Thermo Scientific HM340E Operation Manual page 51

An angle, which is too steep, is also unfavorable as the knife/blade might vibrate too much while sectioning. The
so-called "chatters" appear on the block surface as well as on the sections as parallel stripes having negative effects
on the microscopical evaluation.
Between these two limit cases, the correct knife angle must be determined. A clearance angle between facet angle
and block surface of approx. 5° is normal.
Different microtome producer use different scaling for their clearance angle adjustment, resulting
from different calculation bases. The clearance angle might refer to the facet surface or to the angle
between knife main surface and block surface. As the facet has a divergence from the knife main
surface of approx. 5°, the resulting difference is approx. 5°. Therefore, set the correct angle on
Thermo Scientific instruments at 10°.
Thermo Scientific Rotary Microtome HM 340E
51