3.6.1 Self-Drilling Screw Fastener Selection and Design
Screw Fastening Systems
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I en español 1-800-879-5000 I Hilti (Canada) Corp. 1-800-363-4458 I
I Direct Fastening Technical Guide 2013
18.104.22.168 Sealing Criteria
Sealing washer screws offer weather resistant fastenings
where moisture or condensation is a factor. The washer helps
seal the hole to help prevent moisture from dripping into the
fastener threads from the fastened material side, reducing
corrosive build-up. As added protection against corrosion,
all sealing washer screws come standard with Kwik-Cote
coating. The torque control or depth gauge of the electric
screwdrivers help ensure that the optimal seal is applied
(Reference Section 22.214.171.124).
126.96.36.199 Length Selection
Length of the screw (L)
Depending on the screwhead, there are two different ways to
measure the overall length of a screw.
HHWH, PPH, PTH, PFTH, SHWH and PPCH screws,
the overall length is measured from the bottom of the washer
under the head to the point of the screw.
For PWH, PFH, PBH and PFHUC screws, the overall length is
measured from the top of the head to the point of the screw.
Maximum Total Thickness (MT)
The maximum total thickness (MT) for all screws is the length
of the threads reduced by the first three threads (protruding
past the back-side of the base material). See drawings above
The maximum total thickness (MT) describes the maximum
thickness of all attachments to be fastened plus the
188.8.131.52 Head Style Selection
(High) Hex Washer
Head : Washer face
provides a bearing
surface for the driving
Conventional head for
and provides low
Phillips Flat Head:
Used primarily in
wood to countersink
and seat flush without
splintering the wood.
Phillips Wafer Head:
Large head provides
the bearing surface
necessary to seat
flush in soft materials.
Phillips Bugle Head:
Used primarily for
plywood or insulation
board to steel studs.
Truss Head: Large
head and low profile
provides surface area
needed to attach wire
lath to metal stud.
Head for general
provides low and
Phillips Flat Truss
Head: Lowest profile
head available for
Head Undercut: Used
where a full head
taper would cause
stand-off of the screw.
Slotted Hex Washer
Head: Hex washer
head with slot in
center to provide