Metallics DS183M 10 x 1-1/4 in. 5/16 Indented Hex Head Slotted Sharp Point Tapping Screws - Steel Zinc - Each

The Metallics DS183M is a Type A tapping screw with a gimlet (sharp) point, so it forms its own thread in a pilot hole in sheet metal, duct, or light gauge steel. You still drill or punch a clearance pilot hole; the screw cuts the thread as it drives. It runs 12 threads per inch over a 1-1/4 inch length.

Either. The head is an indented hex with a slot, so a 5/16 nut driver or a flat blade both work. Head width across the flats measures 0.305 to 0.312 in., width across corners 0.34 in., and the slot is 0.05 to 0.06 in. wide and 0.057 to 0.072 in. deep. Electricians normally run these with a nut driver and keep the slot for tight spots where the driver will not seat square.

Both are flagged compliant on the DS183M. Country of origin is listed as multiple, so if your contract requires a specific origin on the submittal, that is the item to pin down on the order rather than the compliance flag.

No separate washer needed. The indented hex head carries an integral washer face with an outside diameter of 0.384 to 0.414 in. and a thickness of 0.019 to 0.031 in. That spreads the bearing load on thin sheet and gives a flat seat against a box or strap. Head height is 0.105 to 0.12 in.

They sell by the thousand. Order minimum is 1000 pieces, supplied in a box. Other sizes and quantities can be had by request.

The DS183M is heat treated to Rockwell C28-38 and holds a 48 lb-in minimum torsional strength, made from AISI 1016-1024 steel. That is the standard case hardened range for self-tapping into light structural steel. Keep the driver speed down and do not over-torque once the head seats, since the hardness that lets it cut thread is also what makes it snap if you keep driving.

These are zinc plated steel, which is a dry indoor to lightly damp duty coating. Fine for panel work, duct, boxes, and interior mechanical spaces. For exterior exposure, wet locations, or anywhere in contact with treated lumber or salt air, go to a stainless or hot dip galvanized tapping screw instead, because zinc plating will bleed rust fairly quickly in those conditions.

Head and body dimensions follow ASME B18.6.3-2010 and the threads follow ASME B18.6.4, with steel to AISI 1016-1024. One caveat for anyone cross-checking a table: dimensions for #9 diameter products in this family are independent of ASME B18.6.4.

Electrical, plumbing, and heating and air conditioning work is the stated field application. In practice that means mounting boxes and straps, hanging duct and plenum sheet metal, fastening panel covers, and securing light brackets to sheet steel where a tapped hole is not practical.

A box comes in at 8.47 lbs with carton dimensions given as 7.25 x 4.5 x 4.5 in. That is a one-hand carry, not a pallet item.