4NUTS AND BOLTS.A bolt is a metal rod with external threads (outside) on one end and a head on the other.When a bolt is threaded into a part without a nut it is called a cap screw.A nut has internal threads (inside) and usually a hex(6 sided) outer shapeWhen a nut is screwed onto a bolt a powerful clamping force is produced.
5IN AUTOMOTIVE TECHNOLOGY Nuts and bolts are named after the parts they hold. For example “head bolts” these bolts obviously hold the cylinder head to the engine block.Can you tell me what the bolts that connect the piston ROD to the crankshaft are called?That’s correct they are called ROD bolts.
6NUT AND BOLT TERMINOLOGY. Nuts and bolts come in a wide variety of sizes and grades (strength) and thread types.It is important to understand the differences.The most important bolt dimensions are.Bolt size, bolt size is the measurement of the outside diameter of the bolt threads.
7TERMINOLOGY CON’TBolt head size, is the distance across the flats or outer sides of a bolt headIT IS THE SAME AS THE WRENCH SIZE!Bolt length, is measured from the bottom of the bolt head to the threaded end of the bolt.Thread pitch, is the distance between the threads of a bolt.With U.S. fasteners it is the number of threads per inch.With metric fasteners it is the distance between the threads in millimeters.
9THREAD TYPES.There are three basic types of threads used on fasteners.COARSE THREADS (UNC unified national coarse)FINE THREADS (UNF Unified national fine)METRIC THREADS (SI)
10Never interchange thread types or thread damage will result!
11Different thread directions Bolts come in right hand thread of left hand thread.No this does not mean that you have to use your left hand to turn a left handed bolt.This simply means that one turns to the right to tighten and one turns to the left to tighten.Left thread fasteners are identified with a capital (L) on their heads
13BOLT GRADESBolt grading or tensile strength refers to the amount of pull of stretch a fastener can withstand before breaking.Tensile strengths can vary, bolts are made of different metals some stronger than others.
14BOLT HEAD MARKINGSAlso called grade markings specify the tensile strength of a bolt.COVENTIONAL BOLTS, are marked with lines or slash marks.The more lines the stronger the bolt.METRIC BOLTS, are marked with a numbering system.Yes you guessed it the larger the number the stronger the bolt.
16DANGER! PELIGRO!NEVER REPLACE A HIGH GRADE BOLT WITH A LOW GRADE BOLT.THE WEAKER BOLT COULD EASILY SNAP CAUSING PART FAILURE AND A VERY DANGERIOUS SITUTATION!
17BOLT DESCRIPTIONA bolt description is a series of numbers and letters that describe a bolt.These numbers and letters are needed when buying a new bolt.For example M-20x2.00x50-8.8This is a description for a metric bolt.
18Bolt Description The M tells us that it is a metric thread bolt. The 20 tells us that what the diameter of the threads in millimeters is.The 2.00 is the distance between the threads in millimeters. (this is referred to as THREAD PITCH)The 50 tells us the length of the bolt in millimeters.Lastly the 8.8 tells us how strong the bolt is or it’s tensile strength.
20NUT TYPES Many types of nuts are used in the automotive field. The most common are shown below
21COTTER PINS AND WASHERS First a cotter pin is a safety device normally used in a slotted nut.It keeps the nut from turning and coming off.Washers are used under bolt heads and nuts.There are two basic types of washers Flat and Lock.
22WASHERS FLAT WASHERS, Increase the clamping force of a bolt or nut. LOCK WASHERS, Prevent the bolt or nut from coming loose under stress and vibration.LOCK TABS OR PLATES, perform the same function as flat washers and lock washers.They increase clamping surface area and secure the fastener.
23TORQUEING BOLTS.It is very important that nuts and bolts be tightened properly.If OVERTIGHTENED, a bolt could stretch and possibly break, the threads could also fail.If UNDERTIGHTENED, a bolt could work loose and fall out.Part movement could also shear the bolt in two or break a gasket.
24TORQUE SPECIFICATIONS Also called “TORQUE SPEC’S” are tightening values given by an auto manufacturer.They are normally given for all precision assemblies.Such as CYLINDER HEAD TO BLOCK.TRANSMISSION TO ENGINE
25USING A TORQUE WRENCH.When using a torque wrench follow these basic rules.1) Keep a steady pull on the wrench. For accuracy do not use short jerky pull motions.2) clean and lightly oil the fastener threads.3) When possible avoid using swivel joints.they can upset torque wrench accuracy.4) When reading a beam type torque wrench look straight down at the scale looking from an angle can give a false reading.
26TORQUE WRENCH.5) A general torque reading chart should only be used when manufacturer’s specs are NOT available.6) When manufacturer’s torque patterns are not available, use a general crisscross pattern.7) pull only on the handle of a beam type torque wrench do not let the beam touch anything.
27THERE IS A LOT TO KNOW ABOUT HOW TO USE A TORQUE WRENCH 8) Retorque when required, on some assemblies like cylinder heads, intake manifolds and exhaust manifolds, the bolts may have to be retightened after reaching operating temperature.
28THREAD REPAIRSA technician must be able to repair damaged threads quickly and properly.Threaded holes can be damaged requiring repairs.
29MINOR THREAD REPAIRSMinor thread damage includes partial flattening and other less serious problems.Minor thread damage can usually with a thread chaser or threading tool.
30MAJOR THREAD REPAIRS Major thread damage generally includes Badly smashed threads, striped threads or threads that can not be repaired easily.Sometimes major thread damage is repaired with either a tap or die.
31TAPS A tap is a threaded tool. Used for cutting threads into a hole. Various tap shapes are provided.Some are used for starting the threads others for cutting threads down to the bottom.
32DIES A die cuts an external thread It can be used to cut threads on metal rods.It can also be used to cut threads on bolts, shafts and pins.
33TAP AND DIE RULES NEVER FORCE a tap handle or the tool could break. For every one turn you must back off ¼ turn to clean out the metal shavings.Keep taps and dies well oiled to ease the cutting process and prolong tool life.Always use the correct size tap in a correctly sized drilled hole.Use coarse threads when threading into soft metal such as aluminum, coarse threads will hold better than fine.
34THREAD REPAIR INSERTA thread repair insert is a coil of metal that when inserted into a hole will bring that hole back to the manufacturers specifications.They are used where an oversized hole would be unacceptable.A good example of this would be a car that is being restored original condition.
35SHEET METAL SCREWS.Sheet metal screws are commonly used to hold plastic and sheet metal parts.Sheet metal screws have tapering threads that are widely spaced.Sheet metal screws come in a wide variety of head shapes, sizes and screwdriver head sizes.
36NON THREADED FASTENERS. Numerous types of non threaded fasteners are used in the assembly of an automobile.It is important that you learn the most common types.
37SNAP RINGSA snap ring fits into a groove in a part and holds one part into another.There are two types of snap rings.INTERNAL and EXTERNAL
38KEYS AND KEYWAYSA metal key fits into a keyway (groove) cut into a shaft and part.The key prevents the part from turning on its shaft.SET SCREWS are used to lock a part onto its shaft.They can be used with or without a keyway.
39SPLINESSplines are a series of slots cut into a shaft and a mating part.Splines have one advantage over a key splines allow the part to slide over the shaft but still not rotate.This sliding lock system is commonly used in transmissions and driveshafts.
40ADHESIVESAdhesives (special glues) are widely used on modern automobiles.They hold everything from emblems to nuts and bolts together.Some are designed to stay soft and pliable.Others dry hard some take hours to dry while others take minutes.
41GASKETS AND SEALS.Gaskets and seals are used between parts to prevent leakage of various fluids.Such as engine oil, coolant, transmission fluid and other fluids.It is important to understand a few principles about gaskets and seals.If they are serviced improperly mechanical failures can result!
42GASKETSA gasket is a soft, flexible material placed between two parts to prevent leakage.It can be made of many different materials such as rubber, neoprene, cork, treated paper or thin steel.When the parts are fastened together the gasket is compressed and deformed.This forces the gasket to fill any imperfection in the parts so there is no leakage.
43GASKET RULES When working with gaskets remember the following. Inspect for leaks before disassembly, if two parts are leaking they should be inspected for defects before reassembly.Avoid part damage during disassembly. Be careful not to gouge, nick or scratch any imperfection could cause a leak.Clean off old gasket carefully all of the old material must be remove from the old parts.
44SealantsSealants are commonly used with gaskets to prevent leakage or to hold the gasket in place.
45Sealants Shellac -65 to 350F -54Cto 177C General assembly TypeTemperatureRangeUseResistanttoShellac-65 to 350F-54Cto 177CGeneral assemblyGaskets of paper, felt,cardboard rubber metalGasoline,kerseneHardeningGasket Sealant-65 to 400F-54C to 205CPermanent assembliesFittings threaded connections and for filling uneven surfacesNon HardingSemi permanent assemblies cover plates flanges threaded assemblies hose connections and metal to metal assemblies
46Two Types of SealersHardening sealers are used on permanent assemblies such as fittings and threads.They are resistant to heat and most chemicals.Non hardening sealers are used for semi permanent assemblies such as cover plates, flanges, threads, hose connectors they are resistant to most chemicals.
47Form in place GasketsThese are special sealers that are used instead of gaskets.Two types of form in place gaskets are RTV and anaerobic sealer.RTV (room temperature vulcanizing) is a silicone based sealer that cures or dries in the air in other words it needs the moisture in the air to dry!