In answer to Roger's question, there are indeed many graphites suitable for instrument making. Below is an abbreviated list of some of the graphites commercially available.

Graphite, True Central American (Graphitus graphitus)
Graphite, African (Carbonus psuedographitus) Graphite, Bastard (Psuedographitus nilpater)
Graphite, False (Psuedographitus psuedographitus)
Graphite, Heavy african (Carbonus wezatunnus)
Graphite, Honduras (Graphitus graphitus)
Graphite, Jamaica (Graphitus noshecameofherownaccordus)
Graphite, Sapele (Psuedographitus cheapus)
Graphite, Curly (Graphitus koa ssp. Hawaiensis)
Graphite, Birdseye (Graphitus saccharographicus)

Of these, most reputable graphite instrument makers will of course stick with the genuine Graphitus graphitus using only high-grade aeronautical adhesives although the Curly and Birdseye graphites are beginning to find favour at the high end of the market but are rather expensive.

It is very important to avoid the use of some so-called "graphites", often of Far Eastern origin, which unscrupulous suppliers will often try to pass off as the real thing. Examples include:

"Graphite, Taiwanese" (Plasticus flexibilis)
"Graphite, Chinese" (Notonus sinensis)

I would not recommend these for instrument making.

I hope this is helpful.

mooman