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Hollow bar

Hollow bar – also called the seamless mechanical tubing, – is a tubular product made with properties and characteristics suitable for subsequent transformation into a numerous cylindrical components and hollow products for different engineering purposes. Applications of hollow bar include aerospace, electronics, medical, military, food processing, transportation, chemical and petrochemical industry, nuclear industry. Hollow bars are widely used in general machining industry.

Hollow bars are usually supplied as circular sections, but other shapes are also available. The choice of the most suitable raw material for circular hollow components production, whether the component is a complex precision part or a plain bush, should consider the advantages in using hollow bar as feedstock. When comparing solid bar and hollow bar it is important to remember that the raw material cost depends on the length of material which is used to produce the component. Since the purchase price of basic raw material is based on weight, the factor of price per length is an important factor. Many users prefer hollow bar because of significant savings on machining time and raw material cost. Characteristics of hollow bar have many advantages when compared to solid bar. Hollow bar needs shorter time cycle for the manufacturing of each component and requires no drilling. Drilling from solid bar gives an excessive swarf amount and creates high wastage and frequent machine cleaning compare to less-frequent machine cleaning and low material wastage when using hollow bar. Also coolant isn’t required. So far  hollow bars means more effective technical and cost-efficient solution.

In many cases it is possible to choose a hollow bar with specific outside diameter and wall thickness to make them very close to the dimensions of the final manufactured component. Also the need for some preliminary operations (such as boring and turning) is therefore eliminated or substantially reduced.

Benefits are gained from lower labour cost, reduction in setting-up time, lower tool costs and machine cycle times, lower lubricant usage, overhead costs for each component and machinery maintenance costs. Such problems as swarf handling are also simplified.

General characteristics of the hollow bar are excellent machinability, high resistance to stress corrosion cracking and to general corrosion, pitting and crevice corrosion, high mechanical strength – roughly twice the proof strength of austenitic stainless steels, good hot-working properties, high resistance to erosion corrosion and corrosion fatigue, physical properties that offer design advantages, and good weldability.

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