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Selecting An Appropriate Bolt
On Wednesday, April 19, 2017 at 8:56:36 PM UTC-7, wrote:
On Thu, 20 Apr 2017 09:52:15 +0700, John B Slocomb wrote: On Wed, 19 Apr 2017 18:23:53 -0400, wrote: On Wed, 19 Apr 2017 18:43:02 +0700, John B Slocomb wrote: Metric thread pitch is described totally different than inch size bolts. Inch size is threads per inch. Metric thread is thread pitch - so in inch size bolts, a higher number is a finer thread - in metric a higher number is a coarser thread. A 6X10 metric bolt is 6mm with a thread pitch of 1mm crest to crest (or root to root - however you want to measure it) Who cares, along as the people involved know what you are talking about? Ant metering system is just that, a system which works for those that use it. The old method of measuring gear ratios on a bicycle was to use "gear inches" which described the diameter of a wheel that would move the distance in one revolution. Rather archaic today but made perfect sense to those that used it. As far as the "grade" of the bolt - a "grade 8" is NOT always better than a "grade 5" or even, possibly, in some cases, a "grade 2" A grade 2 or grade 5 bolt may bend and stretch - and still hold, where a grade 8 would simply snap. It depends on what kind of load is being carried by the bolt - and how it is torqued. On the same vein, a bolt that is undertorqued CAN fail faster than one that is overtorqued. A properly tensioned bolt is "pre-stretched" just enough that any cyclic load does not stretch the bolt any farther, so the bolt does not fatigue in use. An exciting theory and technically correct. although I would comment that I've yet to see an under torque bolt break. It's far from "theory" - I've seen numerous head bolts and manifold bolts fail that were attributed to being under-torqued on vehicles that were not properly PDId, and quite a few bolts that failed in shear because they were not properly tightened, and/or the holes were not properly de-burred, allowing the bolt to loose tension. No use arguing with Slocumb though - you'll never get anything through his thick skull. You must have a tremendous amount of experience with nuts and bolts. As I mentioned I've been fooling with them things for about 70 years now and frankly I've never seen "numerous" head bolts fail. Yes, I've seen head bolts fail, but I would use the term "rarely" not "Numerous". I would have to say that if you have seen numerous head bolts fail then you are associating with some very incompetent mechanics. And how does one determine that they were under torqued after they have failed? Notb incompetent mechanics - but poor factory assembly. Don't take my word for the FACT the problem exists. See: http://www.croberts.com/bolt.htm In particular Picture #10. As for broken head bolts - see: https://www.bimmerforums.com/forum/s...ken-Head-Bolts Also see: http://www.boltscience.com/pages/Failure%20Modes.swf and: https://www.hiretorque.co.uk/failure...bolted-joints/ -Particularly item #3 3. Fatigue Failures Fatigue failures typically occur within a couple of threads, where the bolt engages into the internal thread. Failure is then reached due to the high stress gradient within the region. Fatigue failures can be particularly hazardous because they often occur with no visible warning signs and the failure is often sudden. Fatigue failures are often unknowingly avoided in gasketed joints simply because the required crush for the gasket often dictates a torque or bolt tension that minimizes the risk of a fatigue failure. However, changing to a new gasket type later on which requires less crush may be the initial cause of bolt fatigue failure. It is not unusual to assume that a bolt has failed due to overload when it has in fact failed from fatigue, which can also be a consequence of self-loosening. Also: http://www.bluetoad.com/article/Bolt...0/article.html and: http://www.onallcylinders.com/2014/0...ener-failures/ Also: https://www.excelcalcs.com/engineeri...-joints-fail?/ The first cause listed: Insufficient Clamp force? - Usually by applying a measured torque load to the nut bolted joints are tightened to achieve a specific clamp load. Even under the most extreme applied loads, the clamping force must prevent joint movement between clamped parts. Movement includes both opening of the joint to form gaps and slipping. Loads applied to the joint may be axial forces (in the direction of the bolt axis) and/or shear forces (perpendicular to the bolt axis). If slippage occurs then the joint may fail by the bolt loosening. If a gap in the joint opens then a bolt failure by fatigue is more likely to occur. Typically bolt fatigue failures occur because of insufficient preload rather than poor fatigue strength of the bolt. Improving the method of tightening can reduce the scatter in bolt preload and help guarantee the minimum required clamping force Pay particular attention to the sectionfollowing the "bolted joint.xls" link which explains things in pretty plain language. You may have worked on machines, including aircraft without fully understanding what you were doing or why. I have not only worked on cars and agricultural equipment and industrial equipment (loaders and dozers etc) and been rather extensively involved with amateur built/homebuilt/experimental aviation, I have also taught automotive mechanics at the secondary school AND post secondary (trade) level. That Figure 10 was not a "failure" per se. The bolt did not break from under tightening - it wore the threads off. Eventually indeed it would have broken. Head bolts on cars can be said to ALWAYS break from over-torquing. What occurs is that you over-torque the head bolts and then when the engine heats up and expands it blows the top of the bolt off from exceeding the mechanical strength of the bolt. Sometimes you can hear it go. I rarely use a torque wrench because you can FEEL the torque that should be applied and using a torque wrench a number of times shows you that it almost always feels under-torqued. So you develope a feel for it. A correctly designed piece is supposed to use the mechanical strength of a large number of bolts and not the near maximum strength of a few. This is the mistake that is almost always made on that great "German engineering". They use calculations instead of common sense. Ten headbolts torqued within 10% of the proper torque are better than 6 headbolts designed to carry the load if properly torqued to exactly the correct value. Which reminds me of what is becoming with the carbon fiber engineering these days. It isn't "great engineering" to make a 12 lb bike that can kill it's rider with a single manufacturing flaw. |
Selecting An Appropriate Bolt
On Thu, 20 Apr 2017 16:17:14 +0700, John B Slocomb
wrote: On Wed, 19 Apr 2017 23:56:34 -0400, wrote: On Thu, 20 Apr 2017 09:52:15 +0700, John B Slocomb wrote: On Wed, 19 Apr 2017 18:23:53 -0400, wrote: On Wed, 19 Apr 2017 18:43:02 +0700, John B Slocomb wrote: Metric thread pitch is described totally different than inch size bolts. Inch size is threads per inch. Metric thread is thread pitch - so in inch size bolts, a higher number is a finer thread - in metric a higher number is a coarser thread. A 6X10 metric bolt is 6mm with a thread pitch of 1mm crest to crest (or root to root - however you want to measure it) Who cares, along as the people involved know what you are talking about? Ant metering system is just that, a system which works for those that use it. The old method of measuring gear ratios on a bicycle was to use "gear inches" which described the diameter of a wheel that would move the distance in one revolution. Rather archaic today but made perfect sense to those that used it. As far as the "grade" of the bolt - a "grade 8" is NOT always better than a "grade 5" or even, possibly, in some cases, a "grade 2" A grade 2 or grade 5 bolt may bend and stretch - and still hold, where a grade 8 would simply snap. It depends on what kind of load is being carried by the bolt - and how it is torqued. On the same vein, a bolt that is undertorqued CAN fail faster than one that is overtorqued. A properly tensioned bolt is "pre-stretched" just enough that any cyclic load does not stretch the bolt any farther, so the bolt does not fatigue in use. An exciting theory and technically correct. although I would comment that I've yet to see an under torque bolt break. It's far from "theory" - I've seen numerous head bolts and manifold bolts fail that were attributed to being under-torqued on vehicles that were not properly PDId, and quite a few bolts that failed in shear because they were not properly tightened, and/or the holes were not properly de-burred, allowing the bolt to loose tension. No use arguing with Slocumb though - you'll never get anything through his thick skull. You must have a tremendous amount of experience with nuts and bolts. As I mentioned I've been fooling with them things for about 70 years now and frankly I've never seen "numerous" head bolts fail. Yes, I've seen head bolts fail, but I would use the term "rarely" not "Numerous". I would have to say that if you have seen numerous head bolts fail then you are associating with some very incompetent mechanics. And how does one determine that they were under torqued after they have failed? Notb incompetent mechanics - but poor factory assembly. Don't take my word for the FACT the problem exists. See: http://www.croberts.com/bolt.htm In particular Picture #10. As for broken head bolts - see: https://www.bimmerforums.com/forum/s...ken-Head-Bolts Also see: http://www.boltscience.com/pages/Failure%20Modes.swf and: https://www.hiretorque.co.uk/failure...bolted-joints/ -Particularly item #3 3. Fatigue Failures Fatigue failures typically occur within a couple of threads, where the bolt engages into the internal thread. Failure is then reached due to the high stress gradient within the region. Fatigue failures can be particularly hazardous because they often occur with no visible warning signs and the failure is often sudden. Fatigue failures are often unknowingly avoided in gasketed joints simply because the required crush for the gasket often dictates a torque or bolt tension that minimizes the risk of a fatigue failure. However, changing to a new gasket type later on which requires less crush may be the initial cause of bolt fatigue failure. It is not unusual to assume that a bolt has failed due to overload when it has in fact failed from fatigue, which can also be a consequence of self-loosening. Also: http://www.bluetoad.com/article/Bolt...0/article.html and: http://www.onallcylinders.com/2014/0...ener-failures/ Also: https://www.excelcalcs.com/engineeri...-joints-fail?/ The first cause listed: Insufficient Clamp force? - Usually by applying a measured torque load to the nut bolted joints are tightened to achieve a specific clamp load. Even under the most extreme applied loads, the clamping force must prevent joint movement between clamped parts. Movement includes both opening of the joint to form gaps and slipping. Loads applied to the joint may be axial forces (in the direction of the bolt axis) and/or shear forces (perpendicular to the bolt axis). If slippage occurs then the joint may fail by the bolt loosening. If a gap in the joint opens then a bolt failure by fatigue is more likely to occur. Typically bolt fatigue failures occur because of insufficient preload rather than poor fatigue strength of the bolt. Improving the method of tightening can reduce the scatter in bolt preload and help guarantee the minimum required clamping force Pay particular attention to the sectionfollowing the "bolted joint.xls" link which explains things in pretty plain language. You may have worked on machines, including aircraft without fully understanding what you were doing or why. You are probably right although the A.F. thought I was competent. Or I guess that they did as they kept promoting me and they had me managing divisions for them. Shoot, they even had me writing the skill level tests for my career field one time.Then when I retired from that job I hired on as a mechanic again and ended up some years later being promoted to "Operations Manager" for a fair to middling sized company in Indonesia. Peter principal at work? It was all "Government work" I have not only worked on cars and agricultural equipment and industrial equipment (loaders and dozers etc) and been rather extensively involved with amateur built/homebuilt/experimental aviation, I have also taught automotive mechanics at the secondary school AND post secondary (trade) level. |
Selecting An Appropriate Bolt
On Thu, 20 Apr 2017 07:03:57 -0700 (PDT), wrote:
On Wednesday, April 19, 2017 at 8:56:36 PM UTC-7, wrote: On Thu, 20 Apr 2017 09:52:15 +0700, John B Slocomb wrote: On Wed, 19 Apr 2017 18:23:53 -0400, wrote: On Wed, 19 Apr 2017 18:43:02 +0700, John B Slocomb wrote: Metric thread pitch is described totally different than inch size bolts. Inch size is threads per inch. Metric thread is thread pitch - so in inch size bolts, a higher number is a finer thread - in metric a higher number is a coarser thread. A 6X10 metric bolt is 6mm with a thread pitch of 1mm crest to crest (or root to root - however you want to measure it) Who cares, along as the people involved know what you are talking about? Ant metering system is just that, a system which works for those that use it. The old method of measuring gear ratios on a bicycle was to use "gear inches" which described the diameter of a wheel that would move the distance in one revolution. Rather archaic today but made perfect sense to those that used it. As far as the "grade" of the bolt - a "grade 8" is NOT always better than a "grade 5" or even, possibly, in some cases, a "grade 2" A grade 2 or grade 5 bolt may bend and stretch - and still hold, where a grade 8 would simply snap. It depends on what kind of load is being carried by the bolt - and how it is torqued. On the same vein, a bolt that is undertorqued CAN fail faster than one that is overtorqued. A properly tensioned bolt is "pre-stretched" just enough that any cyclic load does not stretch the bolt any farther, so the bolt does not fatigue in use. An exciting theory and technically correct. although I would comment that I've yet to see an under torque bolt break. It's far from "theory" - I've seen numerous head bolts and manifold bolts fail that were attributed to being under-torqued on vehicles that were not properly PDId, and quite a few bolts that failed in shear because they were not properly tightened, and/or the holes were not properly de-burred, allowing the bolt to loose tension. No use arguing with Slocumb though - you'll never get anything through his thick skull. You must have a tremendous amount of experience with nuts and bolts. As I mentioned I've been fooling with them things for about 70 years now and frankly I've never seen "numerous" head bolts fail. Yes, I've seen head bolts fail, but I would use the term "rarely" not "Numerous". I would have to say that if you have seen numerous head bolts fail then you are associating with some very incompetent mechanics. And how does one determine that they were under torqued after they have failed? Notb incompetent mechanics - but poor factory assembly. Don't take my word for the FACT the problem exists. See: http://www.croberts.com/bolt.htm In particular Picture #10. As for broken head bolts - see: https://www.bimmerforums.com/forum/s...ken-Head-Bolts Also see: http://www.boltscience.com/pages/Failure%20Modes.swf and: https://www.hiretorque.co.uk/failure...bolted-joints/ -Particularly item #3 3. Fatigue Failures Fatigue failures typically occur within a couple of threads, where the bolt engages into the internal thread. Failure is then reached due to the high stress gradient within the region. Fatigue failures can be particularly hazardous because they often occur with no visible warning signs and the failure is often sudden. Fatigue failures are often unknowingly avoided in gasketed joints simply because the required crush for the gasket often dictates a torque or bolt tension that minimizes the risk of a fatigue failure. However, changing to a new gasket type later on which requires less crush may be the initial cause of bolt fatigue failure. It is not unusual to assume that a bolt has failed due to overload when it has in fact failed from fatigue, which can also be a consequence of self-loosening. Also: http://www.bluetoad.com/article/Bolt...0/article.html and: http://www.onallcylinders.com/2014/0...ener-failures/ Also: https://www.excelcalcs.com/engineeri...-joints-fail?/ The first cause listed: Insufficient Clamp force? - Usually by applying a measured torque load to the nut bolted joints are tightened to achieve a specific clamp load. Even under the most extreme applied loads, the clamping force must prevent joint movement between clamped parts. Movement includes both opening of the joint to form gaps and slipping. Loads applied to the joint may be axial forces (in the direction of the bolt axis) and/or shear forces (perpendicular to the bolt axis). If slippage occurs then the joint may fail by the bolt loosening. If a gap in the joint opens then a bolt failure by fatigue is more likely to occur. Typically bolt fatigue failures occur because of insufficient preload rather than poor fatigue strength of the bolt. Improving the method of tightening can reduce the scatter in bolt preload and help guarantee the minimum required clamping force Pay particular attention to the sectionfollowing the "bolted joint.xls" link which explains things in pretty plain language. You may have worked on machines, including aircraft without fully understanding what you were doing or why. I have not only worked on cars and agricultural equipment and industrial equipment (loaders and dozers etc) and been rather extensively involved with amateur built/homebuilt/experimental aviation, I have also taught automotive mechanics at the secondary school AND post secondary (trade) level. That Figure 10 was not a "failure" per se. The bolt did not break from under tightening - it wore the threads off. Eventually indeed it would have broken. Head bolts on cars can be said to ALWAYS break from over-torquing. What occurs is that you over-torque the head bolts and then when the engine heats up and expands it blows the top of the bolt off from exceeding the mechanical strength of the bolt. Sometimes you can hear it go. No, more head bolts fail from undertorque than overtorque. a properly preloADED BOLT WILL not SUFFER A FATIGUE FAILURE, WHILE AN UNDERTORQUED BOLT will EVENTUALLY FAIL DUE TO FATIGUE. iT MIGHT NOT HAPPEN IN THE NORMAL LIFESPAN OF THE ENGINE - BUT IT will HAPPEN UNLESS IT IS GROSSLY OVER-SPEC'D I rarely use a torque wrench because you can FEEL the torque that should be applied and using a torque wrench a number of times shows you that it almost always feels under-torqued. So you develope a feel for it. A correctly designed piece is supposed to use the mechanical strength of a large number of bolts and not the near maximum strength of a few. This is the mistake that is almost always made on that great "German engineering". They use calculations instead of common sense. Ten headbolts torqued within 10% of the proper torque are better than 6 headbolts designed to carry the load if properly torqued to exactly the correct value. Which reminds me of what is becoming with the carbon fiber engineering these days. It isn't "great engineering" to make a 12 lb bike that can kill it's rider with a single manufacturing flaw. |
Selecting An Appropriate Bolt
On Thu, 20 Apr 2017 10:23:50 -0500, AMuzi wrote:
On 4/20/2017 9:03 AM, wrote: On Wednesday, April 19, 2017 at 8:56:36 PM UTC-7, wrote: On Thu, 20 Apr 2017 09:52:15 +0700, John B Slocomb wrote: On Wed, 19 Apr 2017 18:23:53 -0400, wrote: On Wed, 19 Apr 2017 18:43:02 +0700, John B Slocomb wrote: Metric thread pitch is described totally different than inch size bolts. Inch size is threads per inch. Metric thread is thread pitch - so in inch size bolts, a higher number is a finer thread - in metric a higher number is a coarser thread. A 6X10 metric bolt is 6mm with a thread pitch of 1mm crest to crest (or root to root - however you want to measure it) Who cares, along as the people involved know what you are talking about? Ant metering system is just that, a system which works for those that use it. The old method of measuring gear ratios on a bicycle was to use "gear inches" which described the diameter of a wheel that would move the distance in one revolution. Rather archaic today but made perfect sense to those that used it. As far as the "grade" of the bolt - a "grade 8" is NOT always better than a "grade 5" or even, possibly, in some cases, a "grade 2" A grade 2 or grade 5 bolt may bend and stretch - and still hold, where a grade 8 would simply snap. It depends on what kind of load is being carried by the bolt - and how it is torqued. On the same vein, a bolt that is undertorqued CAN fail faster than one that is overtorqued. A properly tensioned bolt is "pre-stretched" just enough that any cyclic load does not stretch the bolt any farther, so the bolt does not fatigue in use. An exciting theory and technically correct. although I would comment that I've yet to see an under torque bolt break. It's far from "theory" - I've seen numerous head bolts and manifold bolts fail that were attributed to being under-torqued on vehicles that were not properly PDId, and quite a few bolts that failed in shear because they were not properly tightened, and/or the holes were not properly de-burred, allowing the bolt to loose tension. No use arguing with Slocumb though - you'll never get anything through his thick skull. You must have a tremendous amount of experience with nuts and bolts. As I mentioned I've been fooling with them things for about 70 years now and frankly I've never seen "numerous" head bolts fail. Yes, I've seen head bolts fail, but I would use the term "rarely" not "Numerous". I would have to say that if you have seen numerous head bolts fail then you are associating with some very incompetent mechanics. And how does one determine that they were under torqued after they have failed? Notb incompetent mechanics - but poor factory assembly. Don't take my word for the FACT the problem exists. See: http://www.croberts.com/bolt.htm In particular Picture #10. As for broken head bolts - see: https://www.bimmerforums.com/forum/s...ken-Head-Bolts Also see: http://www.boltscience.com/pages/Failure%20Modes.swf and: https://www.hiretorque.co.uk/failure...bolted-joints/ -Particularly item #3 3. Fatigue Failures Fatigue failures typically occur within a couple of threads, where the bolt engages into the internal thread. Failure is then reached due to the high stress gradient within the region. Fatigue failures can be particularly hazardous because they often occur with no visible warning signs and the failure is often sudden. Fatigue failures are often unknowingly avoided in gasketed joints simply because the required crush for the gasket often dictates a torque or bolt tension that minimizes the risk of a fatigue failure. However, changing to a new gasket type later on which requires less crush may be the initial cause of bolt fatigue failure. It is not unusual to assume that a bolt has failed due to overload when it has in fact failed from fatigue, which can also be a consequence of self-loosening. Also: http://www.bluetoad.com/article/Bolt...0/article.html and: http://www.onallcylinders.com/2014/0...ener-failures/ Also: https://www.excelcalcs.com/engineeri...-joints-fail?/ The first cause listed: Insufficient Clamp force? - Usually by applying a measured torque load to the nut bolted joints are tightened to achieve a specific clamp load. Even under the most extreme applied loads, the clamping force must prevent joint movement between clamped parts. Movement includes both opening of the joint to form gaps and slipping. Loads applied to the joint may be axial forces (in the direction of the bolt axis) and/or shear forces (perpendicular to the bolt axis). If slippage occurs then the joint may fail by the bolt loosening. If a gap in the joint opens then a bolt failure by fatigue is more likely to occur. Typically bolt fatigue failures occur because of insufficient preload rather than poor fatigue strength of the bolt. Improving the method of tightening can reduce the scatter in bolt preload and help guarantee the minimum required clamping force Pay particular attention to the sectionfollowing the "bolted joint.xls" link which explains things in pretty plain language. You may have worked on machines, including aircraft without fully understanding what you were doing or why. I have not only worked on cars and agricultural equipment and industrial equipment (loaders and dozers etc) and been rather extensively involved with amateur built/homebuilt/experimental aviation, I have also taught automotive mechanics at the secondary school AND post secondary (trade) level. That Figure 10 was not a "failure" per se. The bolt did not break from under tightening - it wore the threads off. Eventually indeed it would have broken. Head bolts on cars can be said to ALWAYS break from over-torquing. What occurs is that you over-torque the head bolts and then when the engine heats up and expands it blows the top of the bolt off from exceeding the mechanical strength of the bolt. Sometimes you can hear it go. I rarely use a torque wrench because you can FEEL the torque that should be applied and using a torque wrench a number of times shows you that it almost always feels under-torqued. So you develope a feel for it. A correctly designed piece is supposed to use the mechanical strength of a large number of bolts and not the near maximum strength of a few. This is the mistake that is almost always made on that great "German engineering". They use calculations instead of common sense. Ten headbolts torqued within 10% of the proper torque are better than 6 headbolts designed to carry the load if properly torqued to exactly the correct value. Which reminds me of what is becoming with the carbon fiber engineering these days. It isn't "great engineering" to make a 12 lb bike that can kill it's rider with a single manufacturing flaw. There are cases where an experienced mechanic can torque properly to within the correct range without a torque wrench. Unfortunately, there are also times when you thought you did, but you didn't. On some parts, the result of such negligence isn't critical, unlike airplanes. After a few "near misses" at the dealership I started spot checking wheel torques on vehicles that had wheels removed for service - any wheel that had been installed with an impact and not checked with a torque wrench was possible grounds for dismissal. I also spot checked head torque on new vehicles after PDI.We were paid to check them. If not checked there washell to pay! |
Selecting An Appropriate Bolt
On Thursday, April 20, 2017 at 1:37:18 AM UTC-4, Art Shapiro wrote:
On 4/17/2017 1:52 PM, Doug Landau wrote: Get a new stem. This one is a flawed design. There is built-in problem with the shape of the part, and that is a lack of remaining metal around the bolt hole. The stem has been made bigger around the front bolt hole to overcome this, but it still has the 2-bolt-1-failure problem. The traditional shape does not make this concession to ease-of-handlebar-change, and carefully places the single bolt in the rear where there is plenty of metal surrounding the threads. The traditional design is both less likely to experience a bolt failure, and - in the wild guess dept., be more likely to hold on to the bars and remain usable in the event that one does. I'm he OP. It so happens that the rear bolt was the one that snapped, which seems to contradict your assertion about the design's weak point. Art With all ofthe replies about just about everything else, did you get a definitive reply that ANSWERED your question about whether to use a Grade 5 or Grade 8 bolt? If it were me i'd use the strongest grade I could get. Cheers |
Selecting An Appropriate Bolt
On 4/19/2017 11:56 PM, wrote:
On Thu, 20 Apr 2017 09:52:15 +0700, John B Slocomb wrote: On Wed, 19 Apr 2017 18:23:53 -0400, wrote: On Wed, 19 Apr 2017 18:43:02 +0700, John B Slocomb wrote: Metric thread pitch is described totally different than inch size bolts. Inch size is threads per inch. Metric thread is thread pitch - so in inch size bolts, a higher number is a finer thread - in metric a higher number is a coarser thread. A 6X10 metric bolt is 6mm with a thread pitch of 1mm crest to crest (or root to root - however you want to measure it) Who cares, along as the people involved know what you are talking about? Ant metering system is just that, a system which works for those that use it. The old method of measuring gear ratios on a bicycle was to use "gear inches" which described the diameter of a wheel that would move the distance in one revolution. Rather archaic today but made perfect sense to those that used it. As far as the "grade" of the bolt - a "grade 8" is NOT always better than a "grade 5" or even, possibly, in some cases, a "grade 2" A grade 2 or grade 5 bolt may bend and stretch - and still hold, where a grade 8 would simply snap. It depends on what kind of load is being carried by the bolt - and how it is torqued. On the same vein, a bolt that is undertorqued CAN fail faster than one that is overtorqued. A properly tensioned bolt is "pre-stretched" just enough that any cyclic load does not stretch the bolt any farther, so the bolt does not fatigue in use. An exciting theory and technically correct. although I would comment that I've yet to see an under torque bolt break. It's far from "theory" - I've seen numerous head bolts and manifold bolts fail that were attributed to being under-torqued on vehicles that were not properly PDId, and quite a few bolts that failed in shear because they were not properly tightened, and/or the holes were not properly de-burred, allowing the bolt to loose tension. No use arguing with Slocumb though - you'll never get anything through his thick skull. You must have a tremendous amount of experience with nuts and bolts. As I mentioned I've been fooling with them things for about 70 years now and frankly I've never seen "numerous" head bolts fail. Yes, I've seen head bolts fail, but I would use the term "rarely" not "Numerous". I would have to say that if you have seen numerous head bolts fail then you are associating with some very incompetent mechanics. And how does one determine that they were under torqued after they have failed? Notb incompetent mechanics - but poor factory assembly. Don't take my word for the FACT the problem exists. See: http://www.croberts.com/bolt.htm In particular Picture #10. As for broken head bolts - see: https://www.bimmerforums.com/forum/s...ken-Head-Bolts Also see: http://www.boltscience.com/pages/Failure%20Modes.swf and: https://www.hiretorque.co.uk/failure...bolted-joints/ -Particularly item #3 3. Fatigue Failures Fatigue failures typically occur within a couple of threads, where the bolt engages into the internal thread. Failure is then reached due to the high stress gradient within the region. Fatigue failures can be particularly hazardous because they often occur with no visible warning signs and the failure is often sudden. Fatigue failures are often unknowingly avoided in gasketed joints simply because the required crush for the gasket often dictates a torque or bolt tension that minimizes the risk of a fatigue failure. However, changing to a new gasket type later on which requires less crush may be the initial cause of bolt fatigue failure. It is not unusual to assume that a bolt has failed due to overload when it has in fact failed from fatigue, which can also be a consequence of self-loosening. Also: http://www.bluetoad.com/article/Bolt...0/article.html and: http://www.onallcylinders.com/2014/0...ener-failures/ Also: https://www.excelcalcs.com/engineeri...-joints-fail?/ The first cause listed: Insufficient Clamp force? - Usually by applying a measured torque load to the nut bolted joints are tightened to achieve a specific clamp load. Even under the most extreme applied loads, the clamping force must prevent joint movement between clamped parts. Movement includes both opening of the joint to form gaps and slipping. Loads applied to the joint may be axial forces (in the direction of the bolt axis) and/or shear forces (perpendicular to the bolt axis). If slippage occurs then the joint may fail by the bolt loosening. If a gap in the joint opens then a bolt failure by fatigue is more likely to occur. Typically bolt fatigue failures occur because of insufficient preload rather than poor fatigue strength of the bolt. Improving the method of tightening can reduce the scatter in bolt preload and help guarantee the minimum required clamping force Pay particular attention to the sectionfollowing the "bolted joint.xls" link which explains things in pretty plain language. You may have worked on machines, including aircraft without fully understanding what you were doing or why. I have not only worked on cars and agricultural equipment and industrial equipment (loaders and dozers etc) and been rather extensively involved with amateur built/homebuilt/experimental aviation, I have also taught automotive mechanics at the secondary school AND post secondary (trade) level. I'm with Mr. Clare on all the info above. Those are good sources of information. This is something we used to cover in great detail in machine design classes. -- - Frank Krygowski |
Selecting An Appropriate Bolt
On Wednesday, April 19, 2017 at 10:37:18 PM UTC-7, Art Shapiro wrote:
On 4/17/2017 1:52 PM, Doug Landau wrote: Get a new stem. This one is a flawed design. There is built-in problem with the shape of the part, and that is a lack of remaining metal around the bolt hole. The stem has been made bigger around the front bolt hole to overcome this, but it still has the 2-bolt-1-failure problem. The traditional shape does not make this concession to ease-of-handlebar-change, and carefully places the single bolt in the rear where there is plenty of metal surrounding the threads. The traditional design is both less likely to experience a bolt failure, and - in the wild guess dept., be more likely to hold on to the bars and remain usable in the event that one does. I'm he OP. It so happens that the rear bolt was the one that snapped, which seems to contradict your assertion about the design's weak point. Art I disagree. The traditional design has a single bolt whereas yours has two.. Therefore your chances of experiencing a quill stem bolt failure are 2X those of the owner of a traditional quill stem. Doug |
Selecting An Appropriate Bolt
On Thursday, April 20, 2017 at 2:17:23 AM UTC-7, John B Slocomb wrote:
On Wed, 19 Apr 2017 22:37:15 -0700, Art Shapiro wrote: On 4/17/2017 1:52 PM, Doug Landau wrote: Get a new stem. This one is a flawed design. There is built-in problem with the shape of the part, and that is a lack of remaining metal around the bolt hole. The stem has been made bigger around the front bolt hole to overcome this, but it still has the 2-bolt-1-failure problem. The traditional shape does not make this concession to ease-of-handlebar-change, and carefully places the single bolt in the rear where there is plenty of metal surrounding the threads. The traditional design is both less likely to experience a bolt failure, and - in the wild guess dept., be more likely to hold on to the bars and remain usable in the event that one does. I'm he OP. It so happens that the rear bolt was the one that snapped, which seems to contradict your assertion about the design's weak point. Art And, if I remember correctly, after only 15 years too :-) This is false logic. There are at least 15 parts on your bike; by your policy we should expect catastrophic part failure once per year. |
Selecting An Appropriate Bolt
With all ofthe replies about just about everything else, did you get a definitive reply that ANSWERED your question about whether to use a Grade 5 or Grade 8 bolt? If it were me i'd use the strongest grade I could get. Cheers Yes, he did. Andy answered it definitively: Original handlebar clamp bolts are Grade 8 What more do you need to know? He then went on to prove it by arriving at the same answer with different logic: Grade 5 may be strong enough but for pennies difference I suggest an 8 He and then addressed the Ti question: I wouldn't use Ti fasteners in a stem but some guys do and many don't die. To arrive at this answer via different logic: Speedplay/x2 pedals in Titanium say "Not for riders over 175 Lbs". What else do you need to know? Yes I realize that the pedal shaft is a beam whereas the stem bolt is in tension. So what. That said, I still want a Habanero. -dkl |
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