Metallics JTSS34 12 x 1 in. Pan Head Square Drive Tapping Screws - Steel Zinc - Each

A #3 square (Robertson) bit. The recess is a square drive sized 3R, measuring 0.133 inch across the flats with a gaging depth of 0.080 to 0.095 inch. The square center opening has slightly tapered side walls and a conical bottom, which is what keeps the bit seated under torque. Stock a #3 square bit in the gun before you start the run.

The JTSS34 is a Type A tapping screw with a gimlet point, so it is made to start in thin sheet metal and soft materials with a punched or drilled pilot hole sized for the thread. The gimlet point draws the screw in quickly, but it is not a self-drilling point, so it will not cut its own hole in heavier gauge steel. For thicker stock, pilot drill first.

That is the intended use. These #12 x 1 in. pan head tapping screws are specified for the electrical, plumbing, heating and air conditioning trades, which is exactly the box, strap, duct and panel fastening work those trades do. The pan head gives a broad bearing surface (head width 0.407 to 0.425 in., head height 0.139 to 0.151 in.) so it holds down a strap or bracket without pulling through.

They ship in a jar of 100, and 100 is the order minimum, so a jar is the smallest buy. Each jar weighs 1.04 lbs. Other sizes and quantities are available by request.

Dimensions follow ASME B18.6.3-2013 for the pan head and square recess, and the thread follows ASME B18.6.4 for tapping screws. Material is AISI 1016 to 1024 steel, case hardened to Rockwell C28-38, with a minimum torsional strength of 83 lb-in. Note that dimensions for #9 diameter are independent of ASME B18.6.4.

Torsional strength is rated at 83 lb-in minimum, with the body hardened to Rockwell C28-38. That is the ceiling to work to, so dial an impact or drill clutch back rather than running it wide open into hard stock. The #3 square recess helps here, since it resists cam-out better than a Phillips and keeps the torque in the screw instead of the bit.

The JTSS34 is carbon steel with a zinc finish. Zinc plating is a mild indoor corrosion coating, so it is fine for dry interior work such as panel, box and duct fastening, but it is not a substitute for stainless or hot dip galvanized in wet, exterior or coastal exposure. For those conditions, move to a stainless tapping screw.

No. The JTSS34 tapping screws are not Buy American compliant and are not ARRA compliant, with country of origin listed as multiple. If the project carries a domestic sourcing requirement, these will not satisfy it.

Thread count is 11 threads per inch over a 1 inch length, a coarse tapping pitch that forms its own thread in the mating material. With 1 inch of screw you want the fastener to pass fully through the part being held and engage at least three threads in the base material for a reliable grip, so size the stack accordingly.