1/2" diamond drill bit

Diameter:1/2", shank:3/8"
Fits nearly all portable drills or hand held drills. Fits Drill presses.
For all hand held portable drills, start your drilling at a 45 degree angle. Create a groove for your diamond drill bit to follow. Tip your drill bit upright to a 90 degree angle.
Finish the hole using less pressure to break through to prevent chipping.