| 摘要 |
<p>A cylindrical screening member (15) for use in screening apparatus for paper making stock is provided with screening perforations (18) of extremely small minimum diameter by first forming the perforations with whatever larger minimum diameter is practical for production by drilling the base material for the screening member, and then subjecting the perforated base shell to a coating operation in which it is covered with a smooth coating (44), of predetermined uniform thickness entirely covering its inner and outer surfaces and also forming a lining for the wall of each perforation which reduces its minimum dimension by an amount equal to twice the thickness of the coating.</p> |
