So what is the difference between Carbon Fiber (carbon fibre) and Graphite when referring to fly rods?
In short, absolutely nothing.
Or perhaps more correctly - the Atlantic Ocean.
In the US, fly rods made from Carbon fibre are referred to as Graphite fly rods. Everywhere else in the world they are referred to a Carbon Fiber, or more correctly Carbon Fibre.
In the same way that in the US sections of a motor vehicle are referred to as “trunk", “windshield” and a “hood” - Whereas those in the UK, New Zealand and Australia refer to these items as a “windscreen”, “boot”, and a “bonnet"
Carbon fibre as used in fishing rods is produced from polyacrylonitrile (PAN) fibres which are bonded with resins. Prior to being bonded the woven fibres are called “pre-preg”.
What is Carbon Fibre?
Carbon Fibre is man-made - where the molecular structure is synthesised. And we use this material to make fly rods, mountain bike frames, golf club shafts and race cars.
Carbon fibre is light, stiff and very strong - just the ticket for high performance fly rods
Carbon fibre was first manufactured in its coarse state by Union Carbide in the USA. However the first viable carbon fibre for use in the fishing tackle industry was discovered by Jim Hardy of Hardy Bros and the famous angling writer Richard Walker. Walker had had wartime connections with the Royal Aircraft Establishment in Farnborough and he introduced Hardy to Leslie Phillips who was conducting research into carbon fibre.
Samples of the material were taken back to Alnwick but it was some time before Hardys themselves produced carbon fibre rods. They wanted to see how the market would respond to the new material.
Natural graphite in it's raw state - not for fly rods
What is Graphite?
Graphite is a naturally occurring form of crystalline carbon. It is a native element mineral found in metamorphic and igneous rocks. Graphite is a mineral of extremes. It is extremely soft, cleaves with very light pressure, and has a very low specific gravity. In contrast, it is extremely resistant to heat and nearly inert in contact with almost any other material. These extreme properties give it a wide range of uses in metallurgy and manufacturing.
Graphite, although a form of carbon, is different; it is produced in many ways, often as a flat sheet or as pencil leads for example. Graphite also has lubricating properties. Eg dry graphite power and graphite grease.
Graphite is a natural material (sourced predominantly from China and India - and in its unprocessed state certainly no use at all for rods)
Differences Between Graphite and Carbon Fiber
https://sciencing.com/info-12025349-mechanical-properties-jis-scm-420h-steel.html
The terms graphite and carbon fiber have become interchangeable to some extent. However, graphite in lead pencils and graphite in a tennis racket are obviously not the same material.
The stuff that makes a strong tennis racket is made of carbon fibers. Both graphite and carbon fibers are carbon-based; the differences lie in the process that produces the end product.
