Threads and Fasteners

Purpose Machine screws Locking pins Adhesives Keys To fasten objects together Common Fasteners: Nuts & bolts Tapers Rivets Screws Nails Machine screws Locking pins Adhesives Keys

Threads Course Threads, Fine Threads, Metric threads and whitworth. Course and fine are common imperial Metric is common Whitworth is the old British standard

Course Threads Threads farther apart Deeper cut Best used with soft materials Aluminum Brass Copper Plastic

Fine Threads Threads closer together More thread contact for length Common in harder metals

Metric Has similar course and fine types Measured differently Different head markings

Whitworth Threads Only found in old British cars 55° thread instead of standard 60 °

Thread classification UNC Unified national course UNF Unified national fine Standard measurement Measured in threads per inch Metric Measured by the distance in mm between the treads

Measuring Bolt Size = Major Diameter Bolt head size = Distance between the flats of the hexagon

Measuring Bolt length = the distance from the base of the head to the end of the thread Thread pitch = Threads per inch & Distance between threads

Grade Tensile strength (pulling strength) Amount of PSI the bolt can handle Only accurate for bolts with a 1 inch diameter

Grade Grade stamped on top Imperial grade = number of lines + Two Metric Grade is printed 5D, 8G, 10K, 12K.

Under load When a bolt goes past its load capacity it reaches its elastic limit After elastic limit the bolt stretches and looses strength

Torque Specs All bolts on a vehicle have a special specification that they have to be tightened too. Always look this up in the manual before tightening any thing

Flat Washers Used to make larger bearing surfaces for nuts to ride on Stops nuts and bolts from becoming imbedded in soft materials

Lock Washers Prevents fastener from loosening Made from spring steel Split and bent, cuts in to base material and fastener

Multiple Tooth Washer Solid piece Has twisted teeth that dig in to fastener and base metal

Pins Retains parts in a fixed position Used for alignment

Cotter Pins Used to hold nuts in position Specifically Castle nuts

Snap Ring Clips in to groves to retain parts Groves can either be external or internal

Keys Used to fix gears and pulleys to shafts Cut in gear or pulley called the key seat Cut in shaft called the key way

Adhesives Liquid or semi-liquid Prevents loosening Only one drip Range from light to strong

Sealants Resistance from the elements Oil, water, gas, grease, and salt