| 摘要 |
A cementitious tile 60 is perforated using a punch 10 of elongate section having a leading face 16 with a saw tooth profile along its length. The punch may also be used to produce indentations which look like perforations when in situ. Circular punches also having a saw tooth profile may be used. The tooth depth is preferable less than 2mm and the included angle of the tooth profile between 90‹ and 150‹. The punches are arranged on a punch plate (20 Fig 4).
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