To achieve high-quality results in machining, selecting the right cutting tool is crucial.
The selection of cutting tools depends on the material properties of the workpiece and the desired outcome of the machining process.
The material properties of the workpiece are critical factors in tool selection. Harder materials require harder and more durable tool materials such as carbide or high-speed steel.
Softer materials, on the other hand, can be machined with tools made of less durable materials, such as high-carbon steel.
It is important to select a cutting tool made of a material that is harder than the material being machined to ensure the tool can withstand the forces involved in the machining process and maintain its cutting edge for a reasonable amount of time.
By considering the hardness of the workpiece, machinists can select a cutting tool that is best suited for the job at hand, minimizing tool wear and breakage and optimizing machining performance.
Toughness is a material property that refers to the ability of a material to resist fracture or failure due to the presence of cracks or other imperfections.
A material with high toughness can withstand high-stress situations without breaking or cracking.
Toughness is an important material property to consider when selecting a cutting tool. A tough material may require a tool with higher resistance to chipping, cracking, or breaking during the cutting process.
The cutting tool must be able to withstand the stress and impact of the machining operation without becoming damaged or deformed.
Ductility is an important property to consider when selecting cutting tools because materials with high ductility tend to deform instead of breaking when they are being machined.
This means that the cutting tool will need to be able to withstand the stresses generated during the machining process while maintaining a sharp cutting edge.
Ductility is also important when considering the surface finish of the machined part. When a material is machined, the deformation of the material at the surface of the part can affect the surface finish.
Materials with high ductility tend to deform more easily, which can lead to a smoother surface finish. However, materials that are too ductile may cause problems during machining, such as burrs or chips, which can negatively affect the final surface finish.
Work-hardening is the tendency of certain materials to harden or increase in strength when subjected to plastic deformation during machining.
During the machining process, the material is subjected to deformation as it is cut by the tool. If the material is prone to work-hardening, this deformation can cause the material to become harder and more difficult to cut as the machining process continues.
In order to machine work-hardening materials successfully, it may be necessary to use a cutting tool made of a harder and more wear-resistant material.
Cutting speeds and feed rates may also need to be adjusted to minimize the amount of work-hardening that occurs during machining.
Cutting speed is an important factor in tool selection because it affects the heat generated during machining, as well as the tool wear and deformation.
Higher cutting speeds require harder and more durable tools. This is because as the cutting speed increases, the temperature of the cutting tool and the workpiece also increases, which can cause the tool to wear more quickly.
The cutting speed is influenced by several factors, including the type of material being machined, the desired surface finish, and the machining process being used.
By selecting the appropriate cutting speed, machinists can optimize machining performance, improve surface finish, and minimize tool wear and breakage.
A higher feed rate can generate more heat due to increased friction between the cutting tool and the workpiece material. This can cause tool wear and deformation, resulting in poor surface finish, dimensional inaccuracies, and even tool breakage.
On the other hand, a slower feed rate can reduce heat buildup and improve cutting tool life, but it can also slow down the machining process and reduce productivity.
The optimal feed rate depends on several factors, including the material properties of the workpiece, the type of cutting tool, the cutting speed, and the desired surface finish.
When a cutting tool is in contact with the workpiece, it removes material by cutting a chip. The chip must be removed from the cutting zone to prevent damage to the tool or the workpiece.
In cutting operations such as turning, the chip is formed continuously, and it is typically curled around the tool's cutting edge.
In these operations, chip breaking is essential to prevent the chip from wrapping around the workpiece or the tool, which can cause damage or result in poor surface finish. The design of the cutting tool and the selection of the proper feed and speed rates can affect chip formation and breakage.
During cutting operations that are interrupted, such as drilling, the chip is formed in discrete segments. The design of the drill bit must be able to break the chips into small pieces and remove them from the hole.
Inadequate chip removal can cause clogging, tool wear, and poor hole quality.
Machining process refers to a broad range of manufacturing techniques used to remove material from a workpiece to create the desired shape, size, and surface finish.
The most common machining processes include turning, milling and drilling. Each process requires a specific type of cutting tool with a particular geometry, coating, and other features to achieve optimal results.
The selection of these factors depends on the specific requirements of the machining process, such as the type of material, the required tolerances, and the desired surface finish.
Machining capability refers to the ability of the machining equipment to perform the required operations accurately and efficiently.
The capability of the machine tool depends on several factors, including the type of machine, its size, power and precision.
The selection of the cutting tool must consider the capability of the machine tool to perform the desired operation. If the machine tool does not have the power to handle a particular cutting tool or if its rigidity is insufficient, it may not be possible to achieve the required results.
It is also essential to consider the machining capability of the equipment when selecting the cutting tool. The tool's size, shape, and geometry should be compatible with the machine's spindle, tool holder, and other accessories
Surface finish refers to the final texture and appearance of a machined surface.
It is an important consideration in machining operations, as it can affect the function, aesthetics, and durability of the finished product. The desired surface finish can vary depending on the application, and may range from a rough, textured surface to a mirror-like polished finish.
The choice of cutting tool, cutting parameters, and machining technique can all affect the surface finish. A rough surface may be desirable for certain applications, such as for better adhesion of paint or coatings.
A smooth and polished surface may be preferred for applications that require minimal friction, such as in bearings or sliding surfaces.
Achieving the desired surface finish requires careful selection of cutting tools, appropriate machining parameters (such as cutting speed, feed rate, and depth of cut), and proper machining techniques.
Tolerance refers to the acceptable range of deviation from a specified dimension or measurement of a workpiece. It is the difference between the maximum and minimum limits of a specified dimension.
In machining operations, parts must be manufactured to precise tolerances to ensure that they meet the required specifications.
The required tolerance depends on the application and the functional requirements of the part.
Tighter tolerances require more precise machining, which can affect tool selection, machining process, and cost.
The tolerance of the final dimensions of the workpiece can also be affected by other factors, such as the material properties, cutting tools, machining parameters, and environmental conditions.
Machining to tighter tolerances may require more precise machining equipment and higher precision cutting tools, which can increase the cost of the machining process.
Volume refers to the quantity of parts that need to be produced. The volume of production is an important consideration in tool selection because it can influence the choice of tool materials and the tool's wear resistance.
If a large volume of parts needs to be produced, then a tool that can withstand high production rates and has a longer life will be more suitable.
However if only a small volume of parts is required, a less durable tool may be sufficient, and the cost of the tool may be a more significant consideration.
Coolant is a liquid or gas that is used in machining operations to reduce heat generated by friction and remove chips from the cutting zone. Coolant helps to prolong tool life, improve surface finish, and prevent workpiece deformation or warping.
There are several types of coolants, including water-based, oil-based, and synthetic-based.
The choice of coolant depends on several factors, including the type of material being machined, the cutting tool being used, and the machining process.
Water-based coolants are typically used for low-speed machining operations, while oil-based coolants are used for high-speed machining operations.
Synthetic-based coolants are often used in high-precision machining operations that require excellent surface finish and dimensional accuracy.
The machining environment is an important factor to consider when selecting a cutting tool. Temperature, humidity, and dust levels can all impact the performance of the tool and the quality of the finished product.
High temperatures can cause tools to wear out more quickly, while high humidity can lead to rust and corrosion. Dust levels can also affect tool performance, as excessive dust can clog the cutting edge and reduce cutting efficiency.
To ensure optimal tool performance, it is important to choose a cutting tool that is suitable for the specific machining environment, if the environment is particularly dusty, a tool with a coating that resists clogging may be a good choice.
If the environment is particularly humid, a tool with corrosion-resistant properties may be preferred.