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Because in any real-world process, there is always uncertainty, and if you measure with enough precision you will always find variation in dimensions. Tolerances are specified so the machinist knows what is 'tolerable' and what is not acceptable. Assuming you are working in inches... A drawing dimension might be 1.50 +/- .03 . That would usually be a pretty easy tolerance to hit on a machined part. The machinist knows he doesn't need to be obsessive about this operation, and it will fit into where it is going as long as it is between 1.47 and 1.53 . He can measure it with a scale. Now, if it is 1.5000 +/.0001, it is much more difficult. The machinist needs to be very carefull here. He's going to need a good setup on good machinery, and something very precise to check the part with, in order to make a part that works. It is crucial that engineers and designers think about the tolerances they put on part drawings, because overly tight tolerances cost money, and overly loose tolerances might result in assemblies that don't work. Most of the time, the machinist does not know the context the part will be used in, so he/she shouldn't be left to make those decisions himself. When making parts on NC equipment right off CAD models, it is necessary to provide tolerance guidance to the machine shop to make sure the final part meets the need. Critical dimensions need to be identified at a minimum.
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Can a pneumatic control valve be used with hydraulics?
No. There are a few reasons why a pneumatic control valve can not be used with hydraulics applications. Firstly, pneumatic seals are incompatible to the chemical properties of hydraulic oils and they do not have the strength to accommodate the high pressures produced by a hydraulic system. Secondly, pneumatic valves are not designed for high pressure operation and the component would get damaged, burst or crack. Finally, the tolerances within pneumatic components would allow by-passing due to the slacker tolerances compared to hydraulic components. By-passing causes all sorts of problems by itself: Over-heating, leaking, internal structure damage of the component.
What are tolerances in measurements?
Engineering measurement tolerances are the permissible limits of variation in measurements. Example a piece of steel 25mm square where it would be allowed to be +.001mm or -.001mm on this size. The plus or minus is the tolerance
What is the definition of piping class?
Pipe class is a collection of most compatible components considering dimensional and material properties for the intended service over a range on pressure and temperature specified.
What are the 3 types of tolerances used in mechanical drawings?
limit, unilateral, and bilateral
What would you use to align something in a four jaw chuck on a lathe?
It depends on the surface finish of the workpiece. For machined surface a magnetic base dial indicator is used. For rough or un-machined surfaces a surface gauge is used.
