For anyone involved in precision machining, understanding what a reamer is and how it functions is fundamental to achieving the tight tolerances that modern engineering demands. A reamer is a multi-fluted cutting tool designed to enlarge and finish previously drilled holes to precise dimensions, typically achieving tolerances as tight as H7 (0 to +0.015 mm for a 10mm hole).
Unlike drill bits, which are designed for material removal, reamers remove only a small amount of material — typically 0.1 to 0.4 mm on the diameter — to improve surface finish, dimensional accuracy, and hole geometry. This makes them indispensable in applications ranging from automotive engine blocks to aerospace components and medical implants.
Types of Reamers
Reamers come in several configurations, each suited to specific applications:
- Straight flute reamers — The most common type, ideal for general-purpose through-hole and blind-hole reaming in steel, cast iron, and non-ferrous materials.
- Spiral flute reamers — Better chip evacuation makes them suitable for blind holes and interrupted cuts.
- Carbide reamers — Offer superior wear resistance and longer tool life, especially in hard materials like hardened steel and superalloys.
- Step reamers — Combine multiple diameters in a single tool, reducing cycle time and tool changes.
For manufacturers working with hardened steel, the H7 tolerance CNC straight flute reamer from OPT Cutting Tools delivers exceptional wear resistance through its metal-ceramic construction, maintaining dimensional accuracy even after thousands of holes.
How to Use a Reamer Properly
Proper reaming technique requires attention to several factors: the pre-ream hole should be drilled 0.1–0.4 mm undersized; cutting speeds should be approximately one-third of the drilling speed; and coolant should be applied generously to flush chips and reduce thermal expansion. For through-hole applications, the left-turn right-cut finishing reamer provides excellent surface finish and chip flow.
In specialized forming applications, a carbide forming knife can complement the reaming process by creating complex hole profiles that standard reamers cannot achieve.
Reamer Speeds and Feeds
Optimal reaming parameters vary by material: for carbon steel, speeds of 15–25 m/min with feeds of 0.2–0.4 mm/rev are typical; for stainless steel, reduce speed to 8–15 m/min; for aluminum, speeds can reach 50–80 m/min. Always consult the manufacturer’s recommendations for specific tool geometries and coatings.
Post time: Aug-11-2026