More about Precision Machining

Precision machining is what produces a huge number of both large and small objects that we use in daily life. Each intricate piece that makes up an object requires one level or another of a machinist's skills. Likewise, a tool or machine that has been worn down will often require machine tool calibration, welding, or grooving by a precision machinist. From the production of aircraft aluminum alloys to surgical bone drilling devices and custom automotive tools, precision machining reaches into every technology and industry, including oil and gas. In other words, if an object contains parts, it required precision machining.

Quality precision machining requires the ability to follow extremely specific blueprints made by CAD (computer-aided design) or CAM (computer-aided manufacturing) programs like AutoCAD and TurboCAD. The software can help produce the complex, 3-dimensional diagrams or outlines needed in order to manufacture a tool, machine, or object. These blueprints must be adhered to with great detail to ensure that a product retains its integrity. While most precision machining companies work with some form of CAD/CAM programs, they still work often with hand-drawn sketches in the initial phases of a design.

Precision machining is used on a number of materials including steel, bronze, graphite, glass, and plastics to name a few. Depending on the size of the project and the materials to be used, various precision machining tools will be used. Any combination of lathes, milling machines, drill presses, saws and grinders, and even high-speed robotics may be used.The aerospace industry may use high-velocity machining, while a woodwork tool-making industry might use photo-chemical etching and milling processes. The churning out of a run, or a specific quantity of any particular item, can number in the thousands, or be just a few. Precision machining often requires the programming of CNC devices which means they are computer numerically controlled. The CNC device allows for exact dimensions to be followed throughout the run of a product.

Cemented carbides have been widely applied in cutting tools and wear-resistant components due to their ultrahigh hardness and good wear resistance. However, the disadvantages of limited impact toughness and high cost have restricted their further application. Consequently, cemented carbides are usually joining with ductile steels to combine the advantages of both. Among various materials joining technologies, brazing have been an effective method to achieve high quality dissimilar cemented carbide joints. In this paper, the research status of cemented carbide brazing is reviewed. The materials utilized as brazing filler metal in cemented carbide brazing joints are summarized in detail. Researchers have done lots of works utilizing Cu based and Ag based brazing filler metals which are the most commonly used interlayers in brazed joints of cemented carbide and ductile steel. The effects of different filler metal on wettability, microstructure, phase constitution and mechanical properties of brazed cemented carbides joints are analysed. Besides, a series of newly developed brazing filler material such as nickel-based high temperature brazing filler metal, amorphous brazing filler metal and high entropy alloy brazing filler materials are also involved. These newly developed brazing filler metals have shown great potential in fabricating high quality joints. Finally, the current issues of cemented carbide brazing are reviewed and the develop trend is predicted.

Historically, hardened parts were often ground as many cutting tools could not stand up to the rigorous demands of materials with high hardness. Today, many companies are switching from grinding operations to hard turning, as the benefits are numerous.

Hard turning is typically defined as turning of materials harder than 45 Rockwell C (Rc) although, typically hard turning is considered 58 to 68 Rc. As with any machining application the cutting tool must be harder than the material being machined. With this definition, in theory, a carbide insert could machine 60 Rc material, since most carbide is over 85 Rc. However, the reality is carbide inserts would not be able to endure the heat generated in hard turning.

Cubic Boron Nitride (CBN) is the number one choice for hard turning applications. CBN is a man-made very hard material, second in hardness to Polycrystalline Diamond. CBN offers extreme hardness, toughness, chemical and thermal stability.

The sintered CBN blank is cut into desired shapes which are brazed onto cemented carbide blanks in the form of ISO standard geometries; these are final CBN, single or multiple corner inserts.

A common failure mode with CBN in hard turning applications is flaking of the CBN blank. The cause is often the braze. The CBN tip is relatively small so the brazing area is too, then, the braze softens due to heat and causes the CBN to move, causing the flaking. End-users often lose productivity by moving to a softer CBN grade, that runs slower and does not last as long. However, the root cause is often the braze between the CBN and the carbide insert softened and caused the premature flaking. Another common failure mode is the tip comes off while machine. This is an obvious symptom of the braze softening.

This is the reason Tungaloy has introduced its “CBN WavyJoint”. The WavyJoint is a connection surface between the CBN segment and the carbide insert that is an irregular curving surface, alternating in opposite directions, similar to that of waves. This increases the contact surface between the CBN and the carbide insert by 160%. This feature alone decreases the probability of braze softening significantly.