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While the boring process enlarges a pre-drilled hole, reaming is a finishing process that follows the initial bore to finish diameters and surface. High-speed reamers utilize faster speeds and feeds with multi-edge tools tipped with carbide, cermet, or PCD, and thin film coatings improve performance. A step beyond standard reaming, high-speed reaming improves hole quality, achieves closer dimensional tolerance, and delivers exceptional surface finish. High-speed reamers offer multiple configurations, including expandable, solid, and replaceable ring reamers. As parts are reamed, a high-performance reamer will start to wear. Consequently, using a high-quality metalworking fluid is critical to assure part quality and extend tool life. When using metalworking lubricant, be sure it reaches the cutting edges for prolonged tool life. Other high-speed reamer performance considerations include:
Generally, a boring project will focus on pre-drilled holes' sizing, concentricity, and straightness. Operators achieve these three objectives by enlarging the holes while adhering to the specifications of the project using different boring machines. Types of boring machines include vertical, horizontal, and jig to meet standard boring requirements. However, if the project requires demanding machining and materials, more complex boring procedures are needed, such as:
As with much of the manufacturing industry, automation is a significant part of the boring When deciding to use an automated boring machine, the operator needs to consider the application, the precision required, power needed, the cost vs profit, and the time constraints to meet any deadlines. Let’s look at the different types of machines used in boring automation.
Boring heads hold cutters, which are the tools that actually remove material, in position as they rotate to bore holes to the specified diameter. There are several boring head options for boring holes and secondary boring operations that could be applied to that simple operation. Let’s review some of the different ones.
The process of machine boring provides many advantages beyond enlarging a previously drilled hole to the required size and finish. When done with a Computer Numerical Control (CNC) machine, the multiple benefits of boring machining include:
A boring project that meets all the specified requirements of enlarging a pre-drilled hole starts with knowing the fundamentals. While experienced machinists are well-versed in these boring basics, the beginning operator will find this six-step checklist helpful.
When boring on milling machines, it is generally more complicated than operations on turning machines, such as a lathe. A lathe moves the boring tool in increments. On the other hand, the boring tool or boring head needs adjustments to produce the correct hole size when performing the operation on a mill. Lathe boring tools can make holes of any size, provided the bar fits into the holes. However, boring heads are limited to a specific range on milling machines. Because the boring bar on a mill must be adjustable to achieve the correct size using an adjustable boring head, the setup can be more complex for the operator.
When setting up a boring project, the operator has the choice between a carbide or steel boring bar. The question is which one? In this blog we provide information to help make that choice.
Steel Boring Bars
The standard steel boring bar has a common length to diameter ratio of 3 to 1. However, an operator can make adjustments to achieve ratios of 4 to 1 or 5 to 1. A length to diameter ratios of 10 to 1 can be attained when using a steel dampened boring bar. A steel bar can be modified while it is more difficult with a carbide boring bar.
Carbide Boring Bars
A carbide bar offers diameter ratios up to 6 to 1 with 14 to 1 ratio possible with carbide reinforced dampened bars. While a steel boring bar is somewhat flexible, carbide is extremely rigid, allowing for a much higher stickout with less chatter.
Any operator that has bored deep holes knows that chatter (vibration) is an ongoing challenge. To overcome this issue, consider a dampened boring bar. Keep in mind that the material of the bar and the length to diameter ratio determines its effectiveness.
Finish boring completes an existing hole producing a close hole tolerance, correct positioning, and a high-quality surface finish. Generally, it is used with small cutting depths below 0.5 mm (0.020 inch). In contrast, a straight cut in the initial hole when using a rough boring tool does not matter, it will bore true because of its forces are axial. Finish boring tools will likely follow a set path and a longer hole makes it easier for the tool to bend during cutting. Take extra caution to be sure a long hole is true before the finish pass.
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Finish boring work within an existing hole to produce a tight hole tolerance, proper positioning, and a high-quality surface finish. It can be an exacting operation where one inaccurate hole can ruin the part. To avoid this result, the drilled hole needs to be prepped by the rough boring process before finish boring takes place. Rough boring removes and prepares the hole for finishing using pre-machining, casting, or forging. The material stock also is a factor whether rough finishing will be needed. Depending on the stock allowance, the use of a rough boring tool could be recommended to avoid multiple finish passes with the finish boring tool.
With a horizontal boring mill or a vertical boring mill machine available, when would you need a boring mill machine? Let’s consider the reasons.
Large Parts
When you have very large workpieces, a boring mill is exactly the machine you need. With its larger configurable space, a boring mill can mount larger workpieces than a horizontal milling machine.
The boring process takes place after other hole making operations, such as drilling or reaming, make the initial hole. Using the existing pre-drilled hole, boring produces more accurate size holes to meet the specific tolerance specifications. Because of the exacting requirements of the boring process, operators should adhere to the following best practices.
When operating a boring bar excessive machining vibrations or chatter can occur because of several issues. To assure you’re maximizing efficiency and producing the best quality part finish, you must avoid basic mistakes that could be causing tool chatter in the boring process. In this blog we will discuss several tips to reduce and eliminate tool chatter.
Dull Cutters
When using a dull cutting tool, chatter will occur because the cutting force necessary is greater. The more a cutter is in operation, the more it will have galling or built-up edge (BUE). To avoid this problem, inspect your tool before operation to determine it has a a sharp cutting edge and fits your exact application.
Incorrect Speeds & Feeds
Using too high of a chip load in the boring process causes deflection, which increases the chances of tool failure. A chip load that is too low causes the tool to bounce off the material because it doesn’t allow the tool to cut enough. Both errors cause chatter and poor quality. It is critical to use the speeds and feeds recommended for the tool when running a boring bar.
No Workpiece Support
Poor or no support on the workpiece in the boring application will result in chatter. Be certain the correct workholding device is solidly set in place to ensure your setup is as rigid as possible. Secure tool holding is also essential for the proper boring performance.
Poor Starter Hole
Beginning a boring project by drilling a proper starter hole ensures the boring bar has sufficient contact with the workpiece for a stabilized cut. The boring bar could deflect off the workpiece if the starter hole is too large and will not have enough clearance if the hole is too small, leading to tool wear and eventual failure. The two critical dimensions to consider when selecting a drill to prepare the workpiece are the head width and minimum bore diameter.
Universal DeVlieg provides innovative and cost-cutting tool holding and high precision boring solutions to the machine tool industry, servicing a diversified customer base. The combination of over 32,000 active part numbers, over 10,000 standard items, and our technical support staff deliver design engineering expertise that is unmatched in the industry. To learn more about Universal DeVlieg, contact us This email address is being protected from spambots. You need JavaScript enabled to view it. or 877.308.3077 or visit at universaldevlieg.com.