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No, you can't.
If the pilot hole is pierced but the screw is not, consider it a "stop hole" and use spiral fluted tap .
In spiral pointed tap threading, chips leave the material only when the tap chamfer is completely penetrated.
If the spiral pointed tap is rotated backwards in the middle of the pilot hole, chips that are separated from the cutting part of the tap will remain connected to the workpiece.
If the tap is reversed in this state, chips that remain connected to the workpiece may bite into the tap, causing the chipping or screw of the tap to fail.
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spiral pointed tap It seems to have rotated in reverse without penetration |
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| During processing | In reverse rotation |
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| spiral pointed tap During processing, chips are discharged in the direction of tap travel. | Chips that are still connected to the workpiece are bitten when rotating in the opposite direction. |