These pre-preg sheets of graphite-plus-binder are tightly wrapped around a solid steel forming mandrel (a mandrel is a metal rod around which other material is formed into shape). The mandrel dictates the inside diameter, or core, of the shaft. That diameter, plus the number of layers wrapped around the mandrel and the variety of pre-preg material used, determines the weight and stiffness of the shaft.
More layers wrapped around the mandrel equals greater wall thickness, which equals a stiffer and heavier shaft.
In addition, greater stiffness can also be achieved by using stronger and stiffer sheets of pre-preg. In this manner, the shaft walls can be thinner - but still have enough stiffness - to achieve a lighter weight in the shaft.
Once all the prescribed individual layers of the pre-preg graphite material are tightly wrapped around the forming mandrel, a thin wrap of cellophane is added over the shaft to hold the pre-preg layers in place. The shafts are then put into special ovens whose heat causes the binder material to slowly "melt," fusing all the pre-preg layers together into one contiguous tube of graphite.
After baking, the forming mandrel is pulled out of the inside of the shaft through the grip end of the shaft. The cellophane covering is stripped off, the shafts are sanded smooth on their surface and then painted in the cosmetic scheme dictated by the customer.
