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General-Purpose Metal-Cutting Machine Tools
Published in Helmi Youssef, Hassan El-Hofy, Traditional Machining Technology, 2020
Drilling jigs are special devices designed to hold a particular WP and guide the cutting tool. Jigs enable work to be done without previously laying out the WP. Drilling using jigs is, therefore, accurate and quicker than standard methods. However, larger quantities of WPs must be required to justify the additional cost of the equipment. Jigs are provided with jig bushings to ensure that the hole is machined in the correct location. Jig bushings are classified as press-fit bushings for jigs used in small-lot production for machining holes using a single tool. Slip renewable bushings are used for mass production. Bushings are made of hardened steels to ensure the required hardness to resist the wear. The drilling jigs are generally produced on jig boring-machines.
Couplings
Published in J. T. McGuire, Pumps for Chemical Processing, 2020
For the types of pumps used in chemical processing, couplings are mounted one of two ways: keyed cylindrical fit or keyed tapered fit. The former is less expensive and is therefore more common. Cylindrical fits (Fig. 12.17a) are better if sized for interference. Slide fits seem attractive for ease of mounting and dismounting, but are prone to fretting, fatigue, and require a secondary device for axial location. With the appropriate tools, interference fits do not pose a major mounting and dismounting problem. In pumps designed for bearing and seal maintenance without opening the casing, a taper-mounted coupling (Fig. 12.17b) offers easy mounting and dismounting without the limitations of cylindrical slide fits. Taper mounting couplings increase the first cost of the pump. For low speed couplings the use of a taper lock bushing (Fig. 12.17c) offers an easily assembled interference fit mounting. The disadvantages are an increase in coupling size to accommodate the taper bushing and greater difficulty maintaining concentricity. The latter problem affects balance, hence limits speed.
RCAM Case Reliability and Maintenance Component Modeling
Published in Lina Bertling Tjernberg, Infrastructure Asset Management with Power System Applications, 2018
There are many sorts of bushings, and they are classified either according to isolation material on ends, or inside the bushings or to the construction. The bushings on an oil filled transformer are air-to-oil bushings, which means that the isolation material on the ends are air and on the other its oil. The isolation material inside the bushing can be oil, oil-impregnated paper, resin-impregnated paper or gas. Oil-insulated bushings can either have an own closed oil system or share oil with the transformer. The dielectric strength of the isolation material decides the length of the bushing. There are two main constructions of bushings: solid and capacitance-graded bushings. The solid bushing has a central conductor and porcelain or epoxy insulators at either end. They are used in small distribution transformers as well as in large generator step-up transformers. Capacitance-graded bushings are used for all voltage ratings above 25 kV. At predetermined radial intervals, between the conductor and the insulator, conducting layers of oil-impregnated paper or other insulation material are located [232].
Multi-objective optimization of the internal diamond burnishing process
Published in Materials and Manufacturing Processes, 2022
Galya V. Duncheva, Jordan T. Maximov, Angel P. Anchev, Vladimir P. Dunchev, Yaroslav B. Argirov
Typical materials for bearing bushings are the aluminum bronzes, which combine adequate strength and high wear and corrosion resistance. A widely used bronze is CuAl8Fe3, which, because of a lower Al content (below 8.5%), is not subjected to heat treatment but is highly ductile. Therefore, DB can be used to improve the surface integrity (SI) of this bronze.