We are pleased to now offer cap irons to our line of tools. Cap irons, or chip breakers, when used in conjunction with a cutting iron, are meant to control tear out in double iron planes. By setting the leading edge very close to the cutting edge, the shaving is forced into a tight curl that breaks the fibers before they can lift in front of the cutter, which is the primary cause of tear out.
We worked with contemporary double iron plane maker Steve Voigt, of Voigt Planes, when developing these cap irons. Steve has done extensive research in double irons planes and has numerous articles and links on his site about the theory and use of cap irons.
Our cap irons are made of mild steel, and are not hardened. The front has been formed with a bend to ensure tight contact against the cutting iron. a smooth radius is machined onto the top surface and the tang is machined with decorative bevels similar to our tapered irons. A threaded hole and screw are included.
Please note that a bevel will need to be honed onto the leading edge of these cap irons. The leading edge is as machined; it has not been deburred. We recommend the bevel to be .020″-.050″ wide, and at an angle of 50° or so. This bevel is critical for the cap iron to work properly; too small and it won’t work. and to large and the plane will clog. It is also critical that the leading edge be thoroughly deburred using medium and fine stones, followed by a strop. Because the steel is soft, this burr can be persistent and will take some back and forth to remove it entirely. Keep the edge sharp during this process so shavings cannot jam under it.
Once the edge is dressed, it should not need any maintenance for years, if ever. When planing resinous woods, resin can build up on the cap iron. Simply remove with a rag dampened with mineral spirits or acetone.