User:Shivprasad vilas gite/sandbox

hi i am shivprasad Machine screws are generally stronger than wood screws, have finer threads and are made more precisely. They're used with nuts or tapped holes. Several examples are shown below.  Socket Screws: While many hex cap screws may be found in vehicles, socket head screws are becoming more popular and have some space saving advantages over hex cap screws. Socket heads take up less space themselves and don't require side room for wrenches. They also are usually made from stronger alloy steel vs. hex cap screws, but this depends on the grade and manufacturer.  Allen / Hex Socket vs Torx: Most socket head screws accept a hex or Allen wrench (6 sided), but Torx heads (loosely, a 6 pointed star) are also available. Torx sockets were originaly designed to prevent the driver from camming out, and can transfer more torque than a Phillips or slotted driver. They don't require large amounts of pressure to keep the bit in the socket. Some people say that it's faster to insert a bit into a Torx screw than a hex socket, which would be advantageous in manufacturing environments.  Button Head: This head is largely decorative and somewhat similar to a round head, but flatter.  Flat head (counter sunk): These require a pre-drilled counter sink, and are typically angled at 82 degrees (Unified thread), which, by the way, is not the angle created by most drill bits (118 degrees). Metric flat heads have 90 degree angles.  Shoulder Screws: These have precision ground shanks that remain above the head of a hole and provide a simple way to make an axel for a wheel. They are also used when something must be secured, but not clamped.  Set Screws: These are threaded along their entire length and are typically used to secure a shaft from rotating. They're used in pulleys, sprockets, collars and knobs among other things.

Common Head Types for the Above Screws (and 3 machine screws)  Slotted, Phillips and Square drives: The main drawback of slotted heads is that power driven screw drivers easily cam out. Phillips heads address this problem to a certain extent, but these were actually designed to cause the bit to cam out at a certain point to prevent over-tightening. There have been revisions of the original Phillips head, most notably the patented Pozidriv, which does not have rounded internal corners and won't cause the driving bit to pop out. The square or Robertson drive is least likely to cam out and transfers the greatest amount of torque. The wiki Screw page and this one describe some other less commong drives.  Round vs. Pan head: A pan head is successor to the round head, and is slightly flatter with greater thickness near its circumference than the round head. This supplies more surface area for the driving bit to grip over the round head, especially for slotted or flat drivers.  Carriage Bolts: These have a square shank that sinks into and grips wood when a nut is tightened.  Flat and Oval Head: The most common type of head for wood, these heads end up flush or below the surface of the wood when installed. An oval head is similar, except that it has a decorative rounded top that remains above the surface.  Security Heads (tamper proof): These screws have heads that are either impossible to reverse or require a special driver to operate. Some other types include the spanner (two small holes), tri-wing (used on the Wii), and torx or square drives with pins protruding up in the center of the socket. Some even have sacrificial heads that can be broken off after installing the screw. Here and here are several pictures of these screws.  Hex Washer Head and Truss head: These screws have a built in washer to help distribute load to a wider area. A truss head (not shown) is a flatter and wider than a typical round or pan head and serves the same purpose. These are commonly found on license plates.