| 摘要 |
A check ring is mounted around a shaft of a screw tip that is mounted on a front part of a screw, whereby a resin is prevented from flowing back from ahead of a conical portion toward the screw. Projections are provided on a front end surface of the check ring. In measurement, a rear end surface of the conical portion of the screw tip and respective end surfaces of the projections are brought into contact with one another, whereby gaps are created between the screw tip and respective root surfaces of teeth of the check ring. By doing this, resin passages can be secured around contact surfaces between the rear end surface of the screw tip and the respective end surfaces of the projections of the check ring.
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