Hard rubber is easily worked with ordinary tools. Material of good quality turns cleanly on the lathe, and is neither gummy nor prone to chipping. When sawing hard rubber, a bit of water-based coolant/lubricant makes the job much easier and more pleasant, not least in reducing the sulphurous smell.
Hard rubber can be somewhat abrasive, especially older material incorporating substantial amounts of filler. Carbide tooling will greatly reduce the need for resharpening, though HSS is entirely suitable and even preferable for fine work where extra-sharp tool bits are called for.
Tool marks can be minimized by turning with a sharp tool with a bit of radius, using fast speed and slow feed. The workpiece can then be smoothed with 400 to 600 grit paper, preferably used wet, following up with 800 to 1000 grit or finer. Final polish can be done on a buffing wheel with tripoli, although one can also simply reverse the paper and use the back side for finish polishing on the lathe. Be very careful when polishing on the lathe: do not reach over the spinning chuck, and take care not to let the polishing strip get entangled in the work.
Hard rubber can easily be polished to a high gloss. Although some modern hard rubbers do not take a good polish, this should be seen as a defect, not an inherent property of the material. Vintage hard rubber articles were typically sold with a high-gloss finish; if a matte finish is desired, however, it is easy enough to use steel wool or a fine wire brush for a duller surface.
Ordinary solvents have no discernable effect upon hard rubber. It is generally recommended that petroleum distillates be kept away from hard rubber, since their ability to damage soft rubber objects is well-known, yet actual evidence of hard rubber being harmed by transient exposure is lacking. Hard rubber cannot be solvent-welded, but it can be readily glued with epoxies, cyanoacrylates, wood cements, and other common adhesives.
Hard rubber has certain working properties that set it apart from all other plastics. While it has great dimensional stability over time, it can readily be bent or molded with heat and pressure. Heat it until it is hot to the touch, and it turns rubbery; let it cool, and it will gradually reharden. Although it will scorch if it gets too hot, hard rubber remains elastic over such a broad range of temperatures that one can easily mold it using nothing more than a heat gun (or the traditional pensmith's heat source, an alcohol lamp) and one's fingers. And unlike other plastics, hard rubber will spring back to its original form and dimensions once reheated. Hard rubber is thus an optimal material for components that have to be press-fitted, such as nib/feed/section assemblies.
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