A harness cannot be in too perfect condition or too well cared for, both ensure the safety of the rider (or driver) and the horse. Still, they are not cheap. A handcrafted leather draft work harness from starts at £324. (February 2010 prices.) There is nothing magic about repairing harnesses, but you will need specialised cutting and stitching tools. Moreover, you will need to purchase the right grade of harness leather (which is heavyweight 227 to 284gr leather) from a quality retailer. You may always reuse the harness hardware, which is very rugged, but replace any worn or cracked straps entirely.
You will not be able to use heavy shears or a simple craft knife on 8 to 12-oz. harness leather. This leather is very thick, more like the sole of a shoe than like a leather jacket. A round knife is a half-moon-shaped blade attached to a sturdy handle. It resembles a Japanese vegetable chopper. Strap end punches are heavy, curved blades at the end of a handle. They allow you to cut a neat strap end with the stroke of a mallet. These come in sizes between 1-1/4 to 1-3/4 inches.
Punching tools enable you to drive holes for any hardware or buckles (much like your belt holes). A rotary punch tool is adjustable with a rotating wheel, and shaped like pliers. These can punch holes typically between 1/8 inch and Â¼ inch. Drive punches do the same, but require a mallet. Each drive punch comes in an individual size (like 1/8 inch or 1/4 inch). These are more expensive: a rotary punch retails at $16.99, versus $14.99 for a single 5/16-inch drive punch. (February 2010 prices.) Drive punches are better suited to heavy harness leather.
A mallet or maul is made of a heavy poly material or rolled leather. The lighter wooden mallets that leather crafters use are ill suited to heavy harness leather. Leather working mallets are never made of metal, as the strike of metal on metal damages the tools (and endangers the craftsman).
You may use a sewing awl or hand-stitching tools. A sewing awl combines a heavy handle, heavy needle, and a bobbin of heavy-duty waxed thread. Hand-stitching tools include harness needles; a leather awl, to open holes before you stitch them; and the heavy-duty waxed thread. Lacing nippers are pliers-like devices, which allow you to punch straight lines of lacing holes along the edge of the leather. These are also available in punch form. Palms and thimbles provide support for your wrists and fingers for hand stitching.
Other Tools and Materials
You will require leather cement to both stabilise the leather and add strength to the finished work. You may wish to invest in a lacing pony, a type of vice which holds the leather in place while you stitch. These come in inexpensive tabletop varieties of under $20, to hardwood foot-pedal designs of $125 or more.