Hilti Product Technical Guide Vol 1 Direct Fastening - page 158

3.6.1 Self-DrillingScrew Fastener SelectionandDesign
Screw Fastening Systems
158
Hilti, Inc. (US) 1-800-879-8000 |
I en español 1-800-879-5000 I Hilti (Canada) Corp. 1-800-363-4458 I
I Direct FasteningTechnical Guide 2015
L
MF
T
3.6.1.4SealingCriteria
Sealingwasher screwsofferweather resistant fastenings
wheremoistureor condensation is a factor. Thewasher helps
seal thehole tohelppreventmoisture fromdripping into the
fastener threads from the fastenedmaterial side, reducing
corrosivebuild-up. As addedprotectionagainst corrosion,
all sealingwasher screws come standardwithKwik-Cote
coating. The torquecontrol or depthgaugeof theelectric
screwdrivers helpensure that theoptimal seal is applied
(ReferenceSection3.6.1.7).
3.6.1.5 LengthSelection
Lengthof the screw (L)
Dependingon the screwhead, thereare twodifferentways to
measure theoverall lengthof a screw.
For HWH
/
HHWH, PPH, PTH, PFTH, SHWHandPPCH screws,
theoverall length ismeasured from thebottomof thewasher
under thehead to thepoint of the screw.
For PWH, PFH, PBHandPFHUC screws, theoverall length is
measured from the topof thehead to thepoint of the screw.
MaximumTotal Thickness (MT)
Themaximum total thickness (MT) for all screws is the length
of the threads reducedby the first three threads (protruding
past theback-sideof thebasematerial). Seedrawings above
andbelow.
Themaximum total thickness (MT) describes themaximum
thicknessof all attachments tobe fastenedplus the
basematerial.
3.6.1.3HeadStyleSelection
HWH (HHWH)
(High) HexWasher
Head :Washer face
provides abearing
surface for thedriving
sockets.
PPH (PPFH)
PhillipsPan
(Framing) Head:
Conventional head for
general applications
andprovides low
profile fastening.
PFH
Phillips Flat Head:
Usedprimarily in
wood to countersink
and seat flushwithout
splintering thewood.
PWH
PhillipsWafer Head:
Large headprovides
thebearing surface
necessary to seat
flush in softmaterials.
PBH
PhillipsBugleHead:
Usedprimarily for
fasteningdrywall,
plywoodor insulation
board to steel studs.
PTH (MPTH)
(Modified) Phillips
TrussHead: Large
headand lowprofile
provides surface area
needed to attachwire
lath tometal stud.
PPCH
PhillipsPancake
Conventional Head:
Head for general
applications and
provides low and
flat profile.
PFTH
Phillips Flat Truss
Head: Lowest profile
head available for
attachingmetal
tometal.
PFHUC
Pancake Framing
HeadUndercut: Used
for countersinking
where a full head
taper would cause
stand-off of the screw.
SHWH
SlottedHexWasher
Head: Hexwasher
headwith slot in
center toprovide
additional drive
connection.
L
MF
MT
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