Threaded Fasteners - Revision history

TheoCamilleri: Added details to nyloc and distorted nut sections.

2023-09-16T03:50:28Z

Added details to nyloc and distorted nut sections.

TheoCamilleri: /* Threaded Insert */

2023-09-16T03:36:05Z

Threaded Insert

RealHumanBean: /* Torque Accuracy */

2021-02-12T20:40:52Z

Torque Accuracy

RealHumanBean: /* Standards */

2021-02-12T20:39:41Z

Standards

RealHumanBean: /* Torque Accuracy */

2021-02-12T20:36:53Z

Torque Accuracy

RealHumanBean: /* Threaded Insert */

2021-02-12T20:33:47Z

Threaded Insert

FsaeIllumina: /* Reduced Loadability */

2021-02-09T19:47:22Z

Reduced Loadability

FsaeIllumina: /* Further Reading */ Added FSAE reference

2021-02-09T19:45:36Z

FsaeIllumina: /* Reduced Loadability */ improved readability

2021-02-09T19:40:24Z

Reduced Loadability: improved readability

FsaeIllumina at 19:38, 9 February 2021

2021-02-09T19:38:41Z

@@ Line 12: / Line 12: @@
 ===NAS===
 NAS Shear bolts are often used in suspension systems because of their tight diameter tolerances, which means less compliance.
 =Screw Types=
@@ Line 50: / Line 49: @@
 |A specialty fastener that allows quick installation and removal of [[Body Panel|body panels]].
 |}
 ===Reduced Loadability===
 Countersunk, button head, and low profile bolts have weaker heads than hex head or socket head bolts, which can cause them to fail at the base of the head instead of the shank, and at lower load then the shank could withstand. The ISO/DIN standards state that the metric bolts will have "reduced loadability" of 80%, and will be labeled with a "0" before the class. ie. Class 08.8, 010.9, or 012.9.
 * '''Countersunk head''': The title of table 3 from ISO 10642:1997(E) states "Minimum ultimate tensile loads (...) 80% of the values specified in ISO 898-1"
 * '''Low Profile Socket Head''': The title of table 3 from DIN 7984 states "Minimum ultimate tensile loads (...) 80% of the values specified in ISO 898-1"
@@ Line 69: / Line 68: @@
 ===Weld Nut / Riv-Nut===
 ==Locknut==
-Locknuts resist loosening. Other methods can be used to resist loosening: [[Washer#Lock washer|lock washers]], [[Safety Wire|safety wire]], [[Locking Adhesive|locking adhesive]], or design. Most locknuts are only designed to be installed a few times otherwise their loosening resistance is diminished.
+Locknuts resist loosening. Other methods can be used to resist loosening: [[Washer#Lock washer|lock washers]], [[Safety Wire|safety wire]], [[Locking Adhesive|locking adhesive]], or design. Most locknuts are only designed to be installed a few times otherwise their loosening resistance is diminished. Locknuts that rely on a prevailing torque, such as nylocs or distorted thread nuts, can effect the torque required to reach a desired bolt preload.
 {| class="wikitable" style="width: 1661px;" data-mce-style="width: 1661px;"
 |-
@@ Line 87: / Line 84: @@
 |-
 | style="width: 39px;" data-mce-style="width: 39px;"|<br />
-| style="width: 106px;" data-mce-style="width: 106px;"|Nylok
+| style="width: 106px;" data-mce-style="width: 106px;"|Nyloc/Nylon Insert Nut<br />
-| style="width: 1476px;" data-mce-style="width: 1476px;"|<br />
+| style="width: 1476px;" data-mce-style="width: 1476px;"|These nuts use a nylon collar to increase friction with the mating thread. As they rely on nylon to provide the prevailing torque, their maximum use temperature is limited to <100-120°C. FSAE/FS rules may prohibit use of nyloc nuts in high temperature locations. Re-use of nyloc nuts depends on the appropriate regulations, but generally they can be re-used, provided the prevailing torque is still sufficient.<br />
 |-
 | style="width: 39px;" data-mce-style="width: 39px;"|<br />
@@ Line 96: / Line 93: @@
 K-nut / Jet-nut
-| style="width: 1476px;" data-mce-style="width: 1476px;"|Different components of the nut can be distorted to prevent loosening. For example: thread pitch and eccentricity. The temperature range is limited only by the parent metal or its plating and can be reused approximately 10 times before its locking capability is diminished<ref>Barrett, Richard. [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900009424.pdf|"Fastener Design Manual"], Nasa Reference Publication 1228 (1990) pp7</ref>. A K-nut or Jet-nut is ideal for high temperature applications.
+| style="width: 1476px;" data-mce-style="width: 1476px;"|Different components of the nut can be distorted to prevent loosening. For example: thread pitch and eccentricity. The temperature range is limited only by the parent metal or its plating and can be reused approximately 10 times before its locking capability is diminished<ref>Barrett, Richard. [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900009424.pdf|"Fastener Design Manual"], Nasa Reference Publication 1228 (1990) pp7</ref>. A K-nut or Jet-nut is ideal for high temperature applications. These types of locknuts may strip coatings/platings off of and wear down the threads of the mating bolt. When the prevailing torque has diminished, the bolt should also be replaced.<br />
 |-
 | style="width: 39px;" data-mce-style="width: 39px;"|
@@ Line 102: / Line 99: @@
 | style="width: 1476px;" data-mce-style="width: 1476px;"|
 |}
 ==Threaded Insert==
@@ Line 108: / Line 106: @@
 Heat-set or heat-stake inserts can be used in parts made from thermoplastics, like FDM 3D prints. These inserts can be installed using a soldering iron, and are often used in plastic parts as a substitute for a tapped hole.
 =Fastener Characteristics (how to choose)=
@@ Line 125: / Line 122: @@
 ==Torque Accuracy==
 The ultimate goal of torque is to tension the bolt. Unfortunately, torque is a very inaccurate method of achieving a specific tension. The tension can be off by +/- 25%.<ref name="NASA"></ref> It widely used because it is cheap to apply. When following a torque spec, be careful to follow the guidelines for assembling, as the use of lubricants such as engine oil can significantly change the measured torque for a given bolt stress (which is what you ultimately care about). NEVER try to guess torque by feel, no matter how experienced you are. A good torque wrench is essential, and torque wrenches that mechanically disengage when a dialed in torque is reached are nice to have.
 ==Calculate Torque==
 The Fastenal Technical reference guide<ref name="Fastenal"> [http://www-eng.lbl.gov/~shuman/NEXT/MATERIALS&COMPONENTS/Pressure_vessels/FastenalTechnicalReferenceGuide.pdf Fastenal Technical Reference Guide]</ref> and the NASA Fastener Design Manual<ref name="NASA">https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900009424.pdf NASA Fastener Design Manual</ref> (Pg 17 Alternative Torque Formula), and Shigley's<ref name="Shigleys">Budynas, Nisbett. Shigley's Mechanical Engineering Design 9th edition</ref> show the commonly used formula:
 Where
 * <math> T </math> is Torque applied to the head of the fastener
@@ Line 139: / Line 135: @@
 =====Locknuts with Torque Calculations=====
 Note that using nylon insert "locknuts" or prevailing torque nuts will increase the torque required for a given bolt tension. This torque is independent of the tension, so you can measure how much additional torque is required to overcome this locking feature, and simply add it on top of the calculation.
 =====The Lazy Way=====
 [https://www.fastenal.com/en/83/torque-calculator Fastenal Torque Calculator]
 * [https://www.youtube.com/watch?v=f7qkHxG1v1E tarkka Fasteners Introduction Youtube Video]
 * [https://www.fsaeonline.com/cdsweb/gen/DownloadDocument.aspx?DocumentID=5eafc7b3-b61d-470c-b929-7ad95d426d97 FSAE Online Series Resources: Threaded Fasteners for FSAE] If link breaks, it is found under fsaeonline.com > Series Resources > Design Event > Reference Documents.

@@ Line 104: / Line 104: @@
 ==Threaded Insert==
-Threaded inserts are used to either repair a damaged set of threads or to make a more robust bolted joint. They are often referred to as "helical inserts" or "helicoils". A thread with a larger size than the bolt thread is tapped into the parent object. The helical insert is then screwed into the tapped hole and locked in place. The inside of the helical insert is the desired thread size. Threaded inserts are most useful for repairs or for parts where repeated assembly is foreseen. Aluminum parts are especially prone to being stripped when torqued, as a FSAE team will likely assemble and disassembled components such as engine casings far more frequently (and roughly!) than the manufacturers predict. Therefore, a set of helical inserts and associated tools are very useful for common fasteners like M6x1.0 screws for engines.
+Threaded inserts are used to either repair a damaged set of threads, to create a stronger bolted joint in relatively weak materials like magnesium & aluminum, or for bolted joints that will be frequently assembled and dis-assembled. Cast aluminum parts are especially prone to being stripped when torqued, as a FSAE team will likely assemble and disassembled components such as engine casings far more frequently (and roughly!) than the manufacturers predict. Therefore, a set of helical thread inserts and associated tools are very useful for common fasteners like M6x1.0 screws for engines. Common types of threaded inserts include Helicoils, Timeserts and Keenserts. Typically, installation of a threaded insert requires a thread with a larger size than the bolt thread in parent object. Different size inserts are available based on the part's wall thickness and the required insert strength (when used to strengthen the bolted joint, larger inserts will result in a stronger joint). The male thread of a thread insert is often an uncommon thread form, and care should be taken to ensure the correct tap is used. The threaded insert is then screwed into the tapped hole and locked in place. The female thread of the threaded insert is the desired thread size.
 =Fastener Characteristics (how to choose)=

@@ Line 121: / Line 121: @@
 ==Torque Accuracy==
-The ultimate goal of torque is to tension the bolt. Unfortunately, torque is a very inaccurate method of achieving a specific tension. The tension can be off by +/- 25%.<ref name="NASA"></ref> It widely used because it is cheap to apply. When following a torque spec, be careful to follow the guidelines for assembling, as the use of lubricants such as engine oil can significantly change the measured torque for a given bolt stress (which is what you ultimately care about). NEVER try to guess torque by feel, no matter how experienced you are. A good torque wrench is essential, and torque wrenches that mechanically disengaging when a dialed in torque is reached are nice to have.
+The ultimate goal of torque is to tension the bolt. Unfortunately, torque is a very inaccurate method of achieving a specific tension. The tension can be off by +/- 25%.<ref name="NASA"></ref> It widely used because it is cheap to apply. When following a torque spec, be careful to follow the guidelines for assembling, as the use of lubricants such as engine oil can significantly change the measured torque for a given bolt stress (which is what you ultimately care about). NEVER try to guess torque by feel, no matter how experienced you are. A good torque wrench is essential, and torque wrenches that mechanically disengage when a dialed in torque is reached are nice to have.
 ==Calculate Torque==

@@ Line 1: / Line 1: @@
 Threaded fasteners used in FS are most typically made of steel but are sometimes also made of stainless, titanium, or aluminum.
 =Standards=
-There are two main threaded fastener standards: metric and inch. Within these two categories lay additional standards set by various organisations. These standards may are often intercompatible but can differ in head size, strength, alloy, coating, pitch, and local avaliability.
+There are two main threaded fastener standards: metric and inch. Within these two categories lay additional standards set by various organisations. These standards may are often intercompatible but can differ in head size, strength, alloy, coating, pitch, and local avaliability. Teams that use both (e.g. a team in the U.S. with metric fasteners for the engine and inch fasteners for the rest of the car) should be extremely careful not to mix up the fasteners as certain metric/inch fasteners can thread with each other and compromise a bolted joint.
 ==Metric==
 Metric screws are listed in the following way:<code><nowiki>M6x25 x 1mm Class 8.8</nowiki></code>. The M6 referes to the major diameter being 6mm, 25: the shaft length is 25mm, and the pitch is 1 thread per 1mm. A class 8.8 bolt is a medium strength steel bolt with a tensile strength of about 800MPa and about 80% of that being the yield strength.
@@ Line 11: / Line 11: @@
 [grades, charts, etc...]
 ===NAS===
 NAS Shear bolts are often used in suspension systems because of their tight diameter tolerances, which means less compliance.
 =Screw Types=

@@ Line 120: / Line 120: @@
 ==Torque Accuracy==
-The ultimate goal of torque is to tension the bolt. Unfortunately, torque is a very inaccurate method of achieving a specific tension. The tension can be off by +/- 25%.<ref name="NASA"></ref> It widely used because it is cheap to apply.
+The ultimate goal of torque is to tension the bolt. Unfortunately, torque is a very inaccurate method of achieving a specific tension. The tension can be off by +/- 25%.<ref name="NASA"></ref> It widely used because it is cheap to apply. When following a torque spec, be careful to follow the guidelines for assembling, as the use of lubricants such as engine oil can significantly change the measured torque for a given bolt stress (which is what you ultimately care about). NEVER try to guess torque by feel, no matter how experienced you are. A good torque wrench is essential, and torque wrenches that mechanically disengaging when a dialed in torque is reached are nice to have.
 ==Calculate Torque==

← Older revision		Revision as of 20:33, 12 February 2021
Line 103:		Line 103:

	==Threaded Insert==		==Threaded Insert==
		+	Threaded inserts are used to either repair a damaged set of threads or to make a more robust bolted joint. They are often referred to as "helical inserts" or "helicoils". A thread with a larger size than the bolt thread is tapped into the parent object. The helical insert is then screwed into the tapped hole and locked in place. The inside of the helical insert is the desired thread size. Threaded inserts are most useful for repairs or for parts where repeated assembly is foreseen. Aluminum parts are especially prone to being stripped when torqued, as a FSAE team will likely assemble and disassembled components such as engine casings far more frequently (and roughly!) than the manufacturers predict. Therefore, a set of helical inserts and associated tools are very useful for common fasteners like M6x1.0 screws for engines.
		+
	=Fastener Characteristics (how to choose)=		=Fastener Characteristics (how to choose)=

← Older revision		Revision as of 19:47, 9 February 2021
Line 61:		Line 61:

	* '''not''' made to a strength standard. These will not have 08.8, 010.9, or 012.9 etc printed on the head.		* '''not''' made to a strength standard. These will not have 08.8, 010.9, or 012.9 etc printed on the head.
		+
		+	Also note that the Formula SAE / Formula Student rules may prevent countersunk, button head, or low profile bolts in certain locations.

	=Nut Types=		=Nut Types=

@@ Line 138: / Line 138: @@
 =Further Reading=
 * [https://www.youtube.com/watch?v=f7qkHxG1v1E tarkka Fasteners Introduction Youtube Video]
 * Machinerys Handbook
 * [http://www-eng.lbl.gov/~shuman/NEXT/MATERIALS&COMPONENTS/Pressure_vessels/FastenalTechnicalReferenceGuide.pdf Fastenal Technical Reference Guide]

@@ Line 52: / Line 52: @@
 Countersunk, button head, and low profile bolts have weaker heads than hex head or socket head bolts, which can cause them to fail at the base of the head instead of the shank, and at lower load then the shank could withstand. The ISO/DIN standards state that the metric bolts will have "reduced loadability" of 80%, and will be labeled with a "0" before the class. ie. Class 08.8, 010.9, or 012.9.
-* '''Countersunk head''': ISO 10642:1997(E) Hexagon Socket Countersunk Head Screws. The title of table 3 states "Minimum ultimate tensile loads (...) 80% of the values specified in ISO 898-1"
+* '''Countersunk head''': The title of table 3 from ISO 10642:1997(E) states "Minimum ultimate tensile loads (...) 80% of the values specified in ISO 898-1"
-* '''Low Profile Socket Head''': DIN 7984. The title of table 3 states "Minimum ultimate tensile loads (...) 80% of the values specified in ISO 898-1"
+* '''Low Profile Socket Head''': The title of table 3 from DIN 7984 states "Minimum ultimate tensile loads (...) 80% of the values specified in ISO 898-1"
-* '''Button Head''': ISO 7380 Hexagon Socket Button Head Screws. The title of table 3 states "Minimum ultimate tensile loads (...) 80% of the values specified in ISO 898-1"
+* '''Button Head''': The title of table 3 from ISO 7380: states "Minimum ultimate tensile loads (...) 80% of the values specified in ISO 898-1"
 =====Caution:=====
@@ Line 60: / Line 60: @@
 * '''not''' made according to one of the aforementioned standards. If they are not advertised as conforming to one of those standards, then their load capability cannot be confirmed (Or look up the standard they are made to).
 * '''not''' made to a strength standard. These will not have 08.8, 010.9, or 012.9 etc printed on the head.
 =Nut Types=