Screws - Revision history

Yash: /* How tight should a screw be?https://www.elexp.com/Images/AllAboutScrews.pdf */

2018-02-21T10:03:10Z

‎How tight should a screw be?https://www.elexp.com/Images/AllAboutScrews.pdf

Yash at 10:02, 21 February 2018

2018-02-21T10:02:38Z

Yash: /* How tight should a screw be? */

2018-02-21T10:02:16Z

‎How tight should a screw be?

Yash: /* Selection criteria of the screw for satellite */

2018-02-21T09:46:10Z

‎Selection criteria of the screw for satellite

Yash: /* Screws v/s Bolts */

2018-02-21T09:43:28Z

‎Screws v/s Bolts

Yash: /* Screw Drives */

2018-02-21T09:41:48Z

‎Screw Drives

Yash: /* Screws v/s Bolts */

2018-02-21T09:29:45Z

‎Screws v/s Bolts

Yash: /* Introduction */

2018-02-21T09:27:35Z

‎Introduction

Yash: /* Screw Heads */

2018-02-20T22:34:28Z

‎Screw Heads

Yash: /* Screw Heads */

2018-02-20T22:32:37Z

‎Screw Heads

@@ Line 67: / Line 67: @@
 Additional tightening preload does not buy any additional fatigue protection as long as joint separation does not happen.
-=== How to achieve the required tightness? <ref name = "allabout" />===
+=== How to achieve the required tightness? ===
 According to the Machinery's handbook, tightening by feel is only +-35% accurate. Using a torque wrench improves the accuracy to only about +-25%. These uncertainties are huge, and thus, we should not to tighten too close to yield, or too loose.  They give a good reason to design a joint so that it will still work with a wide range of possible pre-loads. There's a method called "turn-of-nut" which can supposedly get within +-10% accuracy, but it relies heavily on a reliable starting point from which to start counting turns. (see Machinery's handbook).

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 See https://www.boltdepot.com/fastener-information/materials-and-grades/bolt-grade-chart.aspx for more information on these marking schemes.
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 If you are done reading this page, you can go back to [[Mechanical Subsystem]]

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 Allen/hex head fasteners are very common in most equipment. These are more durable and less likely to slip. This also allows use of torque wrenches. Hence, allen headed screws are a good alternatives.
-== How tight should a screw be? ==
+== How tight should a screw be?<ref name = "allabout">https://www.elexp.com/Images/AllAboutScrews.pdf</ref> ==
 The tighter the screw, the more friction there is to resist loosening. <br \>
-Screws are very likely to come loose if any relative motion occurs between the threads. Static friction is substantially higher than sliding friction, so once movement in one direction starts, it becomes much easier for unscrewing motion to happen. <br \>
+Screws are quite likely to come loose if relative motion takes place between the threads. Static friction is very much higher than sliding friction, so once movement in a direction is onset, it becomes much easier for unscrewing motion to happen. <br \>
-As a follow up, bolts are less resistant to shear (sideways) loads, so more clamping force and friction helps reduce these loads. <br \>
+Bolts are less resistant to shear loads, so higher clamping force and friction should be used to reduce these loads. <br \>
-As long as joint separation does not occur, additional tightening preload does not buy any additional fatigue protection.
+Additional tightening preload does not buy any additional fatigue protection as long as joint separation does not happen.
-=== How to achieve the required tightness? ===
+=== How to achieve the required tightness? <ref name = "allabout" />===
-According to the Machinery's handbook, tightening by feel is only +-35% accurate, and using a torque wrench only improves the accuracy to about +-25%. These uncertainties are massive, and give good reason not to tighten too close to yield, or too loose, and also to design a joint so that it will still work with a huge span of possible pre-loads. A method called "turn-of-nut" can supposedly get within +-10%, but this relies heavily on a reliable starting point from which to start counting turns (see Machinery's handbook).
+According to the Machinery's handbook, tightening by feel is only +-35% accurate. Using a torque wrench improves the accuracy to only about +-25%. These uncertainties are huge, and thus, we should not to tighten too close to yield, or too loose.  They give a good reason to design a joint so that it will still work with a wide range of possible pre-loads. There's a method called "turn-of-nut" which can supposedly get within +-10% accuracy, but it relies heavily on a reliable starting point from which to start counting turns. (see Machinery's handbook).
 ----
@@ Line 75: / Line 75: @@
 '''Metric ISO Marking''' <br \>
-Metric fasteners are marked with two numbers separated by a decimal point, like 10.9. The 10 is 1/100th of tensile strength in MPa, and the .9 represents the ratio of yield to tensile strength. So 10.9 represents a tensile strength of 1000 MPa and yield of 900 MPa.
+Metric fasteners are marked with two numbers separated by a decimal point, like 10.9. The 10 is 1/100th of tensile strength in MPa, and the .9 represents the ratio of yield to tensile strength. So 10.9 represents a tensile strength of 1000 MPa and yield of 900 MPa. <br \><br \>
 == References ==

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 == Selection criteria of the screw for satellite ==
 Screws are used to attach any two surfaces in contact on our satellite. The size of the screw will be decided by the maximum depth of penetration of the hole. The screws are generally made of the material SS304 (stainless steel). <br \>
-Single slotted and Phillip screws tend to slip off while using a screwdriver to screw them.These fasteners are easily damaged at the slot. In addition, these are hard to use with a torque wrench. <br \>
+Single slotted and Phillips screws tend to slip off while using a screwdriver to screw them.These fasteners are easily damaged at the slot. In addition, these are hard to use with a torque wrench. <br \>
 Allen/hex head fasteners are very common in most equipment. These are more durable and less likely to slip. This also allows use of torque wrenches. Hence, allen headed screws are a good alternatives.

@@ Line 9: / Line 9: @@
 Both screws and bolts are externally threaded fasteners. <br \>
 A bolt is designed for insertion through holes in assembled parts. It is normally intended to be tightened or released by torquing a nut.  <br \>
-A screw is capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread. It can be tightened or released by torquing the head. A nut is not required. <ref>A bolt is an externally threaded fastener designed for insertion through holes in assembled parts, and is normally intended to be tightened or released by torquing a nut.
+A screw is capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread. It can be tightened or released by torquing the head. A nut is not required. <ref>http://www.threadall.com/bolts </ref> <br \>
 [[File:Screw3.jpg|thumb|left|300px|Screw. Image reproduced from [https://commons.wikimedia.org/wiki/File:Phillips_screw.jpg here]]]
 [[File:Bolt2.jpg|thumb|center|300px|Bolt. Image reproduced from [https://commons.wikimedia.org/wiki/File:Bolt_nut.jpg here]]]

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 Visit https://en.wikipedia.org/wiki/Screw#Screw_head_shapes for a comprehensive treatment of this topic.
-== Screw Drives ==
+== Screw Drives <ref>http://www.fastenersuperstore.com/fastener-guides/screws-drive-styles</ref>==
 A screw drive is a pattern which is used to turn a screw. It allows torque to be applied to it usually by using a mating tool, such as a screwdriver, that is used to turn it. <br \>
 ==== Phillips drive ====
-Phillips drives are the most common type of screw drive. They were developed as one of the first alternatives to the slotted drive.
+Phillips drives are among the most common type of screw drives.
 [[File:Phillips2.jpg|frame|center|Image reproduced from [https://commons.wikimedia.org/wiki/File:Screwhead_Anaglyph.jpg here]]]
 ==== Slotted Drive ====
-The slotted drive is the oldest drive still commonly used today. They provide less torque than other drives and are subject to slippage.
+The slotted drive, though the oldest drive, is still commonly used today. They are subject to slippage and provide lesser torques than other drives.
 [[File:Slotted2.png|thumb|center|200px|Image reproduced from [https://commons.wikimedia.org/wiki/File:Screw_Head_-_Slotted.svg here]]]
 ==== Socket Drive ====
-Socket drive screws contain a hex shaped internal socket which is tightened or loosened using a hex key or allen wrench.
+These drives have a hex shaped internal socket. A hex key or allen wrench is used to tighten or loosen it.
 [[File:Socket2.png|thumb|center|200px|Image reproduced from [https://commons.wikimedia.org/wiki/File:Screw_Head_-_Hex_Socket.svg here]]]
 ==== Hex Drive ====
-One of the few drives turned by using the outside of the head rather than the inside. Hex head screws are installed with a socket, usually connected to a ratcheting tool or a power driver.
+This one is interesting. It is one of the few drives which is turned the outside of the head rather than the inside. Hex head screws are installed with a socket, usually connected to a ratcheting tool or a power driver.
 [[File:Hex2.png|thumb|center|200px|Image reproduced from [https://pixabay.com/en/nut-bolt-black-silhouette-hexagon-309717/ here]]]
 ==== Robertson Drive ====
-Square drives have a square shaped socket which has a slight taper as it goes deeper into the screw head. The four 90° angles provide strong torque and decrease the possibility of slippage.
+These have a square shaped socket which tapers slightly with depth into the screw head. Strong torque is provided by the four 90° angles. They decrease the possibility of slippage.
 [[File:Square2.png|thumb|center|200px|Image reproduced from [https://commons.wikimedia.org/wiki/File:Screw_f.svg here]]]
 ==== U Drive ====
-A U drive screw is also known as a hammer drive screw. It is set in a properly sized pilot hole and then driven into place with a hammer. The threads of the screw turn as it is driven, creating the fastening action.
+Also known as a hammer drive screw, it is set in a properly sized pilot hole. It is then driven into place with a hammer. Quite interestingly, the threads of this screw turn as it is driven, thereby creating the fastening action.
 [[File:UDrive2.jpg|thumb|center|200px|Image reproduced from [http://maxpixel.freegreatpicture.com/Nail-Fixing-Hammer-Hammering-Metal-157381 here]]]

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 == Introduction ==
 Well we all know what screws are, but nevertheless we’ll provide you with the bookish definition. <br \>
-''A short, slender, sharp-pointed metal pin with a raised helical thread running around it and a slotted head, used to join things together.'' <br \>
+''A short, slender, sharp-pointed metal pin with a raised helical thread running around it and a slotted head, used to join things together.'' <ref>https://en.oxforddictionaries.com/definition/screw</ref> <br \>
-The cylindrical portion of the screw from the underside of the head to the tip is known as the shank; it may be fully threaded or partially threaded. The distance between each thread is called the pitch. <br \>
+As can be seen in the image below, the cylindrical portion of the screw from the underside of the head to the tip is known as the shank. The shank may be fully threaded or partially threaded. Pitch is the distance between each thread. <ref>https://books.google.co.in/books?isbn=1317938100</ref><br \>
-The majority of screws are tightened by clockwise rotation, which is termed a right-hand thread; a common mnemonic device for remembering this when working with screws or bolts is '''righty-tighty, lefty-loosey'''.
+The majority of screws have a right handed thread, meaning that they are tightened by clockwise rotation. A very good mnemonic device for remembering this when working with screws or bolts is '''righty-tighty, lefty-loosey'''. <ref>http://www.solidswiki.com/index.php?title=Screws&mobileaction=toggle_view_mobile</ref>
 [[File:Screw Nomen.png|thumb|center|600px|Screw Nomenclature. Image reproduced from [https://pixabay.com/en/bolt-nut-screw-2024571/ here]]]

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 == Screw Heads ==
 [[File:ScrewHeads.png|frame|center| (a) pan, (b) dome (button), (c) round, (d) truss (mushroom), (e) flat (countersunk), (f) oval (raised head). Attribution: CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2452317]]
 == Screw Drives ==