PURPOSE: To provide a product of constant dimensions with extremely high accuracy by detecting the contact of both works by sensing the vibration generat ed by the contact of both works by a vibration sensor, and advancing the works by the specified dimension.

CONSTITUTION: When a pair of works 17, 18 are joined to each other, either work 17 is rotated relative to the other work 18, and the work 18 is advanced until it is brought into contact with the other work, and is advanced by the specified dimension to obtain a joined product of the preset constant dimensions. When the contact is detected by a vibration sensor 24a, the detection of the contact is detected by sensing the vibration generated through contact of the work 18 with the work 17, and the true time of the contact time point is detected. When the contact is detected, the work 18 is advanced by the specified dimension, and the contact part between the works 17, 18 is heat-generated and melted by the mutual friction. Then, the rotation is stopped, the melted part is solidified, and both works are integrated.