I am a apprentice machinist and I am drilling center holes with a center drill. A senior machinist told me to "Use type A or type 2 center drill to produce the formed hole", but I am not sure what they are.
How many types of Center drills are there?
There are four major types of center drills, "Type A", "Type B", "Type C", and "Type R" (incorporating ISO standards), specified by JIS standards.
However, in addition to the above 4 types, the old JIS standard "Type 1" and "Type 2" are still in use, so it's a bit confusing. Please refer to the explanation below for the difference in those types of center drills!