Uneven leather stitching almost always has a specific cause rather than being a general skill problem. The five most common causes are inconsistent pricking iron holes, unequal tension between the two needles, thread twist, a shifting stitch angle, and a thread-to-hole mismatch. Work through each cause systematically and the problem will narrow down quickly.
Traditional pricking irons mark spacing for an awl, while modern through-punch irons and stitching chisels can form holes directly. Learn when each method applies.
A pricking iron sets the stitch spacing and hole profile for all hand stitching. French-style irons produce narrow, slanted slits. Diamond-style irons produce diamond-shaped holes. The finished appearance also depends on spacing, thread, leather and stitching technique. Spacing — typically 3mm to 4mm for most hand leatherwork — should match the leather weight and thread size.