Setting Roller Height

Since the general purpose of a press is to ink a printing surface and impress paper against it, roller height has a big part to play in quality printing. For the smallest printers there are the “small printer” approaches of setting large capital letters in the chase; inking those letters and then inspecting to see whether the face is inked, and whether ink has been transferred to the beard of the type. The ideal is to have fully inked the surface with a minimum of ink being applied to the beard of the type.

The next stage is to use a roller setting gauge. These come in various shapes and sizes. We’ll look here are the basic type that most small commercial printers would have. Flat gauges are typically a block of metal machined to 0.918” high with a long handle: and have the advantage that they tend not to tilt and so skew the results. The aim here is to see a thin film of ink over the surface. No ink indicates rollers are too high; and ink that has been smeared or left on the sides indicates rollers are too low.

Cylindrical gauges are more common but can tilt when used. The aim here is to see a thin strip of around ⅛th of an inch of ink on the top of the cylinder.

A further step to precision was to use a spring-loaded setting gauge that included a dial or marker to show how low the rollers were on the machine. I am yet to see one in use!

The Netherlands Graphic Arts Research Institute worked on establishing realistic tolerances for letterpress materials. They suggested that type would still print perfectly if it was within 0.0008” of 0.918”, and so any efforts to be more precise than that would be a waste.

F C Walter, writing in Print in Britain repeated that he had heard a lecturer stressing the need to be within an overall limit of 0.0015”, and commented that it would work “precision and the printer to death”. He foresaw that a “…printer, who has toppled, drunk with fascination into precision-land where everything is beautiful but useless.” He proposed an overall limit of 0.0030”. The reasoning was that 0.0015” could be so easily disrupted by standard printing processes (like planing) that it could not be achieved. In context 0.0015” is around ¾ of the thickness of a cigarette paper.