摘要 |
A method of moulding a hub includes providing a cavity in a mould and arranging therein a pair of axially aligned first core pins (41) of circular cross-section, respective end abutment surfaces of which abut against opposite flat side surfaces (38, 39) of a second, generally rectangular core pin (37) which is disposed perpendicular to the first core pins (41) and which has a semi-cylindrical end surface in a plane also perpendicular to said first core pins (41). The surfaces (38, 39) surround the respective end abutment surfaces of the first core pins. When the moulding operation is completed, the first core pins are withdrawn in opposite axial directions and the second core pin is withdrawn in a direction at 90<o> thereto. This produces a hub having a hollow generally cylindrical interior with a central annular groove (24) in the interior hub wall, the groove being interrumpted by an opening (27) formed by the removal of the second core pin from the mould. This method allows a deeper groove to be produced than in the prior art and enables such groove to be of any chosen shape. The method has particular application to the production of a castor body, but can be applied generally to the production of a grooved bore in an article. |