Presentation is loading. Please wait.

Presentation is loading. Please wait.

Topics Introduction Terminology Thread Specifications Bolts and Screws Nuts and Locking Devices Exercise Questions Note: Refer to Chapter 6 in the text.

Similar presentations


Presentation on theme: "Topics Introduction Terminology Thread Specifications Bolts and Screws Nuts and Locking Devices Exercise Questions Note: Refer to Chapter 6 in the text."— Presentation transcript:

1 Topics Introduction Terminology Thread Specifications Bolts and Screws Nuts and Locking Devices Exercise Questions Note: Refer to Chapter 6 in the text. 1 MECH 1200

2 Introduction There are two thread standards: – The Unified Screw Thread Standard: Used in the U.S. It is based on a 60 o thread angle. Unified National Coarse (UNC) series: this is the most common series. Bolts, screws, and nuts of this series are used for general applications in which a quick assembly is required. Unified National Fine (UNF) series: threads of this series are used for handling high tensile stresses, or when the length of engagement is limited such as screws in thin walls. Unified National Special (UNS) series – The International Screw Thread Standard: most common standard, based also on the 60 o thread angle. 2 MECH 1200

3 Terminology – Thread angle: the angle included between the sides of the thread, The ISO thread angle is 60 degrees. – Pitch: the distance between one point on a thread to the corresponding point on the next thread. – Number of threads per inch – Minor (root) diameter – Major (Outside) diameter – Lead: the distance a screw thread advances in one revolution. -Thread Fit: How tight is the thread engagement. Three classes of fit are used in the unified system, loose, medium, and tight fits. A for external and B for internal fits. (see p. 110) 3 Source: Siemens Technik Akademie Berlin MECH 1200

4 4 Thread Specifications Source: Siemens Technik Akademie Berlin MECH 1200

5 Carriage Boltused to fasten metal to wood. It has a square body right under the head to keep the wood from turning. Machine Screwused for vehicle body and metal sheets Sheet Metal Screwused for vehicle body and metal sheets Set Screwusually has no head, used to lock pulleys or gears to shafts Socket Head Screwhas the strongest head style 5 Common Bolts and Screws MECH 1200

6 6 Stud (Standing) Bolthas threads on both ends, screwed permanently in one end and a nut on the other end. Hexagon Through Bolt Hexagon Fit Bolt If the bolt goes through all parts and is fastened with a nut, then it is called a Through Bolt. When used to fix a part in position against movement it is called a Fit Bolt. Anti-Fatigue BoltHas a reduced shank, used for applications in which shock loads occur. Source of images in this slide: Siemens Technik Akademie Berlin MECH 1200

7 Nuts 7 Cap (Acorn) Nut Wing nuts Hex nuts: Have a hexagonal shape, and has different grades Castle Nut: Named so because it looks like a castle, used in applications where heavy vibrations occur, such as on wheels. Can handle light torques.only. MECH 1200

8 8 Fastener Locking Devices Spring lock washer Split pins Safety wires External tooth lock washer -Screw locking devices are used to keep the nut from getting loose. -They can be friction based or non-friction based: Lock washer Internal tooth lock washer Tab washer Nut lock plate Friction based Locking devices Non-Friction based Locking devices MECH 1200

9 Exercise Questions 1.What are the two thread standards? The Unified Screw Thread System and the ISO metric thread standard. 2.Thoroughly describe the bolt given by: ¼ - 28 UNF 2A The bolt has an outer diameter of ¼ inch and a fine thread of 28 threads per inch (Unified National Fine thread series) and has a medium fit with external thread. 3.Thoroughly describe the thread bolt given by: M10 x 1.25 The bolt is metric and its outer diameter is 10 mm and has a pitch of 1.25 mm 9 MECH 1200

10 3.If a thread has 40 threads per inch what is its pitch? Pitch = 1 inch / 40 = Is each of the screw locking devices below friction based or not? 10 YesNo Yes No MECH 1200

11 3.What is the component shown in the figure below? Castle Nut: used in applications that require low amount of torque, and where vibrations are common. 11 MECH 1200


Download ppt "Topics Introduction Terminology Thread Specifications Bolts and Screws Nuts and Locking Devices Exercise Questions Note: Refer to Chapter 6 in the text."

Similar presentations


Ads by Google