GRK's R4™ self-countersinking screw has a patented underhead with saw-blade like patented cutting teeth and six self-contained cutting pockets. Together these features act like a circular saw blade, transporting the "drill dust" away from the edge of the screw hole while cutting a perfectly clean hole into even the most brittle materials without cracking any surface treatment. This design enhances the R4™'s versatility by allowing the fastener to countersink into even the hardest woods. The screw head closes the hole off with precision, not leaving any damaged fibers around the head.
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