On this side of the lake these bits are known as "brad-points"...There is another similar
type known as "Forstner", but they are much more expensive and I am not sure they are
available in the smaller diameters...
After a few days use, I've found the diamond core drills to work pretty
well for making island pads. Depending on where you purchase them and
the drill size, the price runs between $4 and $12 each. They seem to be
available commonly on Ebay as sets from Hong Kong. Domestic US sources
are more expensive. The diamond core drills are used in stained glass
and rock collecting hobbies. They are a true core drill and do not cut a
center hole. This also means the work can get away from you if not
clamped to the drill press table.
I have 5 mm (3/16"), 7 mm (1/4") and 8 mm (5/16") core drills and find
myself using the 7 mm more than the others.
Jack K8ZOA
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