S - Bolts to Adhesives Flashcards
parts of a threaded fastener system
- BOLT
- NUT
- WASHER
- possibly additional anti-loosening features
how can the TORQUE/TENSION relationship be made predictable and independent of the specific workpiece?
a WASHER
what are the reasons for placing a WASHER between the nut and workpiece?
- to provide a predictable surface upon which the nut can slide
- spreading load
- to cover a hole
- protect the clamped surface from maring
an oversized variant of the PLAIN/FLAT WASHER
FENDER WASHERS
relies solely on friction to remain tight and may loosen in service as a result of vibration
THREADED FASTENING
a type of ratcheting LOCK WASHER with a ratcheting design, a ring of hardened spring steel is split, and the ends are displaced vertically to create a single-turn helical geometry. the washer is flattened when compressed between surfaces during tightening.
SPLIT WASHER
can SPLIT WASHERS be reused
yes, but it may be advantageous to reassemble with the nut turned the other way up if a plain nut is used
when using a SPLIT WASHER, what is the visual warning that the joint has loosened
if you can see the SPLIT WASHER in its uncompressed form during service
a type of ratcheting LOCKING WASHER that is available in both internal and external forms, inexpensive, mostly on small joints, tend to flatten permanently when compressed
TOOTHED WASHER
can TOOTHED WASHERS be reused?
no, they are ONE-USE ONLY
LOCK WASHERS that attempt to increase friction and bolt tension through compression of shaped (non-flat) discs (3)
- CURVED
- WAVE SPRING
- BELLEVILLE (can be stacked to customize compressive force)
a vital part of a BOLTED JOINT (not the bolt)
NUT
the 2 basic types of NUTS
- NON-LOCKING
- LOCKING
the simplest type of NON-LOCKING NUT which consists of a multi-sided cylinder with a central tapped hole, generally HEXAGONAL
PLAIN NUT
another shape that non-locking nuts can come in, still fit in the parallel jaws of a standard open-eyed wrench, mainly used in conjunction with T-SLOTS on machine tables
SQUARE NUT
NUTS primarily used on WATER HYDRANTS in an anti-tamper role
PENTAGONAL
a type of plain nut intended to be tightened by hand only, but they can be tweaked by placing a screwdriver shaft diagonally between the wings (not recommended)
WING NUT
a type of nut that employs a blind threaded hole, mainly for decorative use, or as a safety feature to guard the exposed end of a stud on rotating equipment, difficult to use
BLIND NUTS
different names for BLIND NUTS (3)
- DOME
- ACORN
- LUG (when used on car wheels)
a type of nut that uses a unique design that allows the nut to be placed on a threaded rod from the side rather than threaded all the way from the end
SLIP-ON NUT
a slimmer version of a plain nut, tightening this nut against another plain nut can provide extra security
JAM NUT
a common type of LOCK NUT which is basically a plain nut with a captured ring of plastic stacked on top
NYLOC NUT/ NYLON INSERT LOCK NUT
what happens when the specific polymer NYLON is exposed to moisture through atmospheric humidity?
it swells and squeezes the plastic tighter against the threads.
are NYLOC NUTS reusable?
no they are ONE-USE-ONLY
what limitations come with using a NYLOC NUT?
NYLOC NUTS can only be put on one way around, but are also restricted to fairly low temperature use
2 types of nuts that both integrate ratcheting washers into their design, restricted to one-way application, quickly spin on, not limited by temp, not much more effective than using plain nut and lock washer combo
- FLANGE NUTS
- KREPS-K-LOC NUTS
nuts that have had the threads deformed to greatly increase friction
- CENTER LOCK NUTS (dented on one flat)
- DISTORTED NUTS (with lobular deformation of the top threads)
- MARSDEN NUTS (free spinning, but the fingers created by thin slits tend to bend inward when heavily torqued during final tightening)
nuts designed to be used in conjunction with a COTTER (SPLIT) PIN
CASTLE (SLOTTED) NUTS
what is routinely done to ensure absolute safety and accountability
- split type lock washers are installed
- thread-locking adhesive to stop vibration loosening
- safety wire
- metal tags attached to the safety wire (accountability)
machine screws that don’t have a head, a short threaded rod with some means of being driven at one end, and a gripping surface at the other end
SET SCREWS/BLIND SCREWS/GRUB SCREWS (outside the U.S.)
without a head, these can be driven below flush with a surface and are used mainly for light-duty applications
SET SCREWS
the most common driver
ALLEN (HEX SOCKET)
other types of drivers available
- SLOTTED
- PHILLIPS
- TORX
- TAMPER PROOF
screws that don’t develop much tension and rely primarily on friction with the underlying surface to remain secure
SET SCREWS
one example of a mechanical fastener system, basically a heavy-duty version of that used to bind paper sheets together, mostly seen on cardboard packing cartons
METAL STAPLING/STITCHING
an example of a mechanical fastener system that relies on elastic flexing and cunning “one-way” design
SNAP-FIT FASTENING
one modern unique type of fastener commonly known as VELCRO
HOOK & LOOP
a modern fastener that has a 2 part system with both parts being constructed on a fabric backing
CLOTH HOOK & LOOP
advantages of VELCRO
- perfect closure of backpack, shoes, clothes
- light
- fast to use
- micro-adjustable
disadvantages of VELCRO
- noisy
- wear out over time
how do you separate VELCRO
a force must be applied greater that the holding force
a heavy-duty industrial use fastening system; conceptually it is a HOOK & LOOP design, and its functionality borrows heavily from SNAP-FIT technology
STEEL VELCRO
a fastening system that addresses the problem of easy removal by employing “shape memory alloy” for the hooks
ELECTRO-ACTIVE VELCRO
used to BOND (stick) two surfaces together, very broad and diverse JOINING method
ADHESIVES (glues)
name an advantage that other JOINING METHODS like BOLTING, RIVETING, and WELDING, ADHESIVE BONDING
- smooth uninterrupted surface
- no stress concentrations
- vibration and sound dampening
- sealing against fluid intrusion
con cope with complex geometries - can join materials of different composition
- lightweight
- no damage to heat-sensitive materials
- no holes or loss of material integrity
name is a disadvantage that other JOINING METHODS like BOLTING, RIVETING, and WELDING, ADHESIVE BONDING
- takes time to reach full strength
- need for meticulous surface preparation
- low peel strength & susceptible to creep
- poor heat resistance
- poor resistance to solvents
- inflammability
- toxicity during assembly & Disposal
- damage from humidity, UV, and microbes
- not easily disassembled
5 examples of different forms of ADHESIVES:
- paste (mastic)
- liquid
- tape
- powder
- solid (sticks)
STEPS 1 of the SURFACE PREPARATION PROCEDURE
SCUFF/ABRADE the adherend surface to remove oxidation or loose material and rough up the surfaces to provide a better BITE for the adhesive
in STEP 1 of the surface preparation procedure, what is used to pick up debris rather than blowing it off with the risk of it resettling on the surface
TACK CLOTH
STEP 2 of the surface preparation procedure
DEGREASING with a solvent to remove films and oily contaminants, not the same as cleaning which may leave a residue
5 examples of flavored solvents used for DEGREASING
- DENATURED ALCOHOL
- ACETONE
- MINERAL SPIRITS
- PAINT THINNER
- TURPENTINE
STEP 3 of the surface preparation procedure involves making sure the environment around the work area is well-ventilated and that PPE is worn
CURING MECHANISM
5 types of CURING MECHANISMS
- SOLVENT- cures as moisture evaporates away
- CHEMICALLY REACTIVE- cures as two components are mixed together
- HOT MELT- heat activated
- UV CURE- exposed to ultra-violet light
- PRESSURE ACTIVATED- d by applying physical pressure, almost immediate
4 examples of common ADHESIVE types:
- SUPERGLUE/CRAZY GLUE, technically known as CYANOACRYLATE
- EPOXY
- ANAEROBIC THREAD LOCKER (loctite)
- CAULK
marketed for its instant curing ability, not a particularly strong adhesive especially in shear and on smooth surfaces
SUPER GLUE
standard SUPERGLUE is mildly toxic, but this can be reduced by using a medical formulation based on 2-octyl cyanoacrylate
DERMABOND
known as a TWO-PART adhesive, since it requires two liquid chemicals to be combined together, a STRUCTURAL ADHESIVE
EPOXY
what are the 2 types of liquid chemicals combined in EPOXY
RESIN and HARDENER
ADVANTAGES of EXPOXY (5)
- very strong
- adhere to virtually any material
- can cure underwater
- very stable and resistant to heat, moisture, and many chemicals
- show very little creep
DISADVANTAGES of EPOXY ()
- poor toughness, prone to shattering under impact
- doesn’t cure instantly
- the faster the cure time the lower the strength
- joints must be immobilized until handling cure is reached
adhesive that cures in the ABSENCE OF OXYGEN and requires CONTACT WITH A METAL, comes in various strength grades for any given fastener configuration
ANAEROBIC/THREAD LOCKER
a special type of low-strength adhesive, ELASTOMER that provides flexibility rather than strength, used as a SEALANT to prevent fluid intrusion in bathtubs or along chimney flashing.
CAULK
CAULK formulations can be based on: (4)
- LATEX
- SILICONE
- URETHANE
- ACRYLIC
factors to consider the choosing a CAULK (6)
- adhesion to various materials (including wet surfaces)
- expansion coefficient
- UV resistance
- drying/cracking
- yellowing
- cleanup/removal
