Metallics JDS157SS 8 x 1-1/2 in. 1/4 Indented Hex Head Slotted Sharp Point Tapping Screws - 18-8 Stainless - Each

Either one. The JDS157SS has an indented hex head with a slot in it, so a 1/4 inch nut driver or socket works for speed and a flat blade fits when the driver won't reach. Head width runs 0.244 to 0.250 inch across the flats and 0.272 inch across the corners; the slot is 0.045 to 0.054 inch wide and 0.052 to 0.066 inch deep, so use a cabinet-tip blade rather than a fat general-purpose one if you go the screwdriver route.

The JDS157SS is a Type A tapping screw with a gimlet (sharp) point, so it forms its own thread in a pilot hole in sheet metal, and it will start in thin material or wood-type substrates without a tapped hole. It is not a self-drilling screw, though: there is no drill flute at the tip, so on heavier gauge steel you still drill a pilot. Thread count is 15 threads per inch, built to ASME B18.6.4.

Use caution. Metallics flags that fastening stainless steel parts to aluminum or steel can set up a galvanic couple in some environments, which corrodes the lighter metal around the fastener. Outdoors, in wash-down areas, or anywhere with salt or standing moisture, isolate the joint or pick a fastener that matches the base metal. In dry indoor work the 18-8 stainless is generally the more corrosion-resistant choice.

Yes, the indented hex head carries an integral washer face. Washer outside diameter is 0.322 to 0.348 inch and washer thickness 0.019 to 0.031 inch, so you get a bearing surface roughly a third of an inch across without adding a loose washer. Head height itself runs 0.096 to 0.110 inch.

They ship in a jar of 100, and 100 count is the order minimum. Jar weight is 0.77 lbs. Handy if you are stocking a truck or a shop bin rather than buying loose pieces.

Case hardness is Rockwell C28-38, which is what lets a Type A stainless screw form threads in sheet steel instead of stripping its own point. Bear in mind stainless tapping screws are softer than case-hardened carbon steel screws, so back off the driver clutch and avoid impact driving in thicker gauge.

Both the ARRA and Buy American fields on the JDS157SS are flagged compliant. Country of origin is listed as multiple, so if your specification requires documented origin on the specific lot, request it with the order.

At #8 diameter by 1-1/2 in. length, this size is meant for going through a bracket, strap, or box ear and well into wood framing or a thicker substrate. If you are only fastening sheet to sheet, the extra length will protrude behind the work, so step down to a shorter length in the same JDS series. Metallics lists other sizes and quantities in this line by request.

Head dimensions follow ASME B18.6.3-2010 and the thread follows ASME B18.6.4. That matters if you are matching an existing fastener schedule or submitting on a spec job: the head width, head height and washer face are all dimensioned to a published standard rather than a house profile. One exception worth knowing in this Metallics line: #9 diameter sizes are dimensioned independently of ASME B18.6.4.