FALL 2023

THE DISTRIBUTOR’S LINK 173
BRUNO MARBACHER THREAD-CUTTING SCREWS AND SELF-DRILLING SCREWS FOR SPECIAL APPLICATIONS from page 172
The cold-headed drill points are sharp. This point
prevents a spiral wandering off, when it is placed
slightly off-angle. The drilling process can be started
easily.
However, if the point has a small web (chisel edge -
similar to drills), the rotating point will wander off when
it is placed on the work piece. The “web” is practically
only found in very long, milled drill points, which are too
long to be cold headed.
Self-drilling screws are useful for drilling a wide range
of materials like metal sheets, aluminum, stainless
steel, wood and timber. They are widely used for
electrical, insulation, roofing, construction, cladding
and HVAC applications.
Self-Drilling Screws With Wings
The self-drilling screw with a long drill point and
wings is called the wing-teks screw.
Wing-teks screws are installed in multiple steps, At
first the point drills through the wooden board. Next
the bore-wings enlarge the drilled hole up to the thread
diameter. Thus, the screw thread can rotate freely in
the wood.
The underside of the screw’s head is furnished with
reaming cutters, they mill a countersink into the soft
wood so that the head of the screw is flush with the
surface of the wood.
The Wing Teks® screws are used to fasten timber
floors, fences and composite boards to metal.
Self-Drilling Screw Materials And Mechanical
Properties
Self-drilling screws are usually made of case-hardened
steel. They may also be made of 410 Stainless Steel.
This is to ensure that the drill point is harder than the
metal it’s going into. 410 Stainless Steel is ideal for
self-drilling screws because it maintains the corrosion
resistant properties of Stainless steel but can be
heat-treated up to a hardness of 40 HRC. Material,
mechanical and drilling properties of self-drilling screws
are covered in ISO 10666, and SAE J78
Self-drilling screws made of 300 series austenitic
stainless steel A2 (AISI 304) get their hardness through
intense strain-hardening. For this reason, they can only
be assembled into aluminum parts.
Marutex screws are special self-drilling screws made
of stainless steel. Marutex screws are made with a
special material that has 2% molybdenum added to
410 stainless. Molybdenum is a significant component
of AISI 316 (A4) stainless steel that provides extra
corrosion resistance.
The hardness permits drilling through steel without
problems.
The drill point then makes contact with the metal
part and drills a pilot hole in it. The 2 bore-wings are
sheared off when they make contact with the metal
frame. Now the screw thread can form its mating thread
in the metal frame.
In Conclusion
What screws works best for a given application,
has to be established through application testing.
Consulting with an application engineer will help setting
up appropriate design parameters and installation
procedure.
BRUNO MARBACHER