Basic Machining Tools: Reamer

What Is a Reamer?

A reamer is a multi-edge cutting tool used to enlarge and finish an existing hole. It removes a small amount of material, improving the hole’s diameter, roundness, and surface finish.

How It Is Used

The hole is first produced slightly undersize with a drill or another machining operation. The reamer is then aligned with the hole and advanced steadily through it.

• Choose a reamer that matches the required finished diameter.
• Leave only a small, appropriate amount of material for reaming.
• Secure and align the workpiece carefully.
• Use suitable cutting fluid for the workpiece material.
• Run the tool at an appropriate speed and feed without stopping inside the cut.

Common Types

• Hand reamers: Operated manually and commonly made with a lead-in taper.
• Machine reamers: Designed for use in drill presses, lathes, milling machines, and CNC equipment.
• Adjustable reamers: Permit limited diameter adjustment within a specified range.
• Taper reamers: Produce or finish tapered holes rather than straight cylindrical holes.

Good Machining Practice

A reamer is a finishing tool, not a substitute for drilling or boring away a large amount of stock. Excess material, poor alignment, an unsuitable cutting speed, or damaged cutting edges can produce an oversized, tapered, or rough hole.

Keep the tool clean and sharp, avoid reversing it while its cutting edges remain engaged, and verify the finished hole with an appropriate measuring instrument.