For that kind of things, lead-holders are preferable: you at least get a consistent lead width, despite the wearing, assuming you maintain the orientation of the pencil.

An alternative is to sharpen your pencils with a utility knife & sandpaper: it's more versatile and less wasteful than a regular sharpener. For example, you could sharpen it to an edge (like a slotted screwdriver), and turn the pencil once in a while, so that the wearing helps preserving the edge.

I've also dabbled with Islamic patterns recently. Side-note: I've found some high-quality, cheap second-hand compass sets, that used to be used for wood work a few decades ago (not made-in-China).