Advanced Milling/Turning
This page is dedicated to the theory of units 010 and 009
Units:
AME3-010 Turning
AME3-009 Milling
Milling Machine
Lathe
Common types of lathes:
Watchmakers, toolroom, general purpose, heavy duty, roll turning,
Materials used in tooling
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The cheapest of the bunch. And this is exactly why it still finds use. As carbon steel is not very durable, it is only suitable for low-speed operations.
Carbon steel loses its hardness at 200° C. This is the reason for lower speeds – to keep the heating effect low.
Materials Carbon Steel can cut: Mild steel, Stainless steel, Cast iron, “Soft” Non-ferrous metals (Brass, Copper)
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High-speed steel, a grade of tool steels, has a few alloying elements added to it to provide better response to heat and wear than regular carbon steel. While the life cycle of such a tool goes up, so does the cost.
High-speed steel loses its hardness at 600° C. Therefore, higher milling speeds are suitable for these tool steels.
Materials HSS can cut: Steel, Cast iron, Non-ferrous metals, Plastics. (Some composites and ceramics)
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A cermet is a composite material consisting of ceramic (cer) and metallic (met) materials. The ceramic in general has high temperature resistance and hardness, and the metal has the ability to undergo plastic deformation. A cermet is ideally designed to have the combined optimal properties of a ceramic and a metal.
This material is harder than high-speed steel but the toughness qualities are not that impressive. The higher hardness provides better protection against wear but lower toughness levels make it a little more susceptible to cracking and chipping.
The upper temperature of use is at 900° C.
Material cermet tools can cut: Steel, Stainless steel, Cast iron, Non-ferrous metals, Hardened materials, Heat resistant alloys (Inconel and titanium)
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Cutting ceramics are even harder than cemented carbides but lose in the toughness aspect. Both aluminium oxide and silicon nitride are used to produce these tools with varying properties.
Cutting ceramic tools are prone to cracking when used on hard materials and with high temperatures. Therefore, they are not really suitable for machining steels, for example. Otherwise, a short tool life is to be expected.
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CBN (cubic boron nitride) and diamond cutting tools are a type of cutting tool that uses either CBN or diamond as the cutting material. These cutting tools are known for their high hardness, wear resistance, and thermal stability, making them ideal for cutting very hard and abrasive materials.
CBN cutting tools are made by sintering CBN grains with a metal binder, typically cobalt. The resulting tool has a high degree of hardness and toughness, which allows it to cut materials such as hardened steel, cast iron, and superalloys. CBN tools are also capable of high-speed cutting, which can result in increased productivity.
Diamond cutting tools, on the other hand, use synthetic diamond as the cutting material. These tools are made by either brazing diamond grit onto a tool substrate or by sintering diamond particles with a metal binder, such as cobalt or tungsten carbide. Diamond tools are very hard and can cut a wide range of materials, including ceramics, composites, and non-ferrous metals.
CBN and diamond cutting tools are used in a variety of applications, including aerospace, automotive, and medical industries, where materials are often very hard and difficult to machine. These tools are particularly useful for machining high-value and critical components, as they can produce high-quality surface finishes and tolerances. However, due to their high cost, they are typically reserved for high-volume or specialized applications.
“Coated” Tools
Cutting tools are commonly found with an ultra-thin molecular compound coating applied to its cutting surfaces. These coatings are engineered to combat against forces that wear down your cutting tools and lead to catastrophic tool failure. Not only are coatings created for cutting specific materials, but they also limit heat and friction and enhance the performance of your tool.
When selecting a coated tool, the machinist must consider how the material and desired cutting operations may break down the cutting edges of the tool, to determine which coating will best serve their needs. Before those decisions can be made, one must understand how coatings increase a tool’s cutting abilities.
Real life examples of the benefits from coatings.
Types of coatings
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This coating is a popular choice for general-purpose cutting tools, as it provides a good balance of wear resistance and low friction.
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This coating provides improved wear resistance and toughness compared to TiN and is a good choice for cutting tough materials.
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This coating provides excellent wear resistance and toughness and is a good choice for cutting difficult-to-machine materials.
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This coating provides similar performance to TiAlN but has improved adhesion properties.
The benefits of coating
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Heat mitigation is essential in machining, as excessive tool and workpiece heating during cutting operations can be detrimental. As the carbide tool’s temperature rapidly increases, its hardness decreases, resulting in greater wear and burn out. Thermal conductivity is a material property used to measure a material’s ability to retain or transfer heat energy. For example, tungsten carbide has a thermal conductivity of 88 W/m.K at 20°C. This means at room temperature, 20°C (68°F), an uncoated carbide tool can conduct 88 Watts of thermal energy per meter with a temperature gradient measured in Kelvin. The materials used in tool coatings do not conduct heat as well with thermal conductivity rates as low as 4.5 W/m.K. This means that a coating with a thermal conductivity of 4.5 W/m.K, the coating would transfer 19.56 times less heat than tungsten carbide.
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Another key to limiting heat generation and keeping cutting smooth and chatter-free is to decrease the amount of friction between the cutting tool and workpiece. Frictional force is the resistance to motion, and in the case of cutting tools, the force opposing the lateral and radial movements of the tools as it cuts through the workpiece. This opposing force is determined by the coefficient of friction, often denoted as the Greek letter Mu (μ). The friction coefficient is the ratio between the force required to move one surface across another, divided by the pressure between the two surfaces. Minimizing μ is how coatings decrease the overall frictional forces involved in cutting operations because the force of friction is directly proportional to μ.
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Adding a coating with a high microhardness rating increases a cutting tool’s ability to resist wear and avoid permanent deformations. In the cutting industry, cutting tool grades for tungsten carbide range from grades C1 to C14, depending on what the cutting operation the tool will be performing. Between grades C1 to C14, tungsten carbide has a Vickers Hardness (HV) ranging from 760 HV to 1740 HV. Tool coatings have higher microhardness ratings than tungsten carbide. Adding a coating can increase a tool’s hardness anywhere from 2213 HV using a TiN coating, to 9993 HV with the CVD diamond coating. While a TiN coating would not be chosen solely for its hardness, it shows that even the coating with the lowest hardness is still harder than bare tungsten carbide. By making the cutting tool significantly harder, the ratio of workpiece hardness to tool hardness increases. Increasing the tool’s hardness will allow it to shear off chips and remove material with greater ease, especially against high abrasive materials, while the tool maintains its structural integrity against the extreme forces experienced during cutting operations.
Coated milling tools
The importance of drill speeds, and how to select them
This Sway to the right is a lesson I previously made on how why speed selection for drilling is important and how we workout what speed to pick.
Quick Summary
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Cutting Speed: Vc= (pi x D x n) / 1000
Spindle speed: n = Vc / pi / D x 1000
Vc = Cutting Speed
pi = 3.14
D = Diameter (mm)
n = Spindle speed
For Vc you will most likely need to refer to a cutting speed chart to get this number
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P = Steels
M = Stainless Steel
K = Cast Iron
N = Non-ferrous Materials
S= Super Alloys
H = High Temp Alloys
Material machining terminology
“Machineability”
Machineability refers to the ability of a material to be easily and efficiently machined using a lathe. This includes factors such as the ease of cutting the material, the amount of tool wear, the surface finish that can be achieved, and the overall productivity of the machining process.
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The machineability of a material is influenced by various factors, including its chemical composition, microstructure, and mechanical properties. Materials that are considered highly machineable are typically soft and ductile, with low levels of internal stress and good chip-breaking properties. Examples of highly machineable materials include low-carbon steels, brass, and aluminum.
On the other hand, materials that are difficult to machine are typically harder, more brittle, or have a tendency to work-harden during machining. These materials can lead to excessive tool wear, poor surface finish, and reduced productivity. Examples of materials that are difficult to machine include hardened steels, titanium alloys, and some types of ceramics.
In general, the machineability of a material is an important consideration when selecting materials for lathe work, as it can have a significant impact on the efficiency and quality of the machining process.
“Annealing”
Annealing is a heat treatment process used to soften and improve the machinability of a metal. Annealing involves heating a metal to a specific temperature and holding it at that temperature for a period of time, before cooling it slowly to room temperature. This process causes the metal's internal structure to become more uniform, with fewer defects such as dislocations and voids. The resulting metal is softer, more ductile, and easier to machine, with improved surface finish and reduced tool wear. Annealing can also relieve internal stresses in the metal, which can improve its dimensional stability and reduce the likelihood of cracking or distortion during machining. The specific temperature and time required for annealing will depend on the type of metal being treated and its initial condition, and can be determined through experimentation or reference to established guidelines.
“Free cutting”
The term "free cutting" refers to materials that are easy to machine and produce minimal wear on the cutting tools. This allows for faster machining speeds, increased productivity, and improved surface finish.
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Free cutting materials are typically alloys that have been specifically designed to optimize machinability. These alloys typically have high levels of sulfur, lead, or other elements that act as lubricants and reduce friction between the cutting tool and the workpiece. As a result, the chips produced during machining break off cleanly and easily, without forming long, stringy chips that can cause problems during machining.
Examples of free cutting materials include brass, aluminum, low-carbon steels, and some types of stainless steel. These materials are commonly used in applications where high productivity and good surface finish are important, such as in the manufacture of automotive components, plumbing fixtures, and electronic connectors.
It is important to note that while free cutting materials offer advantages in terms of machining efficiency, they may not always be the best choice for all applications. For example, materials that contain high levels of lead or sulfur may be unsuitable for use in environments where contamination or health hazards are a concern. Additionally, some free cutting materials may have reduced mechanical properties, which may limit their use in applications where high strength or durability are required.
“Structure”
Structure generally refers to the arrangement of the atoms or molecules that make up a material. The structure of a material can have a significant impact on its properties, including its mechanical strength, hardness, ductility, and machinability.
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There are several factors that can influence the structure of a material, including its chemical composition, the processing methods used to create the material, and the conditions under which it is processed or used. For example, heat treatment can be used to modify the structure of a material by changing the arrangement of its atoms or molecules, which can in turn affect its mechanical and thermal properties.
In lathe work, the structure of a material can have a significant impact on its machinability. Materials with a fine, uniform structure are generally easier to machine than materials with a more coarse or irregular structure. This is because a fine structure allows for a more consistent and predictable response to cutting forces, resulting in smoother cuts and better surface finish.
However, the optimal structure for a given application will depend on a variety of factors, including the specific properties required for the part being machined, the machining process being used, and the materials being used. For example, materials with a very fine structure may be more susceptible to work hardening during machining, which can reduce their machinability and require adjustments to the machining process.
In summary, the structure of a material is an important consideration in lathe work, as it can have a significant impact on the efficiency and quality of the machining process. Machinists must carefully select materials with the appropriate structure for their specific application, and may need to adjust their machining techniques to optimize performance based on the material's structure.
“Normalised”
In lathe work, normalizing is a heat treatment process used to improve the mechanical properties of a metal. Normalizing involves heating a metal to a specific temperature and holding it at that temperature for a period of time, before cooling it in still air. This process causes the metal's internal structure to become more uniform, with smaller grain size and improved toughness, strength, and ductility. Normalizing can also refine the microstructure of a metal, making it more suitable for subsequent machining or forming operations. The specific temperature and time required for normalizing will depend on the type of metal being treated and its initial condition, and can be determined through experimentation or reference to established guidelines. Normalizing is often used to prepare a metal for further heat treatment or machining, and can be an important step in the production of high-quality machine parts.
“Alloying”
Alloying refers to the process of combining two or more metallic elements to create a material with specific properties that are desirable for a particular application. Alloying can be used to enhance properties such as strength, hardness, corrosion resistance, and machinability.
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Alloying can be achieved by melting the constituent metals together and allowing them to solidify, or by mechanically mixing the metals in powder form and then compacting and sintering the mixture. The resulting alloy will often have properties that are different from those of the individual metals used to make it.
The choice of alloying elements and their proportions can be tailored to achieve specific properties. For example, adding small amounts of carbon to iron can create steel, which is much stronger than pure iron. Adding chromium to steel can greatly enhance its corrosion resistance, making it suitable for use in harsh environments.
Alloying can also be used to improve the machinability of materials. For example, adding lead or sulfur to steel can create "free cutting" alloys that are much easier to machine than regular steel. Similarly, adding aluminium to copper can create an alloy with improved machinability, known as aluminium bronze.
Overall, alloying is a powerful tool for creating materials with tailored properties to meet the specific needs of different applications, including those that involve lathe work.
“Hardening”
Hardening is a heat treatment process used to increase the hardness and strength of a metal. Hardening involves heating a metal to a high temperature and then rapidly cooling it, usually by quenching it in a liquid such as water or oil. This rapid cooling process causes the metal's internal structure to transform from a soft, ductile state to a hard, brittle state, with a more uniform and finely distributed microstructure. Hardening can significantly improve the wear resistance and durability of a metal, making it suitable for use in applications that require high strength and toughness, such as cutting tools or machine components subjected to heavy loads or wear. However, hardened metals can also be more difficult to machine, as they are more prone to cracking, chipping, or other forms of damage. Machinists must carefully select cutting tools and machining parameters to ensure that hardened materials are machined with the appropriate precision and surface finish. The specific temperature and cooling method used for hardening will depend on the type of metal being treated and the desired properties, and can be determined through experimentation or reference to established guidelines.
Hardness Testing
Hardness testing is a way of measuring the resistance of a material to deformation, particularly plastic deformation or indentation. It is an important method of assessing the properties of materials, particularly metals, and alloys, but it can also be used for other materials such as ceramics, polymers, and composites.
There are several methods of hardness testing, but most of them involve pressing or indenting a small indenter or probe into the surface of the material and measuring the resulting indentation. The depth or size of the indentation is then used to calculate the hardness of the material.
Some common hardness testing methods include Rockwell hardness testing, Brinell hardness testing, and Vickers hardness testing. Each method has its own specific procedure and equipment, but they all aim to provide a measure of the material's hardness and related properties such as strength, ductility, and toughness.
Hardness testing is an important tool in material science, engineering, manufacturing, and quality control, as it can help to ensure that materials meet certain specifications and standards for specific applications.
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There are different types of hardness testing because different materials have different properties, and the way these properties are measured and expressed can vary. Therefore, different hardness testing methods are used to accommodate these differences and provide accurate measurements of hardness.
Different hardness testing methods are also used because they have different strengths and limitations. For example, some methods may be better suited for measuring the hardness of very hard materials, while others may be better suited for measuring the hardness of softer materials. Some methods may be faster and easier to perform, while others may be more precise and accurate.
Another reason for different hardness testing methods is that different industries and applications may have different standards and requirements for hardness measurements. For example, the automotive industry may require a specific type of hardness testing for certain parts, while the aerospace industry may require a different type of hardness testing for different components.
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Vickers hardness is a method of hardness testing that uses a diamond-shaped indenter to measure the resistance of a material to indentation. The Vickers hardness test is based on the measurement of the diagonals of the indentation left by the indenter on the surface of the material being tested.
The Vickers hardness test is widely used in the testing of materials, particularly metals and ceramics, because it is simple to perform, produces accurate results, and can be used to measure a wide range of material hardnesses. The test can be performed on materials ranging from very soft to extremely hard.
The Vickers hardness number is calculated by dividing the load applied to the material during the test by the surface area of the indentation. The resulting value is a measure of the material's resistance to indentation and is expressed in units of pressure (such as kgf/mm²).
Overall, the Vickers hardness test is a versatile and widely used method of hardness testing that can provide important information about the properties of materials in various industries and applications.
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Brinell hardness is a method of hardness testing that uses a spherical indenter to measure the resistance of a material to indentation. The Brinell hardness test is based on the measurement of the diameter of the indentation left by the indenter on the surface of the material being tested.
The Brinell hardness test is commonly used in the testing of metals and alloys, particularly those with coarse microstructures or uneven surfaces. It is also used in the testing of materials that are too large or irregularly shaped to be tested using other hardness testing methods.
During the Brinell hardness test, a load is applied to the material being tested, causing the spherical indenter to indent the surface of the material. The diameter of the resulting indentation is then measured using a microscope or other measuring device. The Brinell hardness number is calculated by dividing the load applied to the material during the test by the surface area of the indentation. The resulting value is a measure of the material's resistance to indentation and is expressed in units of pressure (such as kgf/mm²).
To summarize, the Brinell hardness test is a useful method of hardness testing for materials with coarse microstructures or uneven surfaces. It is a simple and reliable test that can provide important information about the properties of metals and alloys in various industries and applications.
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Rockwell hardness is a method of hardness testing that uses a diamond or ball-shaped indenter to measure the resistance of a material to indentation. The Rockwell hardness test is based on the measurement of the depth of the indentation left by the indenter on the surface of the material being tested.
The Rockwell hardness test is widely used in the testing of metals and alloys because it is simple to perform, produces quick and accurate results, and can be used to measure a wide range of material hardnesses. The test can be performed on materials ranging from very soft to extremely hard.
The Rockwell hardness number is calculated by measuring the depth of the indentation left by the indenter after applying a minor load and then a major load. The difference between the depth of the indentation with the major load and the depth of the indentation with the minor load is used to calculate the Rockwell hardness number, which is expressed as a scale number (such as HRC, HRB, or HRA).
Rockwell hardness is a versatile and widely used method of hardness testing that can provide important information about the properties of metals and alloys in various industries and applications. It is particularly useful for testing small or thin samples, and for measuring the hardness of heat-treated materials.
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Shore hardness is a method of measuring the hardness of polymers, elastomers, and other materials that are soft or flexible. The Shore hardness test is based on the measurement of the resistance of the material to indentation by a sharp-pointed indenter.
The Shore hardness test measures the depth of indentation left by a spring-loaded indenter with a specific geometry, typically a cone or a ball. The indenter is pressed into the surface of the material under a fixed load, and the depth of the indentation is measured.
There are two main scales for Shore hardness testing: Shore A and Shore D. Shore A is used for measuring the hardness of softer materials such as rubber and plastics, while Shore D is used for harder materials such as rigid plastics and hard rubber.
The Shore hardness number is calculated based on the depth of the indentation and is expressed as a dimensionless number on the Shore A or Shore D scale. Higher Shore hardness numbers indicate harder materials, while lower numbers indicate softer materials.
Shore hardness testing is widely used in the rubber and plastics industries, as well as in other industries where the hardness of soft or flexible materials needs to be measured. It is a simple and quick method of hardness testing that can provide important information about the properties of materials in various applications.
Procedures for Milling
Methods of manufacturing and how they influence material structure
How the metal stock is produced can affect the ways we should machine them.
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Cast metals can have a significant effect on turning operations, depending on the specific properties of the metal and the type of turning process being used. Here are some general ways that cast metal can affect turning:
Hardness: Cast metals can have varying levels of hardness, which can make them more or less difficult to turn. Harder cast metals can be more challenging to cut and may require special tooling or cutting techniques to achieve the desired result.
Inclusions: Cast metals may contain inclusions, such as bubbles or impurities, that can affect the consistency of the material being turned. Inclusions can cause unexpected variations in the surface finish or dimensional accuracy of the part being turned.
Grain structure: The grain structure of cast metal can vary depending on the casting process used. This can affect how the metal behaves during turning, including how it responds to cutting forces and the likelihood of cracking or other types of damage.
Surface finish: The surface finish of a cast metal part can impact the turning process. Rough or uneven surfaces can cause chatter or vibration during turning, which can lead to poor surface finish or even damage to the cutting tool.
Overall, it is important to consider the specific properties of the cast metal being turned when planning and executing a turning operation. This may involve selecting appropriate cutting tools and techniques, as well as monitoring the process closely to ensure consistent and accurate results.
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Forged metal can also have an impact on turning operations, but the specific effects will depend on the type of metal being forged and the forging process used. Here are some general ways that forged metal can affect turning:
Grain structure: Forged metals generally have a more uniform grain structure compared to cast metals, which can make them easier to turn. The uniformity of the grain structure can result in more consistent cutting forces and improved surface finish.
Hardness: Forged metals can be harder than their cast counterparts, which can make them more challenging to turn. Hardness can also vary depending on the specific alloy and forging process used.
Residual stresses: Forging can introduce residual stresses into the metal, which can affect the material's behavior during turning. Residual stresses can cause the metal to deform or move during the turning process, leading to dimensional inaccuracies or other issues.
Surface finish: The surface finish of a forged metal part can also affect turning operations. Rough or uneven surfaces can cause chatter or vibration during turning, leading to poor surface finish or even damage to the cutting tool.
As with cast metals, it is important to consider the specific properties of the forged metal being turned and select appropriate cutting tools and techniques. Monitoring the turning process closely can also help ensure consistent and accurate results.
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Rolled metal can have an impact on turning operations, but again the specific effects will depend on the type of metal being rolled and the rolling process used. Here are some general ways that rolled metal can affect turning:
Grain structure: Rolled metals can have a more uniform and refined grain structure compared to cast metals, which can make them easier to turn. The uniformity of the grain structure can result in more consistent cutting forces and improved surface finish.
Hardness: Rolled metals can be harder than their cast counterparts, which can make them more challenging to turn. Hardness can also vary depending on the specific alloy and rolling process used.
Residual stresses: Rolling can introduce residual stresses into the metal, which can affect the material's behavior during turning. Residual stresses can cause the metal to deform or move during the turning process, leading to dimensional inaccuracies or other issues.
Surface finish: The surface finish of a rolled metal part can also affect turning operations. Rough or uneven surfaces can cause chatter or vibration during turning, leading to poor surface finish or even damage to the cutting tool.
As with cast and forged metals, it is important to consider the specific properties of the rolled metal being turned and select appropriate cutting tools and techniques. Monitoring the turning process closely can also help ensure consistent and accurate results.
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Sintered metal can also have an impact on turning operations, but the specific effects will depend on the type of metal being sintered and the sintering process used. Here are some general ways that sintered metal can affect turning:
Density: Sintered metals can have a high density, which can make them more difficult to turn. The high density can result in higher cutting forces and may require more robust cutting tools or techniques.
Porosity: Sintered metals can also have a porous structure, which can affect the material's behavior during turning. The porosity can cause the metal to deform or move during the turning process, leading to dimensional inaccuracies or other issues.
Hardness: Sintered metals can vary in hardness depending on the specific material and sintering process used. Some sintered metals can be harder than their cast or forged counterparts, which can make them more challenging to turn.
Surface finish: The surface finish of a sintered metal part can also affect turning operations. Rough or uneven surfaces can cause chatter or vibration during turning, leading to poor surface finish or even damage to the cutting tool.
As with other metal types, it is important to consider the specific properties of the sintered metal being turned and select appropriate cutting tools and techniques. Monitoring the turning process closely can also help ensure consistent and accurate results.
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In general, metal extrusion does not have a direct impact on lathe work. However, the quality of the extruded material, such as its dimensional accuracy, surface finish, and metallurgical properties, can affect the quality of the final machined product. Poor quality extruded material can lead to difficulties in machining, such as tool wear or poor surface finish, which can impact the overall quality and cost-effectiveness of the lathe work.
How does the presence of common elements affect the machineability of metals
The presence of common elements can have both positive and negative effects on the machinability of metals. Some common elements that can have an impact on machinability include carbon, sulfur, phosphorus, and manganese.
Carbon is commonly added to steel to improve its strength, but high levels of carbon can make the metal more difficult to machine due to increased hardness and reduced ductility. Sulfur and phosphorus are often found in low-carbon steels as impurities, and their presence can lead to the formation of brittle compounds that can cause cracking and other issues during machining.
On the other hand, manganese is commonly added to steel as an alloying element, and it can improve machinability by increasing the metal's strength and reducing its tendency to work harden. Additionally, manganese can help reduce the formation of harmful compounds during machining.
The presence of common elements in metals can have a significant impact on machinability, and it is important for manufacturers to carefully consider the composition of their materials when selecting a metal for a particular machining application.
The impact of other elements
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Aluminum has good machinability, but the addition of elements such as silicon, magnesium, and copper can increase its strength and hardness, making it more difficult to machine. However, small amounts of these elements can also improve the surface finish of machined parts.
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Copper alloys can have good machinability, but the addition of elements such as lead, sulfur, and tellurium can improve chip formation and reduce tool wear. However, these elements can also reduce the strength and ductility of the metal.
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Nickel alloys can be difficult to machine due to their high strength and hardness, but the addition of elements such as sulfur, phosphorus, and selenium can improve machinability by reducing work hardening and improving chip formation.
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Titanium and titanium alloys are notoriously difficult to machine due to their high strength, low thermal conductivity, and tendency to work harden. However, the addition of elements such as aluminum, vanadium, and molybdenum can improve machinability by reducing the risk of tool chatter and improving chip formation.
Climb and Conventional Milling
Climb milling and conventional milling are two different methods of cutting metal during a milling operation. The main difference between them is the direction of the cutting forces that are exerted on the workpiece.
Climb milling, also known as down milling, the cutter rotates in the same direction as the feed, which means the cutting forces tend to pull the workpiece towards the cutter. This can result in smoother cuts and better surface finishes. Climb milling is generally used for finishing cuts and when the workpiece is held securely.
Straddle milling refers to using 2 cutters of the same size and cutting to slots of into a part parallel to each other
Conventional milling, also known as up milling, the cutter rotates against the direction of the feed, which means the cutting forces push the workpiece away from the cutter. This can result in a tendency for the workpiece to lift, chatter, or vibrate, which can lead to poor surface finish and reduced tool life. Conventional milling is generally used for roughing cuts and when the workpiece is not held securely.
Overall, climb milling is generally considered to be the preferred method when possible, as it can produce smoother finishes and is less likely to cause workpiece lift or chatter. However, the choice between climb milling and conventional milling ultimately depends on the specific application and the requirements of the workpiece being machined.
Chip and Dust management
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Flood coolant is a type of coolant system that delivers a stream of coolant to the cutting zone during machining processes. There are several benefits of using flood coolant when machining:
Increased tool life: Flood coolant can help to cool the cutting tool, reducing the amount of heat generated during machining. This can result in a longer tool life and reduced tool wear.
Improved surface finish: The use of flood coolant can help to flush away chips and debris from the cutting zone, preventing them from scratching the workpiece and resulting in a smoother surface finish.
Improved chip control: Flood coolant can help to break up chips and remove them from the cutting zone, reducing the likelihood of chip recutting and resulting in more efficient chip evacuation.
Reduced thermal distortion: By keeping the cutting zone cool, flood coolant can help to reduce thermal distortion in the workpiece, resulting in more accurate machining.
Increased productivity: The use of flood coolant can allow for higher cutting speeds and feed rates, resulting in increased productivity and reduced machining time.
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Dust extraction is important to dust management when machining because it can help to remove harmful dust particles from the air, creating a safer and healthier working environment for machinists.
When machining, a variety of dust particles can be generated, including metal shavings, and abrasive dust. These particles can be harmful if inhaled, leading to respiratory issues and other health problems. Additionally, these particles can accumulate on machines and floors, creating a fire hazard.
By using a dust extraction system, these harmful particles can be captured and removed from the air, improving air quality in the machining environment. This not only protects the health of machinists, but can also improve productivity by reducing the amount of time required for cleaning and maintenance.
Dust extraction systems can be designed to meet the specific needs of a machining operation, and can include features such as hoods, ducting, filters, and fans. Proper maintenance and cleaning of the system is important to ensure that it is working effectively and efficiently.
Dust extraction is an important part of dust management when machining, helping to create a safer and healthier working environment for machinists while improving productivity and reducing the risk of fire hazards.
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RPE (Respiratory Protective Equipment) and PPE (Personal Protective Equipment) can both help machinists deal with chips and dust generated during machining.
RPE is designed to protect the respiratory system by filtering out airborne particles, such as dust and fumes. A variety of RPE options are available, including disposable masks, half-face masks, full-face masks, and powered air-purifying respirators (PAPRs). When properly used, RPE can reduce the inhalation of harmful dust and fumes, protecting the respiratory system and overall health of the machinist.
PPE, on the other hand, refers to equipment that is worn on the body to protect against physical hazards, such as chips, sparks, and other debris. Examples of PPE used in machining include safety glasses or face shields to protect the eyes, gloves to protect the hands, and aprons or jackets to protect clothing. By wearing appropriate PPE, machinists can reduce the risk of injury from flying chips and debris.
It is important to note that RPE and PPE are not substitutes for proper dust and chip management. These protective measures should be used in combination with other strategies, such as dust extraction and ventilation, to effectively manage the hazards associated with machining
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Slideway protection is a type of protective cover designed to protect the ways (or guide rails) of machine tools from chips, dust, and other contaminants. The ways of a machine tool are essential components that guide the movement of the cutting tool or workpiece, and damage or wear to these ways can result in reduced accuracy and increased maintenance costs.
Slideway protection can take several forms, including telescopic covers, bellows covers, and roll-up covers. These covers are typically made from a flexible material, such as nylon, PVC, or rubber, and are designed to enclose the ways of the machine tool. They can be customized to fit the specific dimensions and movement requirements of the machine tool, providing a barrier against chips, dust, and other contaminants.
By protecting the ways of the machine tool, slideway protection can help to reduce the amount of maintenance required, prolong the lifespan of the machine, and maintain its accuracy and performance over time. Slideway protection can also help to reduce the risk of damage to other components of the machine tool, such as the spindle and bearings, which can be affected by the presence of chips and debris.
Overall, slideway protection is an important component of machine tool maintenance and can help to protect machines from chips and dust by creating a barrier against contaminants that can cause damage and reduce accuracy.
Rotary tables and dividing heads
A Rotary table
Form turning is one of the simplest taper-turning processes on a lathe machine to produce a short taper. This method is shown in the taper diagram. At the required angle, the form is grounded. The tool is fed perpendicular to the lathe axis when the workpiece rotates.
A Dividing head
Direct and index milling
Setting up a rotary table.
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Ensure the rotary table and machine surface are free of debris, chips, or other contaminants that could affect accuracy.
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Securely mount the rotary table onto the machine table or other fixture. Assess the lift before undertaking, Rotary tables can be heavy and awkward.
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Rotate the rotary table to the desired position and use an indicator to align it with the spindle.
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Before machining, check for clearance between the workpiece, cutting tool, and any other machine components to avoid collisions or damage.
Rotary Table uses:
Machine spanner flats on a bolt
Drill equidistant holes on a circular flange
Cut a round piece with a protruding tang
Dividing heads
Dividing heads are closely related to the rotary table, they are a type of work-holding device that allows the user to “index work” and cut complex shapes. They have many uses and can have many holding devices.
3 jaw chucks
4 jaw chucks
Arbors
Collets
Gear cutting: The dividing head is often used to cut gears. The gear blank is mounted on the dividing head, and the cutter is held stationary. The workpiece is rotated, and the cutter is fed into the workpiece to cut the teeth.
Spiral Milling
The maths of dividing heads
To cut complex curves
To cut straight lines at any angle
To cut arcs
Indexing: The dividing head is used to divide a workpiece into a specific number of equally spaced parts. The workpiece is rotated by the dividing head, and the indexing plate is used to lock the workpiece at precise intervals.
Spiral milling with a dividing head is a machining process used to produce helical or spiral features on a workpiece using a dividing head and a milling machine. The process involves rotating the workpiece and indexing it at precise intervals with the dividing head while the milling cutter is fed into the workpiece at an angle.
The spiral milling process is commonly used in the manufacture of gears, screws, and other components that require a helical or spiral shape. The process is often used in conjunction with gear cutting, where the gear blank is mounted on the dividing head and the cutter is fed into the workpiece at an angle to produce the helical teeth.
Spiral milling with a dividing head requires a high degree of precision and accuracy to ensure that the spiral groove is cut with the correct pitch, depth, and angle. It is commonly used in the manufacture of precision components and requires skilled operators and specialized equipment.
It is also considering how secure your workpiece, table, and dividing head are before carrying out this operation. It can be very dangerous if set up wrong. Guards are a must for this.
“Hand of the dividing head”
Dividing heads are known to be “handed” This refers to where the hand wheel is in relation to the holding device. Therefore forcing you to have the dividing head on one side of the bed.
Adjusting the angle
Some times, you will need to tilt the angle of the dividing head, this will allow you to add another axis to your cut. To achieve this, you can loosen the “Blocking bolts” and tilt the head to the required angle. You can then tighten the “Blocking bolts” to secure the dividing head
The internals of a dividing head
Setting up a dividing head
Different methods of taper turning
Select the dividing head and indexing plates appropriate for the workpiece and machining operation.
Ensure that the dividing head and machine bed are clean and that there is room for the dividing head.
Know which “hand” the dividing head is and be ready to place it on the appropriate side.
Ask for help if the lift requires assistance.
Put dividing head and tailstock onto the machine
Loosely tighten bolts onto the tailstock and dividing head to secure them in place
Check the alignment of both the head and tailstock with a DTI in relation to the spindle
Once checked, tighten the bolts fully to secure the work-holding device.
The indexing mechanism of a dividing head consists of a spindle, a worm gear, and an indexing plate. The spindle is connected to the workpiece, and the worm gear is driven by a handle or a motor. The indexing plate has a series of equally spaced holes or notches around its circumference.
When the handle or motor is turned, the worm gear rotates the indexing plate, which in turn rotates the workpiece. The goal is to accurately divide the full rotation of the workpiece into a desired number of divisions.
ISO symbols for calculations
n = rotational speed in rpm
Vc= surface speed in m/min
D = diameter of part
RA = surface finish in microns CLA
f = feed per revolution
rԑ = tool nose radius
Ap = depth of cut in mm
Pc = power used in cutting
T = time in seconds
Q = metal removal rate (cm3/min)
Vf = feed rate in mm/min
The different type of threads that exist
The spindle steady
Form tool method
Lathe Faceplates
This fits the back end of the spindle. Its function is to hold a long workpiece sticking out of the back end of the spindle. This is not because there are any means of machining it here but to hold it straight and/or if it is very thin from thrashing about.
The tool’s cutting edge length must be greater than the taper length. Since the entire cutting edge removes the metal, it will produce a lot of vibration and hence a large force is required. It is done at a slow speed.
Taper turning attachment method
useful formulas for getting started with dividing head maths.
Turns of crank = 40/N
for angular indexing Turns of crank = A/ 9°
The faceplate on a lathe is a crucial component that serves several purposes. Its primary function is to mount and secure the workpiece during machining operations. The faceplate is typically a flat, circular plate that attaches to the spindle of the lathe. It has a threaded center hole that matches the lathe spindle's thread, allowing it to be screwed onto the spindle.
A Taper Turning Attachment may be used for longer tapers if the tapers are longer in length. In these taper turning methods, a different attachment of the lathe machine is used by using a bottom plate or bracket. A taper-turning attachment is attached to the rear end of the bed. It has a guide bar, which is usually pivotal at its center. The guide bar has the ability to swing, and it can be set at any required angle. It has graduation degrees.
Once the faceplate is attached to the lathe, the workpiece can be mounted onto it. The workpiece is usually attached to the faceplate using screws, clamps, or other fastening mechanisms. The faceplate provides a stable and rigid platform for the workpiece, ensuring that it remains securely in place during machining operations.
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A dividing head is a specialized device used for dividing a circle into equal parts. It is primarily used for indexing and cutting gears, splines, and other components with regular spacing. Dividing heads have a spindle that can be rotated by hand or through an indexing mechanism. The spindle is usually equipped with a chuck or collet to hold the workpiece, and it can be tilted to set the workpiece at the desired angle. Dividing heads often have a graduated scale or index plate to facilitate precise positioning of the workpiece.
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A rotary table is a circular table that can be rotated around a vertical axis. It is used for precision positioning and machining of workpieces at various angles. Rotary tables are typically mounted on a milling machine or drill press and can be tilted to set the workpiece at the desired angle. They are usually equipped with a chuck or other means of securing the workpiece. Rotary tables often have graduations or index marks around their perimeter to facilitate precise positioning.
Types of rotary table
Angular:
These are your most common type of rotary table, you’ll notice the dial on the table has lines and markers for 360 degrees of movement
indexable:
These are rarer than angular, however are just a useful, these tables work with “index plates” that allow the user to cut angles in increments.
Drilling: The dividing head is used to drill equally spaced holes in a workpiece. The workpiece is rotated, and the drill is fed into the workpiece to make the holes.
Here is a comparison between a left and right-handed dividing head. you can see that depending on where the rotation hand wheel is, will dictate what side of the bed you will be putting the holding device
This diagram shows the inside of a dividing head and how rotating the index plate will in turn rotate the head. When we “disengage” the head for cutting. We normally remove the connection of the worm shaft and gear to allow no accidental rotation.
You may also notice that by moving the index pin to the wider or smaller arc we will in turn affect the movement between the worm shaft and gear.
Fixed steady
Tailstock set over method
Generally, when the angle of the taper is very small, this taper-turning method will be employed. The workpiece is placed in the live center. By this set-over method, the tailstock will be moved in crosswise, that is, perpendicular to the lathe axis, by turning the set-over method. This process is known as the “tailstock set over method.”
When it comes to the offsetting of the tailstock in the lathe machine, one thing to consider is the length of the taper. When it comes to the taper, length is important. If the length of the taper varies, the offset will vary as well.
The faceplate enables the lathe to perform various operations on the workpiece, such as turning, facing, drilling, and boring. It allows the workpiece to be rotated at a consistent speed and accurately machined to the desired dimensions and shape. Additionally, the faceplate can accommodate larger and irregularly shaped workpieces that may not fit onto a standard lathe chuck.
Different types of steadies.
A number of workpieces are to be made on the end of a long round bar that is too big to fit into the spindle of the lathe. If these are parted off they might be supported by the tailstock for most of the time, when parting off there always comes a point where there is not enough metal left to provide enough rigidity for the tailstock to support the main part of the bar. The solution is to support just to the left of where it will be parted off by using a fixed steady.
Traveling steady
The traveling steady is a steady that is fixed to the saddle and moves along either just in front or just behind the cutting tool. Its function is to stop long thin workpieces from bending under the pressure from the cutter.
