Hubshell. A pattern from which a hub is cut on a pantographic reducing machine. Hubshells are oversize positive patterns, and can be made by any of several processes, as electroformed galvanos, or foundry casts, epoxy shells, or, conceivably, any hard modelled substance. Dies cannot be cut from these, only hubs (then hubs used to sink dies). A hubshell is to a hub as a dieshell is to a die – both patterns; the difference, of course, is that both hubshell and hub are positive, both dieshell and die are negative.

Since a hubshell is positive it looks like a large coin or medal; in fact galvanos made for wall mounting are the same as hubshells with several minor differences – hubshells have a flange for attaching to the pantograph, wall mounted galvanos are usually trimmed for artistic or aesthetic reasons. Also wall mountings are given a patina finish, hubshells have no need to be finished.

A hubshell is required for any direct cutting; the creating of a completely formed object by pantograph. Since the required object must be positive, its pattern – the hubshell – must be positive.

See hubbing, dieshell.