Pricking irons and stitching chisels are tools for marking or piercing evenly spaced holes for stitching in leather.
Terminology
Makers and sellers don’t name these tools consistently. Some reserve “pricking iron” for tools designed just to make marks for piercing with an awl as a separate step and “stitching chisel” for tools designed to be driven through the leather layers in one step.
Sizing
Manufactures differ in how they number their irons and chisels, as well as related tools like fudge and overstitch wheels.
Many manufacturers now size their tools by distance, stated in millimeters or fractional inches. Sometimes the figures refer to the distance from the point of each tooth to the next. Sometimes the figures refer to the distance from the leading edge of each tooth to the trailing edge of the next.
Some English and American manufacturers continue to number by stitches per inch. Examples: Tandy/Craftool, Osborne, Dixon
Traditional French manufacturers number by stitches per Paris inch. Example: Vergez Blanchard
Some older Japanese manufacturers number by teeth—and resulting holes, not stitches—per sun (寸).
Shape
Both pricking irons and stitching chisels come in a variety of point shapes: round, diamond, or chisel. Some more recent tools use removable and interchangeable points fixed by set screws.
Some manufacturers refer to tools with chisel-shaped points as “European” or “French” and tools with diamond-shaped points as “Japanese”.
Tools may also be offered with reverse-shaped points. Reversed tools allow makers to mark or pierce holes from both sides of a potential seam.
Teeth
Individual tools may have as few as one and as many as a dozen or more teeth.
Tools with two teeth offer the most flexibility around corners. Tools with many teeth cover long, straight lines more quickly. However, tools with very many teeth may require more force, or even a press rather than a mallet, to drive through.
Single-tooth tools are essentially awls. Some use them for marking or making holes in the bends of sharp corners, which may be spaced and oriented somewhat differently from surrounding holes.
While some manufacturers promote “complete” sets of tools with several different numbers of teeth, many makers two tools—one with two teeth and another with four through up to eight teeth—sufficient.
Technique
Pricking irons and stitching chisels are typically laid on a line, which may be marked with pen or pencil, scratched with a compass or scratch awl, or cut in with a stitching groover. The tools are then tapped or driven into the leather using a mallet. The face of the mallet should be softer than the metal of the tool, such as of rubber, plastic, or rawhide, or covered with such, so as not to deform the striking face of the tool.
For consistent appearance, it’s important to place the tool consistently, relative to the line. Diamond teeth have points that are easily centered on the line. Round and chisel teeth may be centered over the line or placed with one edge against it.
Lines are continued by setting the first tool of the tool in the last mark or hole of the last drive. Some makers may overlap two or more.
The tool is drawn directly out of the leather, without tilting or twisting. Some makers place slotted plates around their tools as they mark, pushing the plate down as they pull the tool, to keep the leather from bending up and away from the work surface due to friction holding it to the teeth of the tool.
Alternatives
Pricking irons serve much the same purpose as overstitch wheels and fudge wheels, marking holes for stitching at regular intervals.
Larger hole spacings can also be marked with a compass fixed open to a particular distance. Mark two holes with the points of the compass, then rotate the compass, leaving one of the points in its hole, until the other point swings to the intended stitching line. Mark the new point, pivot around it, and continue. This method is often used for marking relatively large even spacings, such as between eyelets or lace hooks.