Een serieus nadeel merk ik als je de keerbeitel een flauwe vouw van 30 graden geeft, is dat deze eigenlijk te zwak is. Mits je keerbeitel gewoon van zacht staal is gemaakt. Hij gaat snel rafelen en door de druk van de wig krult deze op heel microniveau een beetje een braam aan de rand. Dit bemerkte ik gisteren bij fijne afname, terwijl mijn beitel net geslepen was, ik begon te twijfelen aan of deze wel scherp was. De keerbeitel had zich was zich als een soort versnipperaar aan het gedragen.
Zo denk ik nu dat een naar 45 graden afronden of een 2e vouw van ongeveer 1 a 2 tiende mm beter is. Zo zijn we weer terug bij af, eigenlijk begrijp ik steeds beter waarom in alle boeken deze configuratie staat.
Holzapfels: pagina 480/481 volume 2, The wide mouth allows a partial splitting of the fibres before they creep up the face of the single iron; this plane works easily, and does not greatly alter the shavings, wich come off in spiral curls, but the work is left rough and torn.
A similar but less worn plane with a closer mouth, allows less of the splitting to occur, as the shaving is more suddenly bent in passing it's narrower mouth, so that the cutti now begins to exceed the splitting, as the wood is held down by the closer mouth: the shaving is more broken and polygonal, but the work is left smoother.
The same effects are obtained in a much SUPERIOR manner in the planes with double irons, such as in fig. 325, the top iron is not intended to cut, but to present a more nearly perpendicular wall for the ascent of the shavings, the top iron more effectually breaks the shavings and is thence sometimes called the break iron.
Now therefore, the shaving being verry thin, and constrained between two approximate edges, it is as it were bent out of the way to make room for the cutting edge, so that the shaving is removed by ABSOLUTE cutting, and without being in any degree split or rent off.
The top iron has a true edge, wich is also moderately sharp and is placed from ONE SIXTEENTH TO ONE FIFTIETH of an inch from the edge of the cutter, the two are held together so closely by the screw which passes through a long mortise and fits in a tapped hole.
THE CONSTANT EMPLOYMENT OF THE TOP IRON IN ALL AVAILABLE CASES, SHOWS THE VALUE OF THE IMPROVEMENT; AND THE CIRCUMSTANCES OF THE PLANE WORKING THE SMOOTHER, BUT HARDER, WHEN IT IS ADDED, AND MORE SO THE CLOSER IT IS DOWN, DDEMONSTRATE THAT ITS ACTION IS TO BREAK OR BEND THE FIBRES. THIS IS PERTICULARLY OBSERVABLE IN THE COARSE THICK SHAVINGS OF A DOUBLE- IRON JACK PLANE, COMPARED WITH THOSE OF THE SAME THICKNESS FROM A SINGLE- IRON PLANE; THE LATTER ARE SIMPLY SPIRAL AND IN EASY CURVES, WHEREAS THOSE FROM THE DOUBLE-IRON ARE BROKEN ACROSS AT SHORT INTERVALS, MAKING THEIR CHARACTER MORE NEARLY POLYGONAL; AND THE SAME DIFFERENCE IS EQUALLY SEEN IN THINNER SHAVINGS, ALTHOUGH OF COURSE LESS IN DEGREE.