronized graphite is very easy to find, so the need in the old days to tumble it for a long period of time into a fine powder is no longer there. four or five dollars of micronized graphite will probably make 50 or 100 leads that are then basically fired like a ceramic pot.