Metallics JTSS33 12 x 3/4 in. Pan Head Square Drive Tapping Screws - Steel Zinc - Each

Use a #3 square (Robertson) bit. The JTSS33 recess is specified as driver size 3R, with a recess measuring 0.133 in. across flats and a gaging depth of 0.080 to 0.095 in. The square recess has slightly tapered side walls and a conical bottom, so a correctly sized #3 bit seats deep and resists cam-out when you are driving one-handed off a ladder.

The JTSS33 is a Type A tapping screw with a gimlet point, which is the sharp, pointed thread form made for thin sheet metal and similar light materials. It still wants a correctly sized pilot hole in most metal work; the gimlet point starts and centers the screw rather than drilling its own hole through heavier stock. For drilling its own hole in thicker steel you want a self-drilling (Tek-style) point instead.

No. The JTSS33 is not Buy American compliant and is not ARRA compliant, and country of origin is listed as multiple. If your job carries a domestic sourcing requirement, these will not satisfy it and you need a domestically produced fastener instead.

They ship 100 to a jar, and the jar is the order minimum, so the smallest quantity you can buy is 100 pieces. The filled jar weighs 0.88 lbs.

The JTSS33 is rated to 83 lb-in minimum torsional strength, with the steel heat treated to Rockwell C28-38. That is the figure to watch if you are running them with an impact driver: set the clutch rather than driving to stall, because a #12 screw in thin gauge metal will strip the material well before it reaches that torque.

Pan head, and it sits on top of the surface rather than countersinking. The head measures 0.407 to 0.425 in. across and 0.139 to 0.151 in. high, so it gives a broad bearing surface for strapping, box mounting, and panel work where you are not trying to hide the fastener. If you need the head flush with the material face, a pan head is the wrong profile and you want a flat head screw.

Head and recess dimensions follow ASME B18.6.3-2013, the threads follow ASME B18.6.4, and the steel is AISI 1016 to 1024. One caveat for spec work: dimensions for #9 diameter in this series are independent of ASME B18.6.4.

These are carbon steel with a zinc plated finish, which is a dry indoor and protected-location coating. Zinc plating handles incidental moisture but it is not a marine or sustained-wet finish, so for exterior, coastal, or washdown work step up to stainless or a hot dip galvanized fastener. Typical use is electrical, plumbing, heating and air conditioning work inside the building.

Thread count is 11 threads per inch on the #12 diameter. Size the pilot to the root diameter of the thread for your gauge of material; in thin sheet you can run near the minor diameter and let the gimlet point pull itself in, in heavier stock open the pilot up so you do not exceed the 83 lb-in torsional rating of the screw.

The JTSS33 as catalogued is the #12 x 3/4 in. pan head square drive in a 100 piece jar. Other sizes and quantities in the JTSS series are available by request, so if you need a longer screw for thicker strapping or a bulk box instead of a jar, ask for the matching JTSS part.