Tools you might need next
Calculate glaze batch weight from unity formula and raw material analysis. Scale recipes to any batch size for consistent studio pottery glazing.
Create kiln firing schedules with ramp rates, hold times, and cone temperatures. Plan bisque and glaze firings for electric and gas pottery kilns.
Calculate clay shrinkage percentage from wet, dry, and fired dimensions. Plan pottery sizes accurately for clay bodies from leather-hard through glaze firing.
Pricking iron pitch (mm between holes) should match leather thickness and thread size. Fine goods use 2.5–3.0 mm; belts and bags use 3.5–5.0 mm pitch.
Pitch chosen by leather oz: ~1/3 of leather thickness in mmDivide seam length by pitch to get approximate hole count. Adjust start/end offsets so holes are symmetric and corners have adequate spacing.
Hole count ≈ seam length / pitch (round to nearest integer)Holes are typically set one pitch distance from the edge, or half the leather thickness, whichever is smaller, to prevent edge tear-out.
Edge distance = min(pitch, thickness / 2)Updated: July 2026
3.0 mm pitch on 3 oz leather: 80 / 3.0 ≈ 27 holes. Set back 2 mm from edge; mark from center outward for symmetric end spacing.
Belt perimeter 900 mm at 4.0 mm pitch: ~225 holes. Use round awl through pricking marks; two needles consume one thread length per pitch.
Gusset seam 120 mm at 3.5 mm pitch with 5 mm corner radii: reduce pitch near corners or pre-mark to avoid bunching on curved pricking lines.
Score a stitching groove with an edge creaser first. Holes punched without a groove wander visually and weaken the edge grain.
Laminated seams (lined vs unlined) need pitch matched to the thickest effective layer. Skived edges can use finer pitch than full-thickness sections.
Even stitch spacing is essential for professional leatherwork. This calculator determines hole count and spacing along a seam from stitch length, pricking iron pitch, and edge offset for saddle-stitched projects.