| 摘要 |
A jig for machining a cylinder block comprising a plurality of through-holes 111 with first protruding portions as a bead 130 with non-contact regions 135 at both sides thereof in the Y direction across the centre of the through-holes. The non-contact regions are formed by providing a section where bead portions are not present or the bead portions are formed with a cut-out and the non-contact regions are not in contact with the cylinder block (200 figure2) at the time of bolting. Second protruding surfaces 140 take the form of shims that are located on the main body of the dummy head and outside the first protruding surfaces. Accordingly it is possible to accurately reproduce the deformation caused by bolting an actual cylinder head to the block with this dummy head. This allows the the cylinder bores (201 figure 2) to be machined under the stress caused by the dummy head and allows the shape of the bores to be much closer to the desired shape when the cylinder head is bolted to the block. |
