5Bolts The most common threaded fastener Many variations Uses either a metric or standard thread pitch measured in threads per inch or millimetersThe bolt size is its diameter.Hex size is the wrench size.Length is measured from hex to threaded end.Bolt grade markings are on the top of the hex.
9Bolt SizeThe size of the bolt is the diameter of the shank of the bolt.Metrics in millimeters.Standards in fractions of an inch.
10Bolt LengthThe bolt length is the distance from the hex head to the end of the thread.
11Thread Pitch Two general types of bolts used. Standard fractional inch sizes.Metric millimeter sizes.Look at the top of the hex head to tell the difference.
12Thread Classification UNC-United National CourseUNF-United-National FineNPT-National Pipe ThreadMetric
13Bolt DesignationsFirst item is bolt size which is the same as the bolt diameter.Second item is the thread pitch.Third is bolt length.
14Measuring Thread Pitch The pitch gauge has teeth much like the threads. Put the gauge that fits into the threads and read the number on the gauge.Standards in threads per inch.Metrics in threads per millimeters.
15Hex Head SizesMetricThis is the size wrench that will be needed to install or remove a bolt.Pay attention to metric or standard.Torque to proper amount.Standard
16Studs Studs look similar to a bolt but have no hex head for a wrench. One end screws into an engine part and the other holds a different part on with a nut.
20Cotter pins are used to secure nuts to shafts so they don’t come loose. Often used with a castle nut.Cotter Pins
21Snap RingsSnap rings are used to secure bearings, gears, and linkages.
22Torque WrenchesTorque wrench measure how much you are tightening a bolt.Bolts can only take so much torque or they break off! That’s a bad thing.
23How Much Torque?The amount to torque a bolt depends on two important items.1 – The diameter of the bolt. (the fatter the stronger)2 – The grade of the bolt. (the better the grade the more torque it can take)
24Bolt Torque ChartsThese are found in repair manuals, service manuals and on computer data systems.Torque Sequence
25Thread LockCompounds such as Locktite literally glue the threads so they don’t vibrate loose.
26Anti-Seize CompoundsInhibits the threads from rusting up and totally jamming together.