The twist drill is type most commonly used of all drills. It can be used in electric hand drills and CNC lathes. For us, what materials can be drilled with twist drills? Only by understanding this will we be able to properly use twist drill and drill quickly and safely.
In fact, a twist drill can drill metal, concrete, wood, ceramic tiles, glass and other materials. When drilling alloy steel, cast iron and other metals, use black high speed steel twist drills. Glass and ceramic tiles have high hardness and poor toughness. When drilling holes in such materials, it is necessary to choose tungsten-carbon alloy twist drills with higher hardness.
After use, twist drill becomes dull and not sharp enough, requiring drill to be sharpened. So, when sharpening, how best to sharpen it?
Pay attention to following points:
1. Keep blade flush with surface of grinding wheel
Before sharpening drill, make sure it is correctly positioned, place drill in same plane as surface of grinding wheel. When blade comes into contact with grinding wheel, you can not only hit part of it, but also sharpen everything.
2. The center line of twist drill deviates from surface of grinding wheel by 60 degrees
Twist drills made by many people are not easy to use because they don't grip corner well. If angle between center line of drill and surface of grinding wheel is too large or too small, drill will be especially dull, so grinding is pointless.
3. The top and bottom edges should sway back and forth, and tail should not be lifted too high
When sharpening twist drill, hold drill firmly in your hand and swing it back and forth on grinding wheel. Please don't lift your tail too much. Otherwise, blade will be blunt, unable to cut properly, and grinding effect will be especially bad.
4. The tip of blade should be symmetrical on both sides
Sand one side first, then other. Be sure to take care that two sides are symmetrical and repair them slowly. The gap between two sides should not be too large, and one side should not be sharp while other should be flat.
5. Sanding from edge to back
When grinding, after tip of knife touches grinding wheel, it is sharpened from main cutting edge back, starting from cutting edge of drill to touch grinding wheel, and then slowly sharpened down entire drill back.