Metallics CSF20F Anchors 1/4 X 1-3/4 Fh Ph Blu Conc Scr St-zn (Jar 100)

The CSF20F is a 1/4 x 1-3/4 inch concrete screw, and a 1/4 inch diameter concrete screw is installed in a 3/16 inch hole drilled with a carbide bit. Drill deeper than the screw will sit so dust has somewhere to go, blow the hole out, then drive the screw with a Phillips bit. No separate anchor, shield, or plug is needed.

Flat head is the countersinking style, so it pulls down into a countersunk or chamfered hole and finishes flush. That is what you want under a cover plate, a flush-mounted channel, or anywhere a projecting head would interfere. If you are fastening a strap or clamp with a flat punched hole, a hex washer head concrete screw seats better against the flat.

The CSF20F is a steel screw with zinc plating and a blue coating. Zinc plating handles interior and intermittently damp conditions. For permanently wet exposure, submerged locations, or treated lumber in contact with the fastener, specify a stainless concrete screw instead of zinc plated steel.

Concrete screws of this type are driven into concrete, hollow and solid block, and brick, as long as you hit solid material and not a mortar joint or the thin face shell of a hollow block. Drill into the solid web of the block where you can. In poured concrete, avoid driving within a few inches of an edge so the hole does not blow out.

They ship 100 to a jar, which is the practical count for a crew mounting strut, straps, boxes, and conduit clamps on a masonry job. The jar packaging keeps them from spilling in a gang box, and the part number for reordering is CSF20F.

A 1/4 x 1-3/4 inch concrete screw drives with a Phillips bit in a standard drill/driver, though an impact driver makes the work faster on a long run. The critical part is the hole: a clean 3/16 inch carbide-drilled hole, blown clear of dust, is what lets the threads cut properly. Driving into a dusty or undersized hole is what snaps heads.