Tech Talk
What is the "Relief Angle" of a cutting tool?
Relief may be defined as the amount of stock removed from the teeth behind the cutting edge to permit the teeth to cut freely and to clear the material after the cutting edge has done its work.
It is important that the relief angle be correct. If it is insufficient, the teeth will have a dragging cut, while if it is too great, the teeth will wear rapidly, and the cutter is likely to chatter. Too much relief, however, is less objectionable than too little.
The proper relief angle depends upon a number of factors, principally the type and diameter of the cutter and hardness of the material to be machined. For example, cutter employed on soft materials like brass can stand more relief than those employed on steel or cast iron. Likewise, the relief must be greater for small cutters than for large ones. For these reasons, it is generally agreed that the correct relief angle for a given cutter must be determined by experience. Once the relief angle (as well as cutting speed and fee) that gives the best results on a certain operation has been determined, it should be recorded for future reference.
