Though apparently seems simple but is one of the difficult machining operation, increase in cost due to various operations involved in a preparing key ways- i.e. setting & down time + machining time. Lateral shifting of key ways in process, also it is extremely difficult to set the center line of the keyway exactly symmetrical and parallel with respect to the radial plane. Heavy torsional stresses are concentrated at the corner of the keyway so shaft is weakened. Deviation in width, paralliasm to the axis, inaccuracy in key, is also affect.

The cumulative effect of all the above operational errors calls for an alternative system. Power Transmission by keyless arrangement.