Metallics JTSF39SS 14 x 1-1/2 in. Flat Head Phillips Tapping Screws - 18-8 Stainless - Each

A #3 Phillips bit. The recess on the JTSF39SS measures 0.276 inch diameter, 0.16 inch deep, with a 0.036 inch recess width, so a #2 bit will cam out and chew the recess under load. Stock #3 bits before you run a jar of these.

Yes, if the countersink is cut for a standard 82 degree flat head. The JTSF39SS head runs 0.427 to 0.462 inch across with a head height of 0.126 to 0.148 inch, and it is dimensioned to ASME B18.6.4-1998, so it drops into any countersink prepped to that standard and finishes flush with the surface.

It needs a pilot hole. The JTSF39SS is a Type A tapping screw with a gimlet point, which is a sharp pointed thread-forming screw, not a self-drilling screw with a cutting tip. It will start in wood or thin sheet on its own, but in steel or aluminum you pre-drill and let the screw form the thread. If you want a screw that drills its own hole in metal, you want a self-drilling (Type TEKS style) screw instead.

Mechanically yes, but watch the corrosion. Metallics flags that fastening 18-8 stainless parts to aluminum or steel can set up a galvanic couple in some environments, which attacks the softer base metal around the screw. Outdoors or in wet or coastal conditions, isolate the joint or choose a fastener matched to the base material. Indoors and dry, it is a normal practice.

10 threads per inch on a #14 diameter shank, with a 0.41 inch gaging diameter, threaded to ASME B18.6.4. That is the coarse Type A pitch, which is what gives it bite in sheet metal and wood rather than the finer pitch of a machine screw. If your existing holes were tapped for a machine screw, these are not the replacement.

The JTSF39SS is rated to a 125 lb-in minimum torsional strength. Drive it with a #3 Phillips bit and back your impact driver or clutch off below that figure, especially in steel, because stainless work-hardens and a Type A screw twisted past its limit will shear at the shank rather than strip the hole.

Metallics lists the JTSF39SS as both ARRA compliant and Buy American compliant, with country of origin recorded as multiple. For a government, school, or transit project with domestic-content language in the spec, that compliance flag is the one your submittal package needs, and the dimensional standard on record is ASME B18.6.4-1998.

18-8 (the 300 series austenitic grade) handles exterior and damp interior service far better than plated carbon steel, which is why these get used on enclosures, strut, and sign work. It is not the grade for direct salt spray or pool chemical exposure; 316 is the choice there. Also remember the galvanic note Metallics gives: stainless against aluminum or steel can corrode the base metal in wet environments.

They ship in a jar, 100 count minimum. Jar weight is listed at 1.52 lbs. Metallics notes other sizes and quantities are available by request if 1-1/2 inch length or #14 diameter is not what your job calls for.

Protrusion gaging on the JTSF39SS is 0.029 to 0.049 inch above, measured per the ASME B18.6.4-1998 dimensions. That tells you the recess is cut to depth and a #3 bit will seat properly rather than bottom out, which matters when you are running a few hundred of them on a driver and do not want cam-out marks on visible flat heads.