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Bolts and Fasteners

Bolts and Fasteners. Fasteners are manufactured in a wide range of materials: common steel titanium plastic and other exotic materials. Bolt Identification Bolts are identified by 3 measurements:. Diameter Measured across the threaded area with a caliper or micrometer. Length

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Bolts and Fasteners

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  1. Bolts and Fasteners • Fasteners are manufactured in a wide range of materials: • common steel • titanium • plastic • and other exotic materials.

  2. Bolt Identification Bolts are identified by 3 measurements: • Diameter • Measured across the threaded area with a caliper or micrometer. • Length • Measured from the bottom of the head to the end of the shank • Thread Pitch • (Discussed on the next slide)

  3. Thread Pitch • Thread pitch (English system) • The number of threads per inch • Thread pitch (Metric system) • The distance in millimeters between two adjacent threads

  4. Measuring Thread Pitch – Using a Thread Pitch Guage.

  5. Bolt Grade Markings A bolt’s grade is a measurement of its Tensile Strength • U.S.C. (inch) bolts • Radial lines on the head of the bolt correspond to tensile strength. • More lines represent increasing strength. • Count the number of lines and add 2 to determine the grade of the bolt (ex. 3 lines indicates a Grade 5 bolt).

  6. Bolt Grade Markings A bolt’s grade is a measurement of its Tensile Strength • Metric bolts • Property class numbers on the head of the bolt correspond to tensile strength and yield strength. • The Property Class is expressed with 2 numbers (ex. 10.9). • The 1st number represents the Tensile strength of the bolt (ex. 10 = 1,000 MPa). • The 2nd number represents the percentage rating of the bolt’s Yield strength (ex. 9 = 90% of 1,000 MPa). • Increasing numbers represent increasing strength.

  7. USC Bolt Identification Example • An Imperial size bolt that is identified as 3/8" x 2" x 24: • Has a shank diameter of 3/8 inch. • Is 2 inches long from the bottom of the head to the end of the shank. • Has 24 threads per inch.

  8. Metric Bolt Identification Example • A metric size bolt that is identified as • 6mm x 30mm x 1.00mm: • Has a shank diameter of 6 millimeters. • Is 30 millimeters long from the bottom of the head to the end of the shank. • Has a distance of 1.00 millimeters between its threads.

  9. Key Terms

  10. Torque-To-Yield Bolts • A torque-to-yield bolt must be tightened to its Yield Strength. This means tightening the bolt to a specific torque and then a specified number of degrees (Using a Torque Angle Gauge). • Some Head Bolts are Torque-To-Yield Bolts

  11. Unified Thread Standard The Unified Thread Standard defines a standard thread form and series used commonly in the United States and Canada. Example: • UNC – Unified National Course Thread • UNF – Unified National Fine Thread • A 3/8” UNC bolt has 16 Threads Per Inch • A 3/8” UNF bolt has 24 Threads Per Inch

  12. Unified Thread Standard Other UTS designations include: • UNEF – Unified National Extra Fine • UNPT – Unified National Pipe Thread (used commonly in plumbing and other areas where the threads are used to seal off a liquid) • Oil Drain Plug • Pinion Nut • Engine Coolant Temperature Sensor • Other pipe like things

  13. Thread Sealers and Lockers Thread Sealer Thread Locker • Thread sealers prevent leaks around bolt threads. • Thread lockers such as Locktite prevent bolts from coming loose due to vibrations.

  14. Anti-seize Compound • Anti-seize prevents bolts from getting stuck due to rust and corrosion.

  15. Thread Repair • Threads can get damaged on bolts and nuts from excessive use and from misuse. • A Tap & Die set is designed to create or repair threads.

  16. Tap & Die • A Tap cuts internal threads. • A Die cuts external threads.

  17. Tap & Die Sets There are 3 common types of Taps used by machinists today: • Bottoming Tap - The tap illustrated at the left of the image has a continuous cutting edge with almost no taper. A bottoming tap is used on holes that already have threads.

  18. Tap & Die Sets • Intermediate Tap - The tap illustrated in the middle of the image has tapered cutting edges, which assist in aligning and starting the tap into an untapped hole

  19. Tap & Die Sets • Taper Tap - The small tap illustrated at the bottom of the image is similar to a plug tap but has a more pronounced taper to the cutting edges. This feature gives the taper tap a very gradual cutting action that is less aggressive than that of the bottoming tap.

  20. Bolt Extraction • Broken bolts have to be removed before the threads can be repaired. • Bolt Extractors are tools designed to remove broken bolts.

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