ALTANA DIN EN ISO Impact Tester - Handbuch (Seite 26)

5. Remarks
There are instruments on the
market in which the die diameter
is only slightly larger than that of
the impact ball.
Under large impact energy, this
may cause shearing of the test
sample between the ball and the
rim of the die, preventing further
penetration of the ball into the die
bore (particularly important in the
case of coil coating).
A falsely optimistic result is then
obtained. For the ratio of ball
diameter and die bore in impact
testing instruments please refer to
the relevant standards.