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#42
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Selecting An Appropriate Bolt
On Wed, 19 Apr 2017 09:12:06 -0700 (PDT), wrote:
On Monday, April 17, 2017 at 8:29:53 PM UTC-7, John B Slocomb wrote: On Mon, 17 Apr 2017 16:19:15 -0700 (PDT), Doug Landau wrote: On Friday, April 14, 2017 at 11:11:18 AM UTC-7, Frank Krygowski wrote: On 4/14/2017 12:33 PM, jbeattie wrote: On Friday, April 14, 2017 at 7:27:06 AM UTC-7, AMuzi wrote: On 4/14/2017 9:14 AM, Art Shapiro wrote: On 4/14/2017 5:35 AM, AMuzi wrote: Original handlebar clamp bolts are Grade 8; readily available and cheap. Grade 5 may be strong enough but for pennies difference I suggest an 8. How does one get these "readily available" Grade 8 guys? Deda doesn't seem to have much of a web presence outside of Italy. Is this a generic item stocked by a good LBS? Any metric fastener supplier if not your local hardware store. https://duckduckgo.com/?q=DIN+912+grade+8&t=ha&ia=web My neighborhood hardware store has them: http://aboysupply.com/wp-content/upl...1024x415_c.png They have a crazy selection of fasteners. By the way, what's the deal with thread pitch? I always worry I'm getting the wrong pitch, but I guess that the whole "standard/fine/extra fine" thread pitch only kicks in with fasteners over 8mm(?). Otherwise, it's a pre-set. Right? No. It's just the charts that only kick in at 8. They are clearly both a)written by someone who doesn't actually know, themselves, and b)plagarising heavily from each other, and repeating the other's mistakes. There are metric fine pitch threads https://mdmetric.com/tech/thddat3.htm like 5mm-0.5 instead of 5mm-0.8 That chart is ****ed up. It says fine but lists more than one thread pitch in the first column, and inconsistently shows extra- and super-fine pitches instead. The commonly found standard M5 bolt is indeed 0.8 pitch, but the commonly found fine pitch M5 is 0.7. 0.5 must be extra-fine or super-fine. Which is why when you buy a tap and dies set it comes with 5-.8 and 5-.7 but not 5-.5. I think but am not 100% sure that M6 fine is 0.8 not 0.75. http://www.sears.com/craftsman-39-pc...g&gclsrc=aw.ds but I've hardly ever come across them in real life. No? Are you sure - you've never chased munged up pedal threads? Doing so sends you down to the hardware store for an M10-1.0 tap, because your tap and dies set comes with a 10-1.5 (standard) and 10-1.25 (fine). There is at least one other place where there is a fine thread, an 8, I think, and I think it's the brake pivot bolt, but am not sure I'm remembering correctly. What's the thread pitch of derailer hangers? The "fine thread - course thread" discussion if essentially a very simplistic categorizing of fasteners. The U.S. Unified thread system provides a sort of rationalization for a UNC/UNF series but that didn't and doesn't prevent fasteners being made in a large number of thread pitches. In U.S. sizes we have, for example, the 1/4"x20tpi (National Course), the 1/4 x 24 (NS), the 1/4 x 28 (NF), the 1/4 x 32 (NEF) and the 1/4 x 40 (NS). From memory the difference between American fine and course is the depth of the thread. Course threads cut much deeper into the mating piece to achieve the same amount of metal to metal contact as fine threads. They are both 60 degree threads but with a flat at the base and peak and I don't remember whether they are the same. Maybe Frank can check his Machinery's Handbook (if it is modern enough to include metric threads :-) |
#43
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Selecting An Appropriate Bolt
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#44
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Selecting An Appropriate Bolt
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. |
#45
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Selecting An Appropriate Bolt
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#46
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Selecting An Appropriate Bolt
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 |
#47
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Selecting An Appropriate Bolt
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. 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. |
#48
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Selecting An Appropriate Bolt
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 :-) |
#49
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Selecting An Appropriate Bolt
On 4/19/2017 10:56 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. +1 -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#50
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Selecting An Appropriate Bolt
On Wednesday, April 19, 2017 at 7:52:25 PM UTC-7, John B Slocomb wrote:
On Wed, 19 Apr 2017 09:12:06 -0700 (PDT), wrote: On Monday, April 17, 2017 at 8:29:53 PM UTC-7, John B Slocomb wrote: On Mon, 17 Apr 2017 16:19:15 -0700 (PDT), Doug Landau wrote: On Friday, April 14, 2017 at 11:11:18 AM UTC-7, Frank Krygowski wrote: On 4/14/2017 12:33 PM, jbeattie wrote: On Friday, April 14, 2017 at 7:27:06 AM UTC-7, AMuzi wrote: On 4/14/2017 9:14 AM, Art Shapiro wrote: On 4/14/2017 5:35 AM, AMuzi wrote: Original handlebar clamp bolts are Grade 8; readily available and cheap. Grade 5 may be strong enough but for pennies difference I suggest an 8. How does one get these "readily available" Grade 8 guys? Deda doesn't seem to have much of a web presence outside of Italy. Is this a generic item stocked by a good LBS? Any metric fastener supplier if not your local hardware store. https://duckduckgo.com/?q=DIN+912+grade+8&t=ha&ia=web My neighborhood hardware store has them: http://aboysupply.com/wp-content/upl...1024x415_c.png They have a crazy selection of fasteners. By the way, what's the deal with thread pitch? I always worry I'm getting the wrong pitch, but I guess that the whole "standard/fine/extra fine" thread pitch only kicks in with fasteners over 8mm(?). Otherwise, it's a pre-set. Right? No. It's just the charts that only kick in at 8. They are clearly both a)written by someone who doesn't actually know, themselves, and b)plagarising heavily from each other, and repeating the other's mistakes. There are metric fine pitch threads https://mdmetric.com/tech/thddat3.htm like 5mm-0.5 instead of 5mm-0.8 That chart is ****ed up. It says fine but lists more than one thread pitch in the first column, and inconsistently shows extra- and super-fine pitches instead. The commonly found standard M5 bolt is indeed 0.8 pitch, but the commonly found fine pitch M5 is 0.7. 0.5 must be extra-fine or super-fine. Which is why when you buy a tap and dies set it comes with 5-.8 and 5-.7 but not 5-.5. I think but am not 100% sure that M6 fine is 0.8 not 0.75. http://www.sears.com/craftsman-39-pc...g&gclsrc=aw.ds but I've hardly ever come across them in real life. No? Are you sure - you've never chased munged up pedal threads? Doing so sends you down to the hardware store for an M10-1.0 tap, because your tap and dies set comes with a 10-1.5 (standard) and 10-1.25 (fine). There is at least one other place where there is a fine thread, an 8, I think, and I think it's the brake pivot bolt, but am not sure I'm remembering correctly. What's the thread pitch of derailer hangers? The "fine thread - course thread" discussion if essentially a very simplistic categorizing of fasteners. The U.S. Unified thread system provides a sort of rationalization for a UNC/UNF series but that didn't and doesn't prevent fasteners being made in a large number of thread pitches. In U.S. sizes we have, for example, the 1/4"x20tpi (National Course), the 1/4 x 24 (NS), the 1/4 x 28 (NF), the 1/4 x 32 (NEF) and the 1/4 x 40 (NS). From memory the difference between American fine and course is the depth of the thread. Course threads cut much deeper into the mating piece to achieve the same amount of metal to metal contact as fine threads. They are both 60 degree threads but with a flat at the base and peak and I don't remember whether they are the same. Maybe Frank can check his Machinery's Handbook (if it is modern enough to include metric threads :-) Well, I'm just working from a not very good memory but course threads offer less actual bolt area inside of the threads and hence should not be torqued as high as a fine thread. |
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