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 Be sure to use Impact sockets not chrome! 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
What replacement fastener should you use? Metric or U.S. Same Length Same Diameter Same Thread Pitch Same Plating or Material Same hardness or GRADE Same weight
Bolt Length and Diameter U.S. = Inches Metric = Millimeters
Thread Pitch is measured with a special gauge U.S. = TPI Metric = Thread Pitch TPI stands for Threads Per Inch. This is simply a count of the number of threads per inch measured along the length of a fastener. TPI is used only with American (U.S.) fasteners. Metric fasteners are specified with a thread pitch instead of a thread count. The thread pitch is the distance between threads expressed in millimeters (measured along the length of the fastener). For example a thread pitch of 1.5 means that the distance between one thread and the next is 1.5mm.
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
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 Lubrication on threads will change the published torque value!
Proper Torque is critical Torque is the twisting force applied Too low of a torque will allow a bolt to fall off Too high a torque may stretch a bolt Unequal torque may distort or warp the parts being clamped together