CNC Rough Machining

Tony

Specialize in CNC machining,Sheet Metal Fabrication, 3D printing(MJF,SLA,SLM,SLS), Casting, Forging, Aluminum Extrusion, Etc

All you need to know about CNC rough machining and CNC finish machining.8 tips to know about CNC roughing and finish machining.

Abstract

Machining or metal cutting is one of the secondary manufacturing processes that involves gradually removing excess material from a preformed workpiece to achieve the desired shape, size, and surface finish. Various operations are performed to meet the basic requirements of machining. Such processes can be broadly categorized into conventional machining, abrasive machining, micro-precision machining, and non-traditional machining. CNC machining is generally divided into roughing, semi-roughing, finish machining, and super-finish machining. Among these, rough machining and finish machining are commonly encountered processes. The following sections will provide a detailed description of the differences between rough machining and finish machining in CNC machining.

Keaword: rough machining; finish machining

Definition:What is roughing and finishing machining?

We know that roughing and finishing are essential processes in CNC machining, but how do we define roughing and finishing? Let’s briefly explain the definition of roughing.

Roughing Machining

Roughing, also known as rough machining or roughing cut, refers to the initial stage of machining where the raw material undergoes simple or primary processing. It is generally performed to prepare the workpiece for semi-finishing and finishing operations, enabling faster and more convenient subsequent machining processes. Roughing is characterized by lower machining accuracy and poorer surface quality. In roughing, the main objective is to quickly remove excess material from the workpiece, without giving much consideration to the surface finish or dimensional accuracy. Larger cutting tools and higher cutting speeds are typically employed to efficiently remove material during this stage.

Roughing is a machining process that occurs at the beginning of part production, where a significant amount of material is quickly removed through high cutting speeds, feed rates, and large cutting depths and forces. The purpose of roughing is to shape the workpiece approximately and remove a large volume of material, leaving sufficient stock for subsequent finishing operations. During roughing, the surface finish may not be smooth, but the dimensional accuracy requirements are relatively low.

In mechanical engineering, roughing generally refers to efficiently removing the majority of excess material and producing a reference product for subsequent machining. It involves removing the irregular surface layer generated during casting or forging processes and performing simple machining operations to achieve a machining allowance of around 5mm. Common machining methods for roughing include rough turning, rough Planing, rough milling, drilling, and rough filing, leaving visible tool marks. Roughing is typically applied to non-interference dimensions or less critical fits, with machining accuracy ranging from IT13 to IT8 and surface roughness (Ra) ranging from 80 to 20.

Finish Machining

Finishing: It is a machining stage that takes place after roughing, primarily aimed at optimizing the surface quality and geometric accuracy of the workpiece. In finishing, smaller cutting depths and forces are used to carefully trim and shape the workpiece. Lower cutting speeds and feed rates are typically employed in finishing to ensure better surface quality and higher precision.

The purpose of finishing is to bring the workpiece to the desired final shape, size, and surface quality, meeting design, and functional requirements. Precision machining techniques are employed in finishing, using high-precision machining equipment. This process involves removing an extremely thin layer of metal from the workpiece surface using tools with high rigidity and finely sharpened edges, utilizing either high or very low cutting speeds or minimal cutting depths and feed rates. Clearly, this process significantly improves the machining accuracy of the part.

Finishing is generally performed after roughing and semi-finishing. Finishing processes include precision cutting operations such as precision turning, precision Planing, precision milling, precision drilling, etc. The machining accuracy in finishing typically ranges from 0.01 to 0.05mm, tolerance grades from IT8 to IT6, and surface roughness (Ra) from 1.6 to 0.8μm.

Why is rough machining often separated from finish machining in CNC machining?

What is the advantage?

To ensure the precision of machining mechanical components, it is recommended to separate rough and finish machining processes. When rough machining is completed, the cutting tools generate high drilling and clamping forces, leading to excessive heat and significant solidification of the workpiece surface. The internal structure becomes uneven and internal stresses accumulate, making it unsuitable for subsequent precision machining. If rough and finish machining are carried out simultaneously, the redistribution of internal stresses during precision machining increases the probability of scrap parts. Here are some advantages of separating rough and finish machining

1. Separating rough and finish machining helps reduce the influence of thermal deformation, allowing for recovery and stress relief. During rough machining, internal stresses can change due to clamping and heating, resulting in deformation. Releasing the stress by separating the processes and allowing the workpiece to cool down helps maintain the dimensional and positional tolerances required by the design.

2. At the beginning of machining, the workpiece is usually in the form of a rough blank. Using the rough blank as a reference during clamping can cause distortion and affect product quality.

3. Separating rough and finish machining is necessary to protect the precision of the equipment. Performing both rough and finish machining on the same equipment for an extended period can lead to a loss of equipment precision, which in turn affects product quality.

4. Proper arrangement of heat treatment processes: After hot machining, residual stresses in the workpiece are significant. By separating rough and finish machining, it becomes possible to schedule stress relief annealing or other heat treatments to eliminate residual stresses before the subsequent finish machining, thus reducing deformation.

5. Increasing efficiency while maintaining accuracy: Rough machining allows for higher cutting depths and feed rates, optimizing material removal. In contrast, finish machining requires smaller cutting depths and slower feed rates to achieve the desired surface quality and precision.

6. In rough machining, due to the large cutting allowance, there is a higher risk of deformation. If finish machining is performed after other surfaces have been machined, it can compromise precision and potentially damage the already machined surfaces.

7. Efficient utilization of machining equipment: Rough and finish machining have different requirements for machining equipment. By dividing the machining stages, the characteristics of both rough and finish machining equipment can be fully utilized, maximizing production efficiency. Rough machining equipment typically has higher power, efficiency, and rigidity, while finish machining equipment offers high precision and low errors, meeting the requirements of the drawings.

8. At the beginning of production, it is common practice to opt for rough machining in order to promptly detect any material defects in the workpiece, thus avoiding potential issues that may arise during subsequent machining. There are many defects in the rough materials, such as pores, bubbles, or unevenness caused by internal impurities or insufficient machining allowance. can be identified after rough machining, facilitating timely repair or decision-making regarding scrapping Time costs can be reduced during production

9. Scheduling rough machining before precision machining and surface finishing helps protect the surfaces that have undergone precision machining and surface finishing processes, minimizing wear and damage.

10. Dividing the machining stages allows for correcting the machining errors resulting from factors such as large machining allowances and cutting forces gradually. By incorporating semi-finishing and precision machining, the machining quality can be ensured.

What types of rough and finishing machining processes there are?

Type of roughing

Rough Turning

Rough turning is a rough machining process in which excess material on the surface of the workpiece is removed through cutting. It is generally used for products with low dimensional and surface roughness requirements. The main goal of rough turning is to remove most of the machining allowance from the surface, and it is advisable to choose a larger cutting depth and feed rate within the allowable range. The cutting speed is correspondingly lower. The achievable machining accuracy of rough turning is around IT12 to IT11, with a surface roughness of Ra 50 to 12.5 μm.

Rough Planing

During rough planing on a machine tool, the processing speed is fast, the workpiece feed rate is high, and the cutting allowance is large. Therefore, the machining accuracy is low and the surface roughness is high. The planer has low machining accuracy, typically around IT13 to IT11, with a surface roughness of approximately 25 μm, and visible tool marks.

Rough Milling

Rough milling is the process of removing a large amount of material using a milling cutter. When a milling machine is used for the rough milling of a workpiece, there is a significant metal machining allowance. Large feed rates and depths of milling are employed, resulting in machining accuracy of around IT13 to IT11 and surface roughness of 50-12.5 μm.

Rough Drilling

Drilling machines can achieve machining accuracy of approximately IT13 to IT11 for hole drilling, with a surface roughness of Ra80 to Ra20. For hole enlargement, the accuracy can reach IT10, with a surface roughness of Ra10 to Ra5. For hole reaming, the accuracy can reach IT7, with a surface roughness of Ra5 to Ra1.25.

Rough Filing

When using a file to process workpieces, there is a large machining allowance and noticeable frictional heat generation. The machining accuracy is very low, generally around IT13 to IT12, with a surface roughness of IT13 to IT12.

Type of finish Machining

Precision Turning

Precision turning is a finishing process in the machining industry that requires meeting dimensional tolerances, positional tolerances, and surface roughness requirements. The goal of precision turning is to achieve all the dimensional and technical requirements of the component. In semi-finishing turning and precision turning, smaller cutting depths and feed rates should be selected, while cutting speeds can be higher. Precision turning requires small cutting depths and feed rates. After precision turning, not only should the geometric dimensions of the workpiece diameter be within specifications, but the surface roughness should also meet higher standards. The machining accuracy of precision turning can reach levels of IT8 to IT7, with a surface roughness of Ra ranging from 1.6 to 0.8.

Precision Planing

Precision planing involves slower processing speeds, lower workpiece feed rates, and smaller cutting allowances during rough planing on a machine tool. Therefore, the machining accuracy is high, and the surface roughness is low. Precision planing achieves high machining accuracy, typically within the range of IT8 to IT7, with a surface roughness of 3.2 to 1.6 μm. The surface has good smoothness and high precision.

Precision Milling

When a milling machine is used for the precision milling of a workpiece, there is a small metal machining allowance, resulting in accuracy within the range of IT8 to IT7.

Precision Drilling

Precision drilling is used for hole drilling with accuracy ranging from IT10 to IT9 (with a drill template), and the surface roughness is Ra25 to Ra6.3. For hole enlargement, the accuracy can reach IT10, with a surface roughness of Ra10 to Ra5. For hole reaming, the accuracy can reach IT7, with a surface roughness of Ra5 to Ra1.25.

What are the advantages of roughing and finishing machining?

Advantages of Rough Machining:

Improved production efficiency: Rough machining focuses on removing excess material and leaving sufficient allowance for precision machining while considering dimensions and tolerances. This allows for the effective utilization of different types of machine tools and enhances cutting efficiency.

Reduced production time: Rapidly reducing the time from “raw material size” to “dimensional requirements as per the drawing.”

Cost savings on tooling: During rough machining, it is possible to use tools that have been retired from precision machining. Since the wear on these tools is typically minor at the cutting edge and can be repaired or refurbished, they can continue to be used for rough machining where surface requirements are not as critical.

Increased machine tool lifespan: Rough machining utilizes high-power, high-rigidity, and low-precision machine tools, while precision machining requires high-precision machine tools. Proper coordination and integration between rough and precision machining contribute to maintaining the accuracy of machine tools over the long term.

Reducing procurement cost of high-precision lathes: Rough machining can be accomplished with general low-precision machine tools, eliminating the need to purchase expensive high-precision machine tools and resulting in cost savings.

Favorable production line layout: Rough machining helps in optimizing the layout of the production line, considering the specific requirements and processes involved.

Advantages of Finish Machining:

Achieving desired specifications: Finish machining is the final stage of the machining process that focuses on achieving the desired dimensions, tolerances, and surface finish of the part. It ensures that the part meets the exact specifications outlined in the design and engineering requirements.

Enhanced surface quality: Finish machining processes, such as fine milling, grinding, or polishing, result in a smooth and refined surface finish. This is important for components that require a high level of aesthetic appeal, improved functionality, or reduced friction.Finish machining can improve machining accuracy and surface quality. The allowance in finish machining is minimal, resulting in reduced machining stress and deformation, which significantly enhances the quality of the parts.

Tighter tolerances and precision: Finish machining allows for the attainment of tight tolerances and high precision. It ensures that the final dimensions of the part are within the specified limits, enabling proper fit, assembly, and functionality.

Improved part performance: Finish machining can enhance the performance of the part by refining critical features, eliminating burrs, and ensuring proper alignment. This leads to improved functionality, reduced wear and tear, and increased durability of the component.

Compatibility with advanced materials: Finish machining techniques are capable of working with advanced materials, including exotic alloys, ceramics, and composite materials. This enables the production of high-performance parts used in industries such as aerospace, defense, and automotive.

Reduced risk of part failure: Finish machining helps eliminate any defects, surface irregularities, or inconsistencies that may compromise the structural integrity or functionality of the part. It reduces the risk of part failure and ensures reliable operation under demanding conditions.

Optimization of surface properties: Finish machining can modify surface properties, such as hardness, roughness, and friction coefficients, to meet specific requirements. It allows for the application of coatings, treatments, or surface modifications that enhance the part’s performance in terms of wear resistance, corrosion resistance, or lubrication.

Quality control and inspection: Finish machining provides an opportunity for thorough quality control and inspection of the final part. This ensures that the part meets the required standards and specifications before it is assembled or delivered to the customer.

High precision: Finish machining focuses on achieving tight dimensional tolerances and precise geometric shapes. It ensures that the final product meets the required specifications and functionality. This high level of accuracy is crucial for industries such as aerospace, medical devices, and automotive manufacturing.

Enhanced repeatability and consistency: Precise machining methods ensure consistent and repeatable results. This is particularly beneficial for mass production, where maintaining consistent quality and specifications across multiple parts is essential.

Reduced post-processing requirements: Finish machining often produces parts with good dimensional accuracy and surface smoothness, minimizing the need for additional finishing operations. This helps streamline the manufacturing process, reduce overall production time, and cost.

Improved efficiency and productivity: With advanced CNC technology and automated processes, finish machining offers higher efficiency and productivity. It allows for faster production cycles, reduced setup time, and the ability to handle complex geometries with high precision.

Design flexibility: Precision machining techniques can accommodate complex and intricate designs, including features such as undercuts, fine details, and intricate patterns. This provides greater freedom for designers and engineers to create innovative and customized products.

Requirements for Rough Machining:

Rough machining does not require high surface quality. It is generally done as a preparatory step for semi-finish machining and finish machining. Since rough machining involves large machining allowances, high machining speeds, and generates significant heat, it places higher demands on machining tools. Typically, high-hardness alloy materials are chosen as tool materials.

Furthermore, during rough machining, the heat generated by the cutting tools can have a significant impact on their lifespan. Therefore, we must employ artificial methods such as using oil, cutting fluids, or air cooling to extend the tool’s longevity.

What should be paying attention to in rough machining?

To ensure the high efficiency of rough machining, we need to pay attention to the following points under normal circumstances. Here are some key considerations:

Advantages of Rough Machining:

Removing Excess Material: In order to improve processing efficiency, coarse processing methods are often chosen to remove a significant amount of excess material, providing a quick machining shape for subsequent precise processing. Pay attention to selecting appropriate cutting tools, such as high-speed steel or carbide tools, which can withstand the high cutting forces and efficiently remove material.

Cutting parameters: Optimize the cutting parameters, including cutting speed, feed rate, and depth of cut, to achieve a balance between material removal rate and tool life. Higher cutting speeds and feed rates can increase productivity, but they should be within the limits of machine capabilities and tool integrity.

Cooling and lubrication: Implement effective cooling and lubrication methods during rough machining to dissipate heat generated during the process. This helps in prolonging tool life and preventing thermal damage to the workpiece.

Machine rigidity: Ensure that the machining setup, including the workpiece clamping and tool holding, provides sufficient rigidity and stability to withstand the forces generated during rough machining. Rigidity is crucial for maintaining accuracy and preventing vibration or chatter.

Safety measures: Follow proper safety protocols when operating machinery for rough machining. This includes wearing appropriate personal protective equipment (PPE), ensuring machine guards are in place, and adhering to safe operating procedures.

Quality control: Although rough machining is focused on material removal rather than achieving high precision, periodic inspections and measurements should still be conducted to monitor the process and ensure that dimensional tolerances are within acceptable limits.

Consideration for subsequent operations: Keep in mind the requirements for subsequent machining operations, such as finish machining. Leave adequate allowances and avoid damaging critical surfaces or features that will be machined in later stages.

Sufficient and reasonable allowance should be considered during rough machining for subsequent finish machining.

Correct referencing, along with the selection of appropriate machining sequence, tool materials, and cutting parameters, should be done during finish machining to ensure the final product quality

The surface quality of CNC machined parts has an impact on their usability, as parts with surface defects can affect their performance. For example, if there are tiny cracks on the surface of a part, these cracks are likely to expand during use, eventually leading to part failure. By paying attention to these factors, rough machining can be performed effectively, maximizing productivity and ensuring the quality of the final machined components.

How to choose the surface finishing tools(cutter) in roughing and finishing machining

During the rough machining stage, we typically choose suitable cutting tools based on the requirements of the workpiece. In the rough machining stage, the main focus is on removing excess material. Therefore, it is advisable to choose a tool with good toughness, low hardness, good rigidity, and lower accuracy. In the semi-finish and finish machining stages, the primary objective is to ensure the machining accuracy and product quality of the part. Therefore, it is recommended to use tools with low toughness, high hardness, high durability, and higher accuracy. The accuracy of the tool used in rough machining is the lowest, while the accuracy of the tool used in finish machining is the highest. If the same tool is used for both rough and finish machining, it is suggested to use the tool that has been retired from finish machining for rough machining. This is because the retired finish machining tools mostly have slight wear on the cutting edge and the coating, which may affect the machining quality in finish machining but have a minimal impact on rough machining.

In rough machining, the cutting process is usually performed in a climb milling mode, while in finish machining, conventional milling is often used to prevent “chatter.”

There are several differences between rough turning tools and finish turning tools on CNC lathes: (1) Rake angle: The rough turning tool has a smaller rake angle, while the finish turning tool has a larger rake angle. (2) Relief angle: The rough turning tool has a smaller relief angle (6-8 degrees), while the finish turning tool has a larger relief angle (10-12 degrees). (3) Tool inclination angle: In rough turning, it is generally set at 5 degrees, and it can be increased to 10 degrees or more in the case of significant vibration. In finish turning, it is typically set at -4 degrees. (4) Principal cutting edge inclination angle: It depends on the stiffness of the machine-tool-workpiece system. (5) Secondary cutting edge inclination angle: It depends on the surface roughness requirements, with a smaller inclination angle preferred for higher requirements. (6) Tool tip radius: For carbide turning tools, the radius is generally set between 0.5-2mm, with a smaller value preferred in rough turning. Rough turning tools and finish turning tools are relative terms. For the same workpiece, the finish turning tool must meet the final machining requirements of the machined surface (usually sharper, narrower chip-breaking grooves), while the rough turning tool can withstand higher cutting forces, has wider chip-breaking grooves, and requires better heat resistance.

The rough turning tool for external cylindrical turning should be able to accommodate the characteristics of deep cutting and high feed rate during rough turning. The main requirements for the tool are sufficient strength to allow for removing a larger amount of excess material in one feed. The general principles for selecting rough turning tools are as follows:

To enhance the strength of the tool head, the rake angle and relief angle should be smaller.

To increase the tool tip strength, there should be a transitional cutting edge. The principal cutting edge inclination angle should not be too small, and there should be chip breakers on the front cutting face.

When finish turning the external cylindrical surface, it is necessary to achieve the dimensional accuracy and smooth surface roughness of the workpiece. Since a small amount of metal is removed during finish turning, it is important to use a sharp tool with a straight and smooth cutting edge. The tool tip can be ground to create a polished section. During cutting, the cutting edge should be oriented towards the surface of the workpiece being machined.

What is the difference between roughing and finish machining?

Differences between rough machining and finish machining in CNC machining:

Different objectives: Rough machining is aimed at quickly giving the part its basic shape based on the required features, and surface roughness is not a critical factor at this stage. On the contrary, the primary goal of rough machining is to remove unwanted material to the maximum extent possible. The difference between precision machining and rough machining lies in the ability to achieve an exceptionally smooth surface finish, high precision machining accuracy, and stringent tolerance requirements. Therefore, in the process of precision machining, the cutting speed needs to be extremely slow.

Surface smoothness and dimensional accuracy: Due to the feed rate, each traditional machining process leaves scallop marks or feed marks on the finish machining surface. These sawtooth-shaped scallop marks contribute to the main surface roughness. Apart from tool geometry, surface roughness also directly depends on the feed rate. Higher feed rates result in poorer surface smoothness. Higher cutting depths also tend to reduce surface smoothness and machining accuracy. In rough machining, higher feed rates and cutting depths are used, leading to inferior surface smoothness. It also cannot provide high dimensional accuracy and tight tolerances. On the other hand, finish machining, with very low feed rates and cutting depths, can improve finish, accuracy, and tolerances.

Different tool usage: Rough machining tools typically feature wavy cutting edges or large chip-breaking grooves, providing a larger contact surface and a significant volume of cutting material. Finish machining tools, on the other hand, usually have sharp cutting edges and high tool strength. The sharp cutting edges and higher strength reduce tool deflection and improve surface quality in finish machining.

Older tools may not be as sharp (i.e., larger nose radius and edge radius) since they have worn during the machining process. The sharpness of the edges and nose limits the achievable surface smoothness during the process. Sharp edges may not withstand high chip loads, but they are necessary to achieve better smoothness and accuracy.

Therefore, old tools can be used in rough machining without significant issues since surface quality is not critical. However, sharp tools should be used in finish machining to achieve better surface smoothness, accuracy, and tolerances. In finish machining, the feed and depth of cut are kept low, so there are no detectable issues with tool breakage or edge chipping due to chip loads.

What types of surface roughness and dimensional accuracy after roughing and finishing machining?

The two most apparent differences between the two machining processes are their different machining objectives. Rough machining is primarily focused on giving the part its basic shape, while finish machining is aimed at improving the desired surface smoothness and dimensional accuracy of the part. Below are approximate values for dimensional accuracy and surface roughness for both rough machining and finish machining processes.

Rough Machining:

Dimensional Accuracy: Typically, rough machining achieves lower dimensional accuracy compared to finish machining. It focuses more on material removal and basic shaping, rather than precise dimensional control.

Surface Roughness: Rough machining results in a higher surface roughness compared to finish machining. The priority is to quickly remove excess material, which may leave visible tool marks or scallop-like surface textures.

Finish Machining:

Dimensional Accuracy: Finish machining achieves higher dimensional accuracy compared to rough machining. It aims to meet specific tolerances and dimensional requirements for the part.

Surface Roughness: Finish machining results in a significantly smoother surface compared to rough machining. The focus is on improving the surface quality, minimizing tool marks, and achieving the desired surface finish.

It’s important to note that the actual values of dimensional accuracy and surface roughness can vary depending on the specific part, machining parameters, and the desired level of precision.

Processing Method		Dimensional Accuracy(IT)	Surface Roughness（Ra）
Cylindrical turning	Rough Turning	IT13～IT11	50～12.5
	Semi-finish Turning	IT10～IT9	6.3～3.2
	FT(finish turning)	FT(finish turning)	IT8～IT6
Face cutting	Rough Turning	IT13～IT11	50～12.5
	Semi-finish Turning	IT10～IT9	6.3～3.2
	FT(finish turning)	IT8～IT6	1.6～0.4
Diamond turning	FT(finish turning)	IT6～IT5	0.4～0.2
Outer-surface milling	Rough Milling	IT13～IT11	50～12.5
	Semi-Precision Milling	IT10～IT9	6.3～3.2
	Precision Milling	IT8～IT7	1.6～0.8
Face milling	Rough milling	IT13～IT11	50～12.5
	Semi-Precision Milling	IT10～IT9	6.3～3.2
	Precision Milling	IT8～IT7	1.6～0.8
High-speed milling	Rough milling	IT9～IT8	3.2～1.6
High-speed milling	Finish-milling	IT7～IT6	0.8～0.4
Planing	Rough planing	IT13～IT11 50～12.5	5.0～12.5
	Semi-precision planing	IT10～IT9	6.3～3.2
	Precision planing	IT8～IT7	1.6～0.8
Surface Grinding	Rough grinding	IT10～IT8	12.5～6.3
	Semi-precision grinding	IT9～IT8	3.2～1.6
	Precision grinding (with dressing wheel)	IT6～IT5	0.8～0.4
External Cylindrical Grinding Internal Cylindrical Grinding	Rough polishing	IT13～IT11	50～12.5
	Semi-precision polishing	IT10～IT9	6.3～3.2
	Precision polishing (with grinding wheel)	IT8～IT7	1.6～0.8
Drilling	Rough drilling	IT13～IT11(￠5 or less)	50～12.5
Drilling	Precision drilling	IT10～IT9(There is a drill mold)	25～6.3
Boring	Rough reaming	IT13～IT11	50～12.5
Boring	Precision reaming	IT10～IT9	6.3～3.2
Reaming	Rough chamfering	IT9～IT8	3.2～1.6
Reaming	Precision chamfering	IT7～IT6	0.8～0.4
Boring (Machining)	Rough boring	IT12～IT11	25～12.5
	Semi-precision boring	IT10～IT9	6.3～3.2
	Precision boring (floating boring)	IT8～IT7	1.6～0.8
Diamond Boring	Precision boring	IT7～IT5	0.8～0.2
Slotting	Rough broaching	IT11～IT13	12.5～25
Slotting	Precision broaching	IT10～IT8	6.3～1.6
Broaching	Rough turning	IT8～IT7	1.6～0.8
Broaching	Precision turning	IT7～IT6	0.8～0.4
Scraping	25mmX25mm	8～25 Points	0.8～0.1
Filing	Hand filing	IT13～IT7	50～0.8
Gas Cutting		IT13～IT11	50～12.5
Welding
Gear Hobbing		IT8～IT7	1.6～0.8
Tapping		IT10～IT8	6.3～1.6
Threading	Using a die	IT9～IT8	3.2～1.6
Ultrasonic machining		0.03～0.005	0.4～0.2
Laser machining		0.01～0.001	6.3～0.4
Electron beam machining		0.01～0.001	6.3～0.4
Ion beam machining		0～0.01	0.05～0.01
Electrochemical machining		0.1～0.01	0.8～0.2
Electrical discharge wire cutting (Wire EDM)		0.02～0.002	3.2～0.4
Electrical discharge or die-sinking machining		0.03～0.003	6.3～0.05
Polishing	Precision machining	IT6～IT5	0.4～0.2
Chemical Grinding	Chemical precision grinding	IT7～IT6	0.8～0.4
Electrolytic Grinding	Electro-precision grinding	0.02～0.001	0.8～0.05
Honing	Rough honing	IT7～IT6	0.8～0.4
Honing	Precision honing	IT6～IT5	0.4～0.2
Grinding	Rough Grinding	IT6～IT5	0.4～0.2
Grinding	Precision Grinding	IT5	0.2～0.1

Conclusion.

In summary, rough machining and finish machining can be distinguished from various perspectives. In general, rough machining involves higher feed rates, cutting depths, and material removal rates (MRR), aiming to remove a significant amount of excess material. As a result, the surface after rough machining tends to have higher roughness, lower surface smoothness, lower accuracy, and larger tolerances. However, it achieves higher productivity due to the rapid material removal.

On the other hand, finish machining is performed after rough machining to refine the part’s shape and achieve the desired surface quality. It typically involves lower feed rates, cutting depths, and MRR, with a focus on removing a thin layer of material from the surface. As a result, the surface after finish machining is smoother, brighter, exhibits higher surface smoothness and has higher accuracy with smaller tolerances.

To produce parts that meet the dimensional requirements specified in the drawings, it is important to consider the specific needs of each part and arrange the machining processes accordingly.

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