Transcript Document
What is a fastener? • A device to locate or hold parts • As a repair technician you will become skilled at removing, reconditioning, replacing, and installing fasteners. • An important skill to learn is how to remove a stuck fastener without breaking it off. • (You will get lots of practice with this as a technician) How do you remove a stuck fastener? • An easy treatment for stuck nuts and bolts is Penetrating Oil (like WD-40). • Some brands work better than others, so ask what works and experiment on your own. • Spray it on the threads and shock or vibrate the fastener (hit it with a hammer) to get the oil to sink in. • You must allow time for oil to work into threads. • I spray and shock a stuck bolt, then go work on another job for an hour or so to let the magic happen Remove a stuck fastener? (After spraying with oil and waiting for it to soak in.) • Use a six point wrench or socket Remove a stuck fastener? (After spraying with oil and waiting for it to soak in.) • You might also use a breaker bar with a 6-point socket • Breaker bars are longer and stronger than ratchets • Never put a pipe on a ratchet handle to get more torque • It will damage the gears in the head of the ratchet Remove a stuck fastener? (After spraying with oil and waiting for it to soak in.) • Use a six point wrench or socket • Try to tighten slightly, then loosen • An impact can help shock the fastener loose • A strong impact will often break off the bolt What about using Vice Grips to remove a stuck bolt? • Vice Grips (locking pliers) damage the head of a bolt or nut and make it MUCH more difficult to remove. • Use Vice Grips to hold or grip objects. • They should never be used as a wrench, or a socket. How do you remove a stuck fastener? • Heat can help loosen a fastener • Too much heat can damage the fastener • Too much heat can weaken the surrounding metal • NEVER heat fasteners red hot When do you use a new fastener? • If it is damaged in any way such as: • corrosion or stretched threads • Always replace Torque to Yield bolts What is a torque to Yield Bolt? • Most commonly used for head bolts • They are tightened (torqued) until they just begin to stretch • This provides a very consistent clamping load and helps keep an even sealing pressure for the head gasket This is how you identify torque-to-yield bolts Torque to Yield bolts require special procedures • Tighten to the specified torque • Continue to turn the fastener just enough to cause it to begin to stretch • This will be specified in degrees of rotation This tool is used so you can see exactly how many degrees you are turning a torque to yield bolt What replacement fastener should you use? • • • • • • Same Length Same Diameter Same Thread Pitch Same Plating or Material Same hardness or GRADE Same weight Bolt Length and Diameter Thread Pitch is measured with a special gauge The correct gauge will match the grooves of the bolt This gauge has a the same thread pitch as the bolt This gauge has a different thread pitch than the bolt Same Pitch Different Pitch These gauges can measure the diameter, pitch and bolt length What replacement fastener should you use? • • • • • • Same Length Same Diameter Same Thread Pitch Same Plating or Material Same hardness or GRADE Same weight Always use the same plating or material as the original fastener • Nuts and Bolts are not all the same. • They must be compatible with the other metals they contact • Many have special plating to resist corrosion • The material or plating will change the general torque (or tightening) value. What replacement fastener should you use? • • • • • • Same Length Same Diameter Same Thread Pitch Same Plating or Material Same hardness or GRADE Same weight Bolt Grade • Bolt Grade is important and easy to identify • A good article on this is at http://www.rockcrawler.com/techreports/fas teners/index.asp Bolt Grade • Both bolt heads marked A are the same grade • Both bolt heads marked B are the same grade • The top are SAE, the bottom are metric • Which bolts are stronger, A or B? When do fasteners have to be the same weight? • Any time the nut or bolt is on a rotating part • Cooling fans • Drive pulleys • Flywheel or clutch or torque converter • Lug nuts Drive shafts Rotating parts • If you replace one fastener on a rotating part… • Replace them all to keep them the same weight • Failure to do this may cause vibration and an unhappy customer How do fasteners lock in place? • Proper torque is usually the only thing that keeps a bolt or nut from vibrating loose • Sometimes lock washers are used, especially when a light fastening torque is desired • Over-tightening a lock washer will ruin it’s ability to hold • Do not any washers unless they were used by the manufacturer How do fasteners lock in place? Cotter pins, locking tabs, and self locking nuts are often used. You should replace these with new ones to ensure they do not fail How do fasteners lock in place? • Thread locking compounds are often used • Two types that are widely available are… Red LocTite© and Blue LocTite© • Use the BLUE unless specified. Using Red LocTite© will make a bolt almost impossible to remove after it the LocTite cures • It is O.K. to use Blue LocTite© for most applications Do not re-use • Cotter pins • Nuts in critical locations such as connecting rod nuts Always use a NEW cotter pin Use new fasteners in highly critical locations like this connecting rod Inspect all self locking nuts Some lock nuts are distorted at the top to create an interference fit. These will wear out after being removed and installed several times Inspect all self locking nuts • Some lock nuts use a nylon insert that may wear out if they are removed and installed too often Inspect all self locking nuts • Self locking nuts should feel tight when the threads of the bolt reach the top of the nut. • If they spin on with little resistance you should replace them with new ones. What do you put on threads? • Anti-seize compound will make it easier to disassemble nuts and bolts • Blue LocTite© will help keep nuts and bolts from vibrating loose • Be sure to clean threads before using LockTite