Point and Pica Conversion Tables

1. Introduction

If you are casting type using American or English machinery, you need a table of points converted into inches. You'd need this even in a perfectly equipped shop which had micrometers which read natively in points, but as such micrometers are scarce indeed, under the assumption that you don't have one (I don't), you'll need such a table constantly.

While direct point-reading measuring tools are scarce in printing (and most typecasting) shops, direct pica-reading tools are common. They tend, though, to be of a semi-precision variety (e.g., the printer's line gauge, or "pica stick"). Once common tools such as the typefounder's "72 point gauge" (which is really just a "6 pica gauge," of course) are now scarce. The most accurate pica-reading tool in an ordinary printing shop (at least a hot metal shop) might well be the gauge on the printer's saw.

This may be adequate for the printer, but it is not sufficient for the typefounder (or indeed the linecaster). The typefounder needs to be able to replicate the "72 point gauge" using common inch measuring tools (micrometers and calipers). The linecaster preparing cast borders for sale needs to know exactly how long a cut slug is, not roughly to the pica as shown on a pica stick, but exactly to the fractional pica (measured with the only tool available - an inch-reading vernier, dial, or digital caliper).

These tables could have gone in several different sections of CircuitousRoot. Indeed, I most often use them when casting type on a sorts caster, so perhaps I should have put them in one of the Noncomposing Typecaster Notebooks. They might also reasonably have gone in one of the Type Machinery Operation Notebooks. They had to go somewhere, though, so they are here.

2. Point Conversion Tables

3. Pica Conversion Tables

Here are two pica conversion tables. These are simply LibreOffice spreadsheets. I've computed them up to 36 points only, as 6-inch calipers are common, but you could easily extend them.

4. Point Conversion Table Data and Program

pointchart.c

Use this command to compile it: cc -lm -o pointchart pointchart.c

usage: ./pointchart LessThanPoint DivisionsPerPoint Places NumColumns

LessThanPoint must be a reasonable integer.

DivisionsPerPoint must be 0, 2, 4, or 8 for whole points, half points, quarter points, or eighth points, respectively.

Places must be 3, 4, 5, or 6.

NumColumns may fail for extreme values.

The output is a sort of a "comma separated value" list (redirect it to a file), save that the separator is a semicolon rather than a comma (the comma is used as the thousands separator in the decimals). The format is American, with a period for the decimal point. Fractional points are expressed as fractions in ASCII text.

You could import the output into a spreadsheet. I find spreadsheets to be fairly limited in terms of features to make the table look pretty, though. What I did to create the tables here was to import the output file into OpenOffice Writer (Insert -> File). I then highlighted the table and used Table -> Convert -> Text to Table. I added the final value (e.g., 24 point, 48 point) by hand. (The program calculates from zero up to but not including the final integral value. This is necessary to get a nice table which divides up so that integral values head each column.) Then I fiddled with the formatting. The typeface is Linux Libertine, which is reasonably nice.