Understanding the Design and Function of a Cutting Tool

Cutting tool

A cutting tool is one used to remove material from an object through shear deformation. This can be done using single-point or multipoint cutting tools, depending on the method and means of deformation you need.
A single-point cutting tool is one which uses a single cutting edge. These can be used to shape or plane an object. Examples of multipoint tools are milling, drilling, and grinding tools. There are two means by which a tool can move:

  • Linear – – Linear cutting tools those which have a tool bit or have single-point tools in addition to a broach, or toothed tool.
  • Rotary – – Examples of rotary cutting tools include cold saw blades, drill bits, milling cutters, countersinks, and taps and dies.

Some cutting tool technology can combine aspects of both linear and rotary cutting motion. These may include hacksaw or bandsaw blades and fly cutters.

There are two main constructions of tool engineering: those using inserts or solid cutting tools.

Tools with inserts

Replaceable tips or inserts are often incorporated into cutting tool solutions. A cutting tool with an insert will have a cutting edge that’s separate from the body. This cutting edge is then welded, clamped, or brazed onto the tool body itself. The material of a cutting tool must be harder than the material of the object being cut. The cutting edge must also be able to endure the high heat generated during the cutting process. As such, tips are often made of very strong material such as cemented carbide, cubic boron nitride, and polycrystalline diamond.

Examples of cutting tools that use inserts include endmills, fly cutters, saw blades, and tool bits.

Solid cutting tools for engineering

Some cutting tools are too small to use changeable inserts. Instead, these smaller cutting tools are made as a single, solid unit. Solid cutting tools have no changeable inserts. These cutting tools are used for drilling and milling. The cutting edge is built of the same material as the shank and the two are part of the same piece.

The design of a cutting tool

Whether they are a solid tool or one that uses an insert, cutting tools must be constructed in accordance with a very specific geometry. The cutting tool will need precise clearing angles so the edge can contact the object being cut without having the shank of the tool resting on the object’s surface. In addition, the angle of the cutting face and flute width are important considerations in designing or choosing a cutting tool. For the tool to be long-lasting, all of its features – – from the angles to the number of teeth and margin size – – must be optimized.

The importance of the cutting edge

As noted above, the cutting edge must be made of material strong enough to withstand the heat and abrasion of the cutting process. In selecting from the cutting tools available, ensure the cutting edge will meet your needs by looking at its:

  • Form – – that is, the trumpete, waterfall, or radius
  • Chamfers – – their form and size
  • Angles – – both the free angle and rake angle

A cutting edge is measured with a tactile instrument or one that uses focus variation. Focus variation uses an optics with a limited depth of field to determine the depth of a sharp image.

The material of the tool

There are two main types of material used in tooling manufacturing: stable and unstable.

Stable materials

As the name suggests, stable materials remain stable under the heat produced during the machining process. This is possible because stable materials aren’t hardened using heat during the manufacturing process.
In general, stable materials will break before they’ll flex. This can make them fragile and lead to wear over time. Regardless, these materials aren’t prone to changing their properties during use.

Unstable materials

Unstable materials are hardened using heat to encourage the growth of had particles. Because heat is used in the hardening process, these materials are unstable during cutting, when heat is produced.
Unlike stable materials, however, unstable materials are more flexible and will often give before breaking. Being softer makes them tougher and thus more suitable for less favorable machining conditions.

Choosing the right tool

From the type to the angle and the material of the tool, its important to select the one suited to your job specifications.

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