The clearance angle of the microtome blade is routinely

• A. 1-2
• B. 3-8
• C. 9-12
• D. 15-20 degrees

Answer: (B)

The clearance angle is the small tilt between the blade edge and the surface of the tissue block that prevents the edge from scraping along the block during cutting. For routine paraffin sections, a modest clearance angle provides a clean shear cut without rubbing the block or dulling the blade. This balance is typically in the 3–8 degree range.

If the angle is too small, such as 1–2 degrees, the blade doesn’t clear the block enough and tends to rub the surface, causing chatter, tissue tearing, and faster dulling. If the angle is too large, like 9–12 or 15–20 degrees, the blade loses sharpness and the cut becomes less precise, leading to thicker, compressed, or uneven sections. Therefore, the routinely used clearance angle is about 3–8 degrees, which optimizes both cutting quality and blade longevity.