screws are available in the following material:
Steel - The most common and provides very good rust resistance.
Coated (STALGARD®) - Helps protect ferrous metals from rust and corrosion better
than many conventional finishes.
- Both 18-8 and 410 are available. 18-8 provides excellent corrosion resistance. It can be
mildly magnetic. 410 is stronger than 18-8 and is magnetic. It should be used in a
In addition, a special hybrid
consisting of a hard steel driver fused at mid-body with an 18-8 head provides superior
drilling and excellent corrosion resistance.
- Hex Washer Head - The
built-in washer provides an excellent bearing surface. They can be slotted or unslotted,
although unslotted is most common. The length is measured from under the head.
- Pan Head - This low
profile head can be a phillips or a square drive. The length is measured from under the
- Flat Head - This
countersunk head sinks into wood for a flush finish. The length is measured from the top
of the head.
- Oval Head - A
countersunk base (like a flat head) but with an oval on top for a finished look. The
length is measured from the top of the head.
- Flat Head Reamer - A
flat top and phillips drive ream wood and then cut steel in one operation. Wings ream
clearance hole in thick layers of low density materials to prevent thread engaugement.
When the point penetrates the metal underneath, the wings break off and the threads
engauge normally. The length is measured from the top of the head.
- Round Washer Head -
These are similar to HWH but have a round head with a phillips drive. They are also known
as Metal Lath or K-Lath or Modified
- Truss Screws - The
length is measured from under the head.
- Wafer Head - Also know
as plymetal because they can be used to attach plywood to metal. The large wafer head
sinks into the plywood and has a large bearing surface. The length is measured from the
top of the head.
- Drywall Bugle Head -
These will fasten drywall to metal studs (0.105"). The length is measured from the
top of the head.
- Pan Framing - A
phillips drive stud-framing screw for attaching stud to track. The length is measured from
under the head.
- Pancake Head - A very
low profile head with a large bearing surface. The length is measured from under the head.
- Square Trim -- A square
drive and reduced head for tight spaces. The length is measured from under the head.
S/D/S incorporate similar point
geometry that is found in a standard drill bit. The drill point diameter, angle, web
thickness, rake angle, chisel angle and flute depth assures a fast drill and low pressure
The flute removes the chips that are
generated during drilling. The flute length and depth in conjunction with the drill point
diameter and pilot length determine the thickness of the material the screw is capable of
The length of the pilot section on the
drill point is based on the thickness of the material to be drilled. This unthreaded
portion assures that the drilling action of the screw point is complete before the first
thread engauges the material.
Maximum drilling efficiency is attained
as the screw advances at a rate of approximately 0.004 inches per revolution. Note that
drilling speeds are higher than conventional screws. A speed of 2,500 RPM and a torque
limiting device is recommended. Slower speeds will result in proportionately longer
drilling times. S/D/S must complete the metal drilling function and fully penetrate the
material before the first screw thread engauges. In order to meet this requirement, the
unthreaded length of the screw point (pilot) must be equal to, or greater than, the
material thickness to be drilled. Note that where there is more than one sheet of
material, the calculation of the total thickness to be drilled must include voids or
spaces between sheets.
Once the hole is drilled, the screw
taps the hole in the same way as thread forming or thread cutting screws do in a
pre-drilled hole. S/D/S provide advantages over self-tapping screws into pre-drilled holes
by always drilling the proper hole for optimum fastening, and eliminate torque variations
caused by paint build-up or foreign material in the pre-drilled hole.
A cousin of self-drilling screws is ZIP
or Sharp-Point Screws. These have a very sharp point for penetrating thin sheet metal.
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