Notes Random

1. Best drill bits to buy, even if you are drilling rocks: PDC = poly crystaline diamond compacts
2. Why Tungsten Carbide drill bits are better than HSS drill bits?
1. Tungsten carbide drill bits have to be sharpened only by diamond wheels, so their sharpening is done on good machines whose angles are controlled precisely. So they make better drill bits
2. HSS drill bits are cut in normal grinding wheels, so their angles may not be as precise and process may not be strictly controlled. This results in poorer drill bits in the end
   
3. Both Cobalt and Nickel are used as binder in Tungsten Carbide drill bits. When nickel is used, the bit is slightly magnetic. When cobalt is used ?
   
4. Cobalt has higher thermal expansion and so when Cobalt binded Tungsten Carbide drill bits are used for long, due to thermal expansion, they may fail.
5. Always have UV seals next to the commutator brushes in the motor. Constant sparking of the commutator brushes give out UV light and the light damages the polymer cage of the bearing and the grease.