72742
Description
Flashcards by Alec Stevens, updated more than 1 year ago
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Created by Alec Stevens
almost 11 years ago
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| Question | Answer |
| Rivets - Solid and Pop/Snap | Rivets permanently join metal. Solid rivets are manufactured from soft iron. They can be countersunk or flat and simply have one end hammered into shape once it has passed through the hole. Pop and snap rivets are pushed through the hole with one end in the rivet gun. The rivet is then compressed and is now too large on the other side to fit back through the hole - the metal is joined. The piece of metal in the gun snaps off and the rivet is left. Solid rivets are extremely out-dated and any rivets at all are now being replaced by spot-welding. |
| Making Nuts and Bolts | Bolts have the thread on them cut by dies, either by hand or lathe in a workshop and by thread-rolling in industry. Using a die requires lubricant, and 1/2 turn clockwise then 1/4 turn anti-clock to free swarf. Danger of the die not being straight! The thread in a nut is cut with a tap, same thing really. Dies and Taps are manufactured from High Speed Steel, which must be harder than the material being threaded. Before cutting a thread with a die, chamfer the edge of the bar to let the die get on the bar. |
| Spacers and Washers | Spacers are used in situations where components need to be separated on a shaft - such as bicycle gears. They can be made from a variety of materials, depending on final usage: HDPE, nylon or steel are all commonly used. Washers can be used as spacers, anti-vibration devices, locking devices and to prevent friction between components. |
| Machine Screws | Machine screws are used for engineering and have parallel sides with standard threads cut into them. Normally manufactured from carbon steel and mass produced. Have a variety of heads or tops including countersunk heads and 'cheese' heads. Countersunk screws are designed to fit into countersunk holes which allow the screw to be flush with the surface of the metal into which is has been screwed. A 'cheese' head is a cylindrical head which is designed to sit above the metal in which it has been screwed. There are also other specialist screws such as grub or set screws which are essentially headless and with the tightening slot machined into the body of the screw. Can have slotted, posi-drive or hexagonal Allen key fit heads. |
| Wood Screws | Wood screws are classified by the shape of the screw head and then by the length of the screw. Unlike machine screws, wood screws are tapered. The heads can be countersunk, raised head and rounded head. A raised head is similar to a countersunk head but slightly domed. A round headed screw is designed to rest on top of the surface. Can have slotted or posi-drive heads. |
| Nuts and Bolts | Usually manufactured from low or medium carbon steel. The advantage is that they can easily be undone and re-done up, meaning that components joined by them can be replaced or repaired. The diameter is always given in millimetres. BS Whitworth thread has a root angle of 55°. ISO metric thread has a root angle of 60°. Nuts have different types of threads depending on what is required, e.g. locking nuts can be used if vibration could be a problem. |
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