Web thinning for the twist drill bits

After removing the worn areas of the twist drill bits, the next step is to restore the approximate web thickness of the drill, which has been shortened. The webs in the most twist drill bits increase in thickness towards the shank. After removing the worn areas of the drill bits, the exposed area will have a larger web area. The longer edge would require more power and would result in shorter drill life. To prevent this, it is necessary to restore the chisel length to its previous size by reducing the web thickness. This procedure is called web thinning. While web thinning for the twist drill bits can be performed manually, machine grinding is preferred for most accurate results. Whether thinning is done by machin or an experienced operator, the grinding wheel used should be soft enough so it does not burn the cutting edges while removing the stock.

  It is important that the web be thinned evenly on both sides so that it remains centered in the drill. Also thinning should not be carried too far up the web, as this would weaken the drill. Since chips that form on the lips must flow into the flutes, thinning should be gradual to prevent interference with chip flow, which can eventually break the drill.

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