The classes of components fits


As we know,all spare parts we machined are not a simple components.They should fit with other parts to assemble together.There are several kinds of fits according to the ANSI Standard.They are RC(running or sliding fit),LC(locational clearance fit),LT(transition fit)LN(locational interference fit)and FN(force or shrink fit).


Running and sliding fits define the sliding allowance throughout the range of sizes.The first two classes are used more widely for slide fits because the diameter increase is more slowly in order to maintain the accurate location while there is expense of free relative motion.The RC fits is divided into 9 types as below:

1.       RC1.Close sliding fits are used for high precision parts assembly which should have no observable play.

2.       RC2.Sliding fits are used for accurate location,but is so strict as RC1.It permit some clearance and the fitting parts can move and turn easily.

3.       RC3.The precision fitting parts are used for freely run.It is ofen used for equipment with slow speeds and light journal pressures.But it is not suitable for location where there may be temperature change.

4.       RC4.Close running fits are used for accurate machinery with moderate surface speed and journal pressures.

5.       RC5. And RC6.Medium running fits are used for higher running speeds equipment.

6.       RC7.Free running fits are used for fitting which is not essential or large temperature changes.

7.       RC8 and RC9.Loose running fits are used for material such as cold-rolled shafting and tubing.


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