Boring Machining: Definition, Process, Uses, and Types
During manufacturing, some parts may require holes of different sizes in the workpiece. Such holes are produced using a variety of techniques including boring machining.
Boring machining allows operators to modify holes that already exist in a workpiece. This process is compatible with many types of materials, and it can efficiently process holes achieving tight tolerances.
In this article, you’ll learn all you need to know about boring machining. Its definition, how it works, its advantages, challenges, types of boring machines, and tips for optimal boring.
What Is Boring Machining?
Boring machining is a subtractive manufacturing process that uses a specially designed cutting tool to enlarge an already drilled or cast hole. Therefore, the primary function of boring is not to create new holes but to process existing holes.
This technique is utilized when an application requires greater accuracy and exceptional finish. In fact, when creating wider holes, boring offers higher precision and dimensional accuracy compared to other methods such as drilling.
There are different boring tools, each with distinct applications and benefits. They include lathes, boring mills, and jig borers. While these tools operate in different ways, they all accomplish the same three basic operations;
- Enlarging holes to achieve the right size and finish.
- Creating concentric holes with an external diameter.
- Straightening preexisting holes and correcting casting defects.
How Does Boring Machining Work?
Boring machining is conducted on a lathe, with a boring bar fitted with a suitable cutting tool. Alternatively, this process can be done using milling machines.
Before the machinist can start the boring operation, they’ll need to select a suitable cutting tool depending on the dimensions of the desired hole. Next, the workpiece is securely clamped onto the machine. The chosen cutting tool is then mounted onto the machine’s tool holder and aligned with the pre-existing hole.
With the setup completed, the machine is switched on, and the cutting parameters are chosen. The spindle speed, feed rate, and depth of the cut will depend on the material of the workpiece and hole specifications.
When using a lathe machine, the boring bar is inserted into the existing hole. As the machine spins the workpiece, the stationary cutting insert trims the internal edges of the hole and therefore expands it.
If the operator opts for a milling machine, the boring process is slightly different. In this scenario, the workpiece remains stationary while the boring bar rotates and widens the hole.
Whether you’re working with a lathe or milling machine the basic principle remains the same. The boring tool engages with the workpiece to progressively widen the initial hole until the desired size and surface finish are achieved.
What Are the Types of Boring Machines?
Boring machines are available in a variety of styles and sizes. Each comes with unique features, making it suitable for specific machining applications. Here are the most common types of boring machines.
Horizontal boring machines
As the name suggests, a horizontal boring machine is designed to bore holes that are horizontally aligned. It consists of a spindle with a horizontal orientation, and this allows for versatility in terms of the workpiece size and shape.
Horizontal boring machines are often used for large and robust parts such as engine frames and machine housing. Besides boring, this equipment can also be used for drilling, milling, and reaming.
Vertical Boring Machines
A vertical boring machine is a specialized milling machine designed to handle large workpieces that require precise machining. It has a vertically aligned spindle which holds the cutting tool.
During vertical boring machining, the boring bar approaches the workpiece vertically to perform the desired operation. Vertical boring machines are suitable for heavy workpieces and large holes and they are capable of achieving tight tolerances.
Precision Boring Machines
A Precision boring machine offers exceptionally high standards of accuracy and great surface finishes. Thanks to features such as digital readouts, adjustable spindle speeds, and accurate feed rates, these machines are ideal for applications requiring high precision and tight tolerances.
Machinists often use precision machining in the aerospace, medical, and automotive industries. Besides enlarging holes, this technique is suitable for rectifying defects in existing holes with high dimensional accuracy. Precision boring machines can either be vertical or horizontal type.
Table Type Boring Machines
Table type boring machines are the most common type of horizontal boring machines. They are so named because they consist of an adjustable table that holds the workpiece. Table type boring machines are used for general purpose work that may call for other operations in addition to boring. They are versatile with applications in a variety of industries including automotive, construction, and aerospace.
Floor Boring Machines
Unlike a table-type boring machine, a floor-boring machine does not have a table. Instead, it has floor plates with T-spaces designed to hold the workpiece.
Floor boring machines are built to machine massive parts that are difficult to mount and adjust on a table. They are commonly used in industries such as shipbuilding, construction, and heavy machinery manufacturing.
Applications of Boring Machining
Boring machining is a highly effective process for enlarging existing holes with a high degree of accuracy. One of the most common applications of this process is in the production of engine cylinders and engine blocks in the automotive industry.
In the aerospace field, this technique is used to fabricate precise and accurate holes for engine components.
Sometimes boring machining plays an aesthetic role. For example, it may used to process decorative holes for jewelry and furniture pieces.
What are the Advantages of Boring Machining?
High precision and accuracy
In boring machining, the cutting tool is lined up with the centerline of the existing hole. This results in higher accuracy compared to techniques such as drilling that utilize the overall position of the hole.
Also, CNC boring minimizes the occurrence of errors producing perfect parts consistently.
Speed and efficiency
Boring is a fast manufacturing technique. This contributes to swift production and, therefore, a shorter time to market. The efficiency of this process offers a competitive advantage for businesses as their products are available for sale faster.
Exceptional surface quality
Boring can create holes with a fantastic surface finish. For applications where top-quality surface finish is non-negotiable, machinists often opt for fine boring machining process.
Versatility
You can conduct boring processes on different machines, using either a horizontal or vertical setup. Also, a single boring tool is capable of machining holes of varying diameters.
Compatibility with CNC technology
Boring machining is compatible with CNC technology. CNC boring uses boring machines that are equipped with cutting tools that are directed by computer numerical control technology to perform precise tasks.
CNC machining reduces the need for manual intervention and therefore lowers the risk of human errors. Fabrication shops can also save on labor costs and enjoy a smooth production process.
Suitable for complex tasks
CNC boring is capable of performing complex machining operations. It is used to create elaborate patterns and machine holes of different sizes with a high standard of precision. During mass production of parts, this technology supports the creation of high quality, identical products.
What are the Challenges in Boring Machining?
Boring machining is a popular manufacturing process that has proven effective for applications that require precision holes with excellent surface finish. However, like with any other machining process, there are challenges associated with boring processes. Let’s explore the common issues and how machinists can solve them.
Machine Wear and Tear
During the cutting process, the cutting tool experiences friction resulting in wear and tear over time. Damaged tools result in bigger issues including lower quality parts and decreased productivity.
To address this concern, operators need to use proper cutting parameters, ensure that boring machines are well-lubricated, and perform regular machine maintenance. These procedures improve the lifespan of cutting tools and enhance the quality of machined parts.
Machining Error
Machining mistakes can occur during boring operations affecting the quality of the final parts. Common causes of boring errors include;
- Incorrect cutting parameters
- Improper machine setup
- Choosing cutters that are incompatible with the workpiece material.
Practices such as setup adjustments and using the right cutting parameters and cutting tools can prevent common machining errors.
Finishing and Quality Control
Boring parts may experience surface finish issues such as cutting lines and scales. This is especially common with harder materials which are more prone to rough surface finishing.
The feed rate is crucial to achieving a fine surface finish. Excessive feed rate can result in chatter which causes a poor surface finish. Other possible causes of surface finish issues are poor chip evacuation and wrong insert radius.
Important Tips for Optimal Boring Machining
As with any other machining process, optimizing boring operations ensures high-quality end products. Here are some tips and tricks to help you refine boring machining processes.
Choose the right tools
Different applications require different boring tools. Selecting the appropriate equipment ensures precise and accurate holes. Conversely, if you’re using the wrong boring equipment, you run a higher risk of reduced efficiency, accuracy, and poor performance.
Opt for quality coolants and lubrication
Boring machining produces heat and creates friction which can affect the process. By using high-quality coolants or lubricants, machinists can regulate the temperature of cutting tools, improve surface finish, and prolong the lifespan of the tool.
Optimize cutting parameters
The proper cutting parameters will depend on factors such as the material you’re working with and the job’s particular requirements. Before machining, confirm that you’re using the right speed, feed rate, and depth of cut. This minimizes the risk of errors while improving efficiency.
Maintain boring equipment
Boring machines are subject to tool wear over time. To maintain accuracy and boring quality, operators need to check and replace defective parts, clean the equipment regularly, and lubricate moving parts.
Ensure proper machining setup
For the best results, boring machines need to be correctly set up. This includes ensuring that the workpiece is securely clamped to prevent any deflection during machining. Also, verify and correct spindle positioning and dynamic balance accuracy depending on the application.
Boring Machining Vs. Other Machining Processes
Boring machining is a popular technique used to process existing holes when manufacturing parts. That being said, there are other machining processes that can be used to create holes. Understanding how boring compares to the other techniques helps machinists choose the right process for a specific project.
Boring vs Drilling
Drilling is a manufacturing process that uses a drill bit to create simple holes of different sizes. Boring machining is conducted on drilled holes (or other existing holes) to enlarge them and improve surface finish and accuracy.
Drilling is often used for smaller holes while boring offers more accuracy on wider holes. Another significant difference between these two processes is the level of precision. Drilling has an accuracy level of 0.02 inches while boring machining offers higher accuracy of about 0.0005 inches. Both boring and drilling have pros and cons depending on the specific project.
Boring vs Turning
Like boring and drilling, turning is a subtractive manufacturing process. However, while boring removes material from the inside of a hole, turning removes material from the external section of the workpiece.
Another distinction between these two techniques lies in the cutting tools. Boring utilizes a single-point cutting tool to widen existing holes and turning utilizes a stationary non-rotatory cutting tool. Also, turning typically removes a smaller amount of material.
Both boring and turning operations are conducted on a lathe machine. However boring holes can also be done using other devices that resemble a milling machine.
Boring vs Reaming
Boring and reaming are similar in that they are both used to expand and refine existing holes. However, there are some differences between these processes. First, reaming removes small amounts of material from the inside of a hole to give it a better finish. Conversely, boring can remove more material from the workpiece creating a larger diameter hole.
Boring has a higher accuracy level of 0.0005 inches compared to 0.001 inches for reaming. Also, boring is typically a slower process compared to reaming.
Author
Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.