Vehicle Fasteners Quiz

Fasteners

• Fasteners are bolts, nuts, screws, clips, and adhesives that hold vehicles together
• Each fastener is designed for a specific application
• Always replace a fastener with the same type as the original equipment manufacturer (OEM) part
• Need to be able to identify and use fasteners properly

Objectives

• Identify different fasteners used on vehicles
• Properly remove and install bolts and nuts
• Explain when specific fasteners are used in vehicle construction
• Explain bolt and nut torque values
• Summarize the use of chemical fasteners
• Identify hose clamps

Bolts

• Bolts have a head on one end and threads on the other
• Cap screws are high-strength bolts
• Bolts are named for the body part they hold (e.g., fender bolt) or by shape and head drive
• Bolt heads are used for tightening the bolt
• Socket wrenches fit over the bolt head
• Improper wrench/socket size can strip or round off the bolt
• This can damage tools or cause injury

Bolt Measurements

• Bolt dimensions (head, grade marking, length, thread pitch, diameter) are needed for work
• Metric and US customary (inch) units are used
• Refer to measurements on diagrams for specific details

Bolts (Continued)

• Bolt length is measured from the threads to the bottom of the head
• Bolt diameter is measured around the outside of the threads
• Head size is measured across the flats
• Common head sizes are 7/16, 1/2, and 9/16 inches
• Common metric sizes are 8mm, 10mm, and 13mm
• Thread pitch is a measurement of thread coarseness
• Bolts and nuts come in coarse, fine, and metric threads
• Bolt threads are measured with a thread pitch gauge
• Do not mix thread types - it damages the part

Bolts (Continued 2)

• Bolts and nuts have right-hand and left-hand threads
• Right-hand threads tighten clockwise
• Left-hand threads tighten counterclockwise
• Left-hand threads have notches or an "L" stamped on them

Bolt Strengths or Grades

• Bolt strength is the tightening force needed
• Bolts are made from different materials with varying hardness
• Bolt grade markings (lines or numbers) on the head indicate strength and hardness
• Metric bolts use a property class indicator on the head to indicate hardness
• More lines on markings represent more strength
• Numerical marking (higher number) indicates more strength in metric bolts

Bolt Strengths or Grades (Continued)

• Bolt strength is indicated by lines (more lines mean stronger) in some systems and numeric values (higher numbers mean stronger) in others
• Tensile strength is the amount of pressure a bolt can withstand before breaking when pulled apart
• Harder bolts have greater tensile strength

Torque

• Torque is the turning force when tightening a fastener
• Over-tightening can stretch or break a bolt
• Under-tightening allows the bolt or nut to loosen and fall out
• Torque specifications are the manufacturer's recommendations for a specific bolt or nut

Torque (Continued)

• Torque wrenches measure torque values
• General bolt torque charts give general torque values for the size and grade of bolt
• Bolt threads should be lubricated for accurate results
• Tightening sequence or torque pattern ensures that parts are clamped down evenly (use a crisscross pattern)

Torque (Continued 2)

• Tighten fasteners in a crisscross pattern
• Tighten fasteners in steps, beginning with half-torque, then 3/4 torque, and then full torque at least twice
• Be careful when using air wrenches as they can quickly damage fasteners.

Nuts

• Nuts have internal threads and an odd head shape, tightened onto bolts
• Castellated or slotted nuts have grooves on top for safety wire or cotter pins
• Castellated nuts are used with studs that hold wheel bearings in position.
• Self-locking nuts produce friction when threaded onto a bolt; the top can be crimped inward

Nuts (Continued)

• Certain locking nuts need to be replaced after removal
• Some front wheel drive spindles use self-locking nuts
• Jam nuts hold larger nuts in place by tightening against another nut, preventing loosening.

Nuts (Continued 2)

• Wing nuts have two arms for hand turning
• Used frequently on parts that need to be removed easily
• Acorn nuts are closed on one end to keep debris and water out
• Body nuts have washers to distribute clamping forces and prevent warpage of the body panel or trim piece

Thread Repair

• Collision repair technicians often repair damaged threads
• Taps are tools for cutting internal threads in holes
• Dies cut threads on the outside of bolts or studs
• Special t-handles fit over taps or dies for turning

Thread Repair (Continued)

• Hold the repair tool squarely when cutting threads
• Lubricating the threads helps prevent wear and tear of the tool
• Back the tool out a little after cutting to remove metal shavings and avoid tool damage
• Helicoils can be used to repair damaged threads

Washers

• Washers prevent damage to surfaces and improve holding power
• Flat washers prevent smaller heads from coming through sheet metal/plastic
• Wave washers create spring action that keeps parts from rattling/loosening
• Body/fender washers have large diameters to have better holding power on thin metal and plastic parts
• Copper/brass prevent fluid leakage

Washers (Continued)

• Spacer washers adjust parts
• Fiber washers prevent vibration/leakage, but cannot be tightened easily
• Finishing washers have curved shapes for appearance
• Split lock washers prevent loosening by vibration
• Shakeproof/teeth lock washers use teeth or bent lugs to hold both the work and nut

Screws

• Screws hold nonstructural vehicle parts
• Machine screws have threads along their full length
• Set screws have an internal drive head for Allan wrenches to hold parts to shafts
• Some sheet metal screws/self-tapping screws have pointed/tapered tips
• Trim screws have washers attached
• Headlight aiming screws may have plastic adapters

Nonthreaded Fasteners

• Square keys, Woodruff keys prevent cams/pulleys turning on their shafts
• Taper pins locate and position matching parts
• Dowel pins position and align parts
• Cotter pins prevent loosening of nuts/bolts
• Snaprings hold parts to shafts, while pop rivets hold sheet metal together

Hose Clamps

• Hose clamps hold radiator and heater hoses in place

Adhesives

• Epoxy is a two-part bonding agent that dries hard and is waterproof and heat resistant
• Trim adhesive is used to install trim pieces to the body and has a rubber-like consistency, bonding plastics, metals, and rubber to painted surfaces.

Summary

• Fasteners (bolts, nuts, screws, clips, adhesives) hold vehicles together
• Bolt strength determines the amount of torque needed
• Nonthreaded fasteners (keys, snaprings, pins, clips, adhesives) do not use threads

Test your knowledge on the various fasteners used in vehicle construction. This quiz will cover the identification, proper use, and torque values of bolts, nuts, and other fasteners. Gain insights into OEM replacement and the application of chemical fasteners in automotive settings.