What Is Cutting Tool?
Cutting tools is a wedge-shaped and sharp-edged tool used to remove excess layers of material from a workpiece by shearing during machining to obtain the desired shape, size, and accuracy. It is firmly attached to the machine tool. A relative velocity between the workpiece and the cutting tool is also provided by various mechanical and other mechanisms for the cutting action.
It is tightly fixed on the machine tools. A relative velocity is also promoted to operate between the cutting tool and the workpiece by various mechanical arrangements to performs cutting action. The cutting material must be harder than the material to be cut, and the tool must withstand the heat & force generated during the machining process.
In addition, the tools must have a certain geometry, with clearances angles designed so that the cutting edge touches the workpiece without the rest of the tool piece on the workpiece surface. The cutting face angles are just as important as the width of the flute, the number of flutes or teeth, and the shape of the edge.
For longer service life, all of the above points, as well as the speed and feed at which the equipment operates, must be optimized. Cutting can be accomplished by single-point cutting tools or multi-point cutting tools. Let us move on to the subsequent sections to know about cutting tools, their types, and some practical examples.
Materials of Cutting Tool:
During machining, the cutting tool part remains in physical contact with the workpiece and thus experiences severe cutting temperatures and constant rubbing. The material of the cutting tools must have the ability to sustain such high cutting temperatures as well as cutting strength.
Each tool material must have certain properties such as high hardness, high hot hardness, high strength, high melting point, and chemically inert even at high cutting temperatures. As a thumbs rule, the hardness of the tool’s material should be at least 1.5 times the hardness of the workpiece for the smooth cutting action.
A suitable coating can also be applied to the equipment to improve various desired properties. However, a coated tool does not allow grinding and re-sharpening as easily as the edges wear out after prolonged use. Nowadays, insert-based tools are available where small interchangeable inserts can be attached or fastened to the larger shank.
These inserts act as cutting and thus gradually wear out. When wear exceeds the tolerable limit, the insert can be replaced with a new one, while the shank can be used repeatedly. Listed below are some of the tool materials commonly available in today’s market.
- High-Speed Steel (HSS)
- Tungsten carbide
- Cubic Boron Nitride (CBN)
Classification of Cutting Tools:
A cutting tool may consist of one or more prominent cutting edges that participate in the simultaneous cutting process in a single pass. The cutting tool can be classified in several ways; However, the most common method is based on the number of major cutting edges participating in the cutting process at the same time. On this basis, the cutting tool can be divided into three groups, as mentioned below.
#1. Single Points Cutting Tool
Single points cutting tool has only one main cutting edge that can remove material at once in a single pass. Single point cutting tool is used in turning, shaping, planning, and similar operations.
It is made from hard materials such as high carbons steel, high-speed steel, ceramic, & diamond. With a single-point cutting tool, because one cutting edge does all the work, there is a chance that the materials will not be removed very quickly, & the cutting edge is more likely to break.
If a cutting edge breaks during use, you must stop and replace the entire tool before using it again.
Single-point tools, such as a single-blade reamer, have only one cutting edge that removes materials.
Single-blade reamers often take longers because only one edge is worked. The main advantage of the single-point cutting tool is that the design and manufacture are much simpler and less time-consuming, & such tools are comparatively cheap.
Single cutting edge also has disadvantages; It is in constant contact with the workpieces during machining. As a result, tool wears are high, and tool life is shortened. Due to continuous contact, the rate of increase in equipment temperature is high.
On the one hand, this accelerates tools wear and, on the other hand, causes thermal damage to the finished surface. A high rise in temperature can deform the tooltip too much, which can lead to poor machining accuracy.
Since only one pass for a cutting edge requires the full depth of cut (chip load), the material removal rate (MRR) is very low. Thus, productivity is low.
#2. Double Point Cutting Tool
A double point cutting tool has two cutting edges that can cut or shear at the same time in a single operation. In contrast, a single-point cutting tool has only one main cutting edge. Multi-edge cutting tools have more than two cutting edges to perform machining operations in a single pass.
Sometimes cutters can simply be divided into two groups when double-point cutters are also considered multi-point cutters. In addition, cutting edges are obtained through the intersection of a rake face and a flank.
Therefore, double-point cutting tools have two rake faces and two flanks. Double Point Cutting Tool Example: The drill is the only example for this category. Note that the drill may have more than two cutting edges.
However, traditional without cutting edge modification metal cutting practice has two cutting edges. The simultaneous actions of two cutting edges sometimes produce a fixed cutting component in which the two cutting edges automatically eliminate (or reduce) each other. It reduces various shocks such as instability, vibration, etc., of unbalanced cutting force.
#3. Multi-Point Cutting Tools
A multi-point cutting tool has more than two main cutting edges that work together in one pass. Sometimes a cutter with two cutting edges is also seen as a multi-cutting tool instead of a double-point cutter.
The number of cutting edge presents in a multi-point cutter can vary from three to a few hundred. Unlike a single-point tool, a multi-point cutting tool allows more than one cutting edge to be used at the same time. Ultimately, the Multi-Point Tools allows multiple edges of the tool to extract material at once.
These allow multiple cutting tools or “multi-blade” tools to be run faster than single cutting tools. Because the amounts of heat generated at the cutting edges are distributed across each cutting blade, the tools can often last longer and be more wear-resistant. DiaTools High-Performance Reamer is a great example of multi-cutting tools.
Compared to alternatives methods, a multi-bladed reamer can shorten cycles times & increase quality. Multi-point cutting tool has many advantages, such as low chip load per tooths, high speed and feed, high MRR and productivity, low tool wear, low cutting temperature, and long tool life.
It also has disadvantages such as intermittents cuts, cutting edges, or teeth exposed to fluctuating loads. This creates noise, vibration, and permanents failure of the cutter. The cutter is comparatively difficult to design & manufacture. These make such cutters more expensive.
Types of Cutting Tools:
Cutting tools, as the name suggests, are used for cutting operations in machining techniques. Milling cutters can be used in a variety of machining applications. Therefore, milling cutters were named according to their respective role in machining.
Here is a list of commonly used cutting tools:
Single Point Turning Tool:- These cutting tools are for performing turning operations in a lathe machine.
Drill:- This cutter performs drilling operations and hence is attached to drilling, milling, or lathe machine.
Milling Cutter:- These tools are for performing milling operations on a milling machine.
Fly Cutter:- This tool performs the work of fly milling on the milling machine.
Shaper:- This cutter is meant to give specific shape and accuracy to the workpiece and is done on a shaping machine.
Planer:- This wedge device is similar to a shaper. However, in this process, larger workpieces are employed, which move during the process, whereas in shape, the cutter moves.
Boring Bar:- This cutting device is used on boring or drilling machines to carry out boring operations.
Reamer:- It is for performing reaming operations on the drilling machine.
Broach:- This cutting tool executes the broaching operation on the broaching machine.
Hob:- This cutter is used to perform hobbing operations on the hobbing machine.
Grinding Wheel:- This grinding tool is an abrasive tool that is used for grinding operation on a grinding machine.
Classification of Cutter Depending on the Shape:
Now, depending on the shapes of the cutter, the cutting tools are further differentiated. Let’s look at the category that cutting tools can be divided into according to size:
In general, this kind of cutter is employed as a lathe turning tool to perform the turning operation.
#2. Tipped Tool
These cutters were developed from different materials. That is, the body of the cutters is made of many different materials while its cutting part is developed from different materials. These two parts of the cutting tools can be joined by following any number of procedures, including clamping, welding, etc. Examples of the tool with tipping are tools with tungsten carbides tipping,
#5. Pointed Tool
As the name of the tools suggests, the teo of this cutter is sharp and fine. All the edges coincide in one line. Some examples of such cutting tools include hard carbide cutters and sharp diamonds mounted on the holder.
#4. Grain Size
They are cutting tools depending on the size of the grain and the number of grains. Assuming that the grain is small, this will remove more material from the workpiece. Conversely, if the grain size is large, more material will be cut off. For example, abrasive-type cutting tools are used in grinding wheels.
#3. Tool Bit
This is a non-rotating cutter. You can use this tool on shaping or planning machines to shape and plan the workpiece accordingly and much more.
It belongs to the category of cutting tools, which means that this cutting tool has only one main cutting groove. Some common examples of these types of cutting tools are cast non-ferrous satellite cobalt, lathe tool in machine holder, etc.