On
a single cut bur all the flutes spiral in the same direction, generally this
configuration produces less aggressive cutting action and leaves a smoother
finish.
The bur in (fig. 1) is a straight side (no-tapered), flat end (no-radius),
with no end cut.
On a double cut (diamond-cut) bur there are additional flutes spiraling in the opposite direction, generally this configuration produces a more aggressive cutting action i.e., the crisscross pattern provides a chip breaking feature that produces finer chips increasing its efficiency, the finish may however be rougher than the single cut.
The flat end of a bur can be configured without Flutes (Fig. A) or with flutes (Fig. B). Having flutes on its end will allow the bur to perform milling using only the bottom of the bur additionally it can be used to plunge mill i.e., somewhat similar to drilling (will be shown on another page).
The end of a bur that is rounded (Fig. 4) is called a radius end and the flutes (single or double cut) extend around the radius. This bur can create a chamfer at the bottom of the cut ( will be shown on another page) it can also be used to plunge mill.
The sides of a tapered bur typically vary from 2 to 10 degree.
They can be single or double cut (Fig. 5) shows a single cut.
The angle is calculated using only one side i.e., 1/2 the "total" angle of
the bur (sometimes called a line angle or a half angle).
Burs used in photographs are for illustrative purpose.