Factors affecting the choice of knife angle:
(1) the type of microtome
(2) the knife, especially the size of the bevel for the cutting edge and the knife’s profile
(3) the hardness of the material being cut
(4) the thickness of the section
(5) the speed of cutting
The clearance angle is the angle between the plane of the specimen surface and the plane of the knife’s bevel closet to it.
A common angle to start with is around 30 degrees.
If the knife angle is too shallow then:
(1) cutting may be erratic with irregular sections
(2) sections may stick to the knife
(3) sections may be skipped
(4) the specimen may be subjected to too much pressure and excessively compressed
(5) sections may alternate between thick and thin
If the knife angle is too high then:
(1) the blade edge may be damaged
(2) section thickness may vary
(3) the tissue may be scraped rather than cut
(4) the section may roll up if the specimen is soft or shatter if it is hard
Other factors that can alter angle performance:
(1) if any of the components are loose
(2) if the blade is dull or dirty.
(3) if the microtome is malfunctioning
