Basic Machining Tools

Common Machining Tools and Their Uses

Machine shops use many specialized tools, each designed for particular materials and operations. Understanding a tool’s intended purpose is essential before selecting or using it. Experience with different tool geometries, materials, and coatings will help machinists determine which option works best for each job.

End Mills

End mills are among the most frequently used tools on milling machines and CNC machining centers. They can side-mill the ends of a workpiece, create clean parallel surfaces, cut pockets, and produce square or rounded features.

Important end-mill selection variables include:

• Cutting diameter
• Flute length and overall length
• Tool material and coating
• Roughing or finishing geometry
• Number of flutes
• Workpiece material

Drills

Drills create holes, but the correct drill depends on the workpiece material, required depth, diameter tolerance, and production volume. General-purpose 118-degree high-speed-steel or coated drills work with many common materials, while difficult alloys, deep holes, and close-tolerance features may require specialized tooling.

Taps

Taps produce internal threads in prepared holes. Selection depends on the thread standard, required size, workpiece material, and whether the hole is blind or passes completely through the part.

• Cut taps remove material and produce chips. Chip evacuation must be considered, particularly in blind holes.
• Roll-form taps displace material to form threads without producing chips. They can be useful in suitable ductile materials and blind-hole applications.
• Spiral-point and spiral-flute taps control the direction in which chips move.
• Thread mills produce threads through a circular CNC toolpath and can offer flexibility across compatible thread sizes.

The tap-drill diameter must suit the selected thread and tapping method. Form taps generally require a different prepared-hole diameter than cutting taps.

Reamers

A reamer finishes an existing drilled or bored hole to a more accurate diameter and surface finish. The initial hole is normally made slightly undersize so the reamer removes a small, controlled amount of material.

A reamer follows the existing hole and should not be expected to correct substantial misalignment, curvature, or out-of-roundness. When hole location, straightness, or geometry must be improved, boring may be required before reaming.

Basic Tool-Selection Principles

• Match the cutting tool to the workpiece material and operation.
• Check the drawing for size, tolerance, finish, depth, and thread requirements.
• Choose geometry and coatings appropriate to the cutting conditions.
• Provide suitable chip evacuation and cutting fluid where required.
• Follow the tool manufacturer’s recommended speeds, feeds, and hole-preparation dimensions.

Read the source article: Basic Machining Tools – Terminology