There are several problems when such machines are operated in an inert gas medium. The major problem is at the joint between the pin and the bearing. The pin surface gets damaged because of the small rocking angle (less than the angle between adjacent needles), high .contact pressures (above 104 MPa), and comparatively large rocking frequency. Increasing the hardness of the pin surface gives only marginal increase in pin life. The joint is characterized by a fairly high level of vibrations caused by the clearance between the needles and pin. This clearance can be up to 0.06 mm during assembly and can increase with wear.