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Boring is an important procedure for making top quality parts. It gives great surface finishes and accurate dimensions.
That’s why today we will see what boring is and how it works. Also we will know about different boring machines, boring techniques and situations where boring is used.
What is Boring Machining?
Boring machining is a subtractive manufacturing process which accurately enlarges diameter of a hole already present in the workpiece. It’s used to improve the surface finish, roundness and accuracy of a hole that was previously made by other methods like casting or drilling.
How Does Boring Machining Work?
Boring uses one single point cutting tool attached to a boring bar. This tool functions with a speed of more than 100 m/min. Based on the type of machine, workpiece tool movement and rotation changes
In milling, boring tool rotates and the workpiece is fixed. But on lathes, workpiece rotates whereas the boring bar is still. The cutting insert removes material from the inside surface of the existing hole to get better surface finish and accurate diameters.
Types of Boring Machines
Boring machines come in many forms to suit different manufacturing needs. Let’s look at 8 types that serve different industrial applications.
1. Horizontal Boring Machines
Horizontal boring machines use a spindle which is mounted parallel to the ground and it is used for machining big, immovable workpieces. The spindle can move on X, Y and Z axes but workpiece is fixed in its position. This type can do boring at only 0.0005 inches tolerance.
2. Vertical Boring Machines
These machines mostly have a spindle that is hung over a rotating table which holds the workpiece to be machined. The machine does boring with high precision through the synced movement of rotating table and spindle head and it is capable of dealing with workpieces as large as 24“.
3. Jig Boring Machines
Jig boring machines have vertical spindle system combined with digital measuring technology so that they can drill holes at exact spots. In this type of boring machine, the workpiece is fixed and the cutting tool moves in X-Y coordinates. This procedure is also used for drilling and enlarging holes with strict tolerances (0.0001”) and precise alignment in jigs or fixtures.
4. Line Boring Machines
Line boring machines are designed to carry out the operations of enlarging and aligning several holes which are positioned on the same centerline. These machines use a rotating boring bar with single-point cutting tools to remove material slowly and can get the diameter as precise as 0.002%. This procedure also guarantees perfect alignment of mounting holes and bearing journals.
5. Tunnel Boring Machines
Tunnel Boring Machines (TBMs) bore tunnels through soil and rock with a rotating cutter head. The machine uses disc cutters and hydraulic systems for precise boring and conveyors to remove the excavated material. It also lays down the tunnel linings, such as concrete segments, for reinforcements.
6. Cylinder Boring Machines
A cylinder boring machine is mainly designed for reboring the engine cylinder walls in order to remove damaged material. These machines use particular cutting tools and CNC automation software to remove the material and achieve the desired size and smooth finish across several cylinders.
7. Portable Boring Machines
Portable boring machines are field-service tools which are particularly made for on-site repair of heavy equipment. These machines mount directly to the workpiece with three-point carriers and have electric servomotors for controlled material removal. Modular design of these includes control units, drive systems and boring bars.
8. Directional Boring Machines
Horizontal Directional Drilling (HDD) or Directional boring machines are basically used to create underground paths for pipes and cables without surface excavation. The process has three steps which are drilling a pilot hole with a steerable drill head, then enlarging the hole with reamers and, finally, pulling back the utility pipe or cable. The machines, also with the help of a drilling fluid system and an electronic guidance system can make precise underground installations.
Boring Machining Techniques
Boring requires specific techniques. These techniques determine the final quality and dimensional accuracy of the machined parts. The following are well known techniques for boring machining.
Line Boring
Align boring or line boring is a machining procedure which assists in realignment of multiple bores located in common centerline. First, you mount a precision boring bar between support bearings. Then the bar rotates and a single point cutting tool progressively enlarges each bore. Finally, automated feed rates remove material evenly from all holes.
Back Boring
Back boring usually enlarges the holes from the far end towards the entrance side. The process has three steps: insert a specialized tool through the existing hole, deploy the retractable cutting edges at the far end and machine back with controlled feed rates to create counterbores or stepped holes.
Fine Boring
Fine boring is a precision finishing technique that is done on existing holes to get better surface quality and close hole tolerance. It’s a two-step process. First initial cuts remove material by deep cuts at high feed rates of 0.004” per pass. Then a final finishing pass with micro adjustable tools at minimized feed rates produces a mirror like surfaces and exact diameters.
Rough Boring
Rough boring is the initial machining process that removes material quickly from already present holes. The process starts with tool positioning at the hole entrance, then deep cuts at high feed rates of 0.04” per pass. Multiple passes sequentially enlarge the hole and leave 0.02” for final finishing.
Applications of Boring Machining
The boring machining is used in several industries to perform vital functions. The process is especially effective in the applications that need accurate internal diameter dimensions.
Automotive Industry
Boring machining is important in engine block manufacturing for crankshaft bearings, valve guides and cylinder bores. The process reaches cylindricity tolerance of 0.01 mm and surface finish of 0.4 Ra which is vital for engine performance and oil consumption control.
Aerospace Industry
For production of parts like turbine casings, engine shafts, and landing gear struts, boring machining is used due to component safety and outstanding surface finishes.
Heavy Machinery
Through boring machining, foundation components of heavy machinery, for example, shafts, gears, and bearings are produced. These components are integral parts of the machines used in construction and mining industries. Besides that, boring provides the required surface smoothness for minimizing friction and wear in moving parts.
Oil and Gas
The oil and gas industry uses boring machining for safety components like blowout preventers, wellhead equipment, flange fittings, drill pipes and subsea valve bodies. These applications assure leak free operation under high pressure.
Mold and Die
Boring is used in mold and die for producing ejector pin guides, core and cavity alignment bores, cooling channel passages, leader pin bushings, sprue bushings and parting line vents. These features need a 32 micro inch surface finish for better performance.
Benefits of Boring Machining
Boring machining provides many technical advantages in precision manufacturing. Here’s why manufacturers pick this process for important parts.
High Precision and Accuracy
Boring machining gives outstanding dimensional accuracy as it can reach tolerances as narrow as 0005”. Modern CNC boring machines use digital readouts and precise tooling positions to keep hole tolerances within ±0.005 mm for proper fit and better function in applications.
Superior Surface Finish
Boring machining produces great surface finish due to low roughness of 32 µinches Ra than 125 µinches of drilling. The single-point tool, controlled feeds and rigid construction give smooth, durable internal surfaces with less friction and wear.
Better Concentricity and Alignment
The other main advantage of boring machining is that it guarantees that holes are not only of the correct size but also aligned with other features of the part. This concentricity is important for parts like shafts and bearings where misalignment can cause poor performance or failure.
Versatility
Boring machining operations can handle different materials from aluminum to titanium and can make holes from 0.5 to 2000 mm in diameter. Both vertical and horizontal setups give it great flexibility for many machining applications.
Cost Effective
While the initial setup cost of boring machines can be high, the precision and surface finish it can obtain decreases the need for secondary operations like honing or grinding. So it’s cost effective in the long run for high volume production.
Challenges in Boring Machining
Despite its precision abilities, boring machining presents following technical challenges.
- Unstable cutting conditions, wrong tool choice and machine rigidity cause vibration and chatter in boring which results in inaccuracies, poor finish and tool wear.
- Dynamic cutting forces cause boring bars to bend under resistance in deep holes. This deflection should be below 0.001” for better surface quality and precision.
- To obtain surface finish below 0.032” Ra, precise control of tool geometry, cutting parameters and chip evacuation is necessary.
- Wrong measurement tool and not well-calibrated ones can also cause dimensional inaccuracies when measuring bore diameters and geometric tolerances in deep holes.
- Progressive flank wear and crater formation on boring tools can decrease cutting proficiency and dimensional accuracy when machining above 45 HRC.
Tips for Better Boring Machining
Choose Right Boring Tool
Carbide boring bars are good for finishing due to their precision and wear resistance. On the other side, heavy metal bars with more mass and rigidity are suitable for roughing to reduce vibration and deflection.
Cutting Parameters
It is necessary to keep cutting speeds of 200-500 fpm and feed rates of 0.002-0.008 ipr. In case of hard materials, lower feed rates and speeds are more appropriate to avoid tool wear and heat build up whereas softer materials provide greater speeds and feed rates without deteriorating tool life or finish quality.
Machine and Tool Rigidity
Tool setup and machine conditions must be managed carefully. To decrease vibration and deflection, you should keep a ratio of 4:1 L/D for steel bar and for carbide bars, a 7:1 L/D ratio is important. Besides L/D ratio, precision ground toolholders provide maximum contact area to reduce tool movement and misalignment.
Implement Proper Chip Control
Integrate chipbreakers and direct high pressure coolant (synthetic coolant) to the cutting zone. These chipbreakers help in breaking the larger chips into small pieces which thereby keeps them from tangling or wrapping back on the tool. Simultaneously, high pressure coolant cools and removes chips to retain a stable cutting temperature.
Tool Maintenance and Monitoring
Inspect boring tools before each use, clean them after use and check alignment weekly. Check cutting edge visually and measure flank wear periodically. When wear reaches 0.3 mm, replace inserts to avoid tool failure and uphold constant performance.
Richconn’s Boring Machining
Richconn provides boring services through skilled craftsmen and advanced CNC machines. Our facility has horizontal and vertical boring mills that can handle workpieces up to 2300 mm in length. We are skilled manufacturers of complicated components for automotive, aerospace and medical industries with tolerances of ±0.01 mm and surface finishes down to Ra 0.8 µm. Our quality control system also has CMM verification and real time production tracking to guarantee maximum accuracy and reliability.
To Sum Up
In short, boring machining is still important for high precision manufacturing in different industries. With CNC systems, optimized cutting parameters and proper maintenance, modern boring tools or machines can reach outstanding accuracy to 0.0005” and surface finishes of 0.4 Ra.
If you need any type of advanced CNC boring and machining services, you can contact us anytime to talk about your project.
FAQs
Can boring be done on a CNC lathe?
Yes, through their programmed tool paths CNC lathes can do boring. Modern machines, in particular, have automatic tool compensation and digital measurement setups for accurate results.
What determines the boring tool selection?
Some factors such as depth to diameter ratio, hole diameter, surface finish required, material properties and machine rigidity decide the boring tool.
What materials can be machined with boring?
Boring can machine almost all engineering materials, for example aluminum, steel, cast iron, composites and titanium etc.
How is boring different than drilling?
Boring uses a single point tool to refine or expand a hole that is already there. But drilling use a 2 point drill bit and creates new holes. Also boring gives better surface finish and is more precise.
