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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Are higher grade bolts more brittle?
Howdy,
I recently purchased some (metric) bolts to attach a receiver hitch to my Jeep. While the factory doesn't specify the grade, the nuts they go into have a six (or possibly a 60) on them. I didn't purchase the bolts from the stealership, because they want $11.00 (eleven dollars) *per* bolt, so I bought them from Fastenal instead. When I bought the bolts, I got them in a grade 10.9 (metric). Earlier today, I came across a discussion on a Jeep forum where someone alluded to their belief that higher grade bolts would be too "brittle" for this application. Personally, I think I'm going to be just fine, but I know someone here will have something more substantial than my gut feeling. So, do you think I should order some different bolts, or will I likely be just fine with the ones I already have?. Thanks, Jon |
#2
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Are higher grade bolts more brittle?
Grade 10.9
Ultimate Tensile Strength 10MPa Carbon Content 0.9% This is a very strong bolt. If your application calls for a high tensile bolt then this is a good choice. You could go for a Grade 12, but this might be overkill. If the nuts are old, you should think about getting new ones. HTH Dom. |
#3
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Are higher grade bolts more brittle?
On Jan 14, 5:54 pm, "Jon Danniken"
wrote: Howdy, I recently purchased some (metric) bolts to attach a receiver hitch to my Jeep. While the factory doesn't specify the grade, the nuts they go into have a six (or possibly a 60) on them. I didn't purchase the bolts from the stealership, because they want $11.00 (eleven dollars) *per* bolt, so I bought them from Fastenal instead. When I bought the bolts, I got them in a grade 10.9 (metric). Earlier today, I came across a discussion on a Jeep forum where someone alluded to their belief that higher grade bolts would be too "brittle" for this application. Personally, I think I'm going to be just fine, but I know someone here will have something more substantial than my gut feeling. So, do you think I should order some different bolts, or will I likely be just fine with the ones I already have?. Thanks, Jon Of course, the bolts aren't supposed to be taking the shear load, but that's in a perfect world. Dave |
#4
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Are higher grade bolts more brittle?
Dom wrote:
Grade 10.9 Ultimate Tensile Strength 10MPa Carbon Content 0.9% This is a very strong bolt. If your application calls for a high tensile bolt then this is a good choice. You could go for a Grade 12, but this might be overkill. If the nuts are old, you should think about getting new ones. HTH Dom. The 1st figure is 1/10 the tensile strength and 2nd figure is 1/10 the ratio between the minimum tensile strength and the minimum yield stress (or proof stress in the higher strength fasteners as this is), also IIRC the units are in kgf/mm2. So the yield stress is 90 kgf/mm2 and the tensile strength is 100kgf/mm2. Not sure what the US equivalent is but a standard socket cap in the UK is a 12.9, button head is 10.9. IIRC the socket cap screw in the US have equivalent characteristics to 12.9, and I think you have an equivalanet to 10.9 also. |
#5
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Are higher grade bolts more brittle?
On Mon, 14 Jan 2008 14:54:01 -0800, Jon Danniken wrote:
Howdy, I recently purchased some (metric) bolts to attach a receiver hitch to my Jeep. While the factory doesn't specify the grade, the nuts they go into have a six (or possibly a 60) on them. I didn't purchase the bolts from the stealership, because they want $11.00 (eleven dollars) *per* bolt, so I bought them from Fastenal instead. When I bought the bolts, I got them in a grade 10.9 (metric). Earlier today, I came across a discussion on a Jeep forum where someone alluded to their belief that higher grade bolts would be too "brittle" for this application. Personally, I think I'm going to be just fine, but I know someone here will have something more substantial than my gut feeling. So, do you think I should order some different bolts, or will I likely be just fine with the ones I already have?. Thanks, Jon Higher carbon steels that are hardened as much as they'll take are much more likely to break, rather than bend. El cheapo "high strength" bolts that are _improperly_ hardened are much more likely to break than good ones that are tempered properly. If a bend is a bad thing and a break is a disaster, a lower grade bolt may be indicated, or just sucking it up and buying from the dealership. I'd try to find out the grade of bolt called out by Jeep, and buy that, from a reputable source. -- Tim Wescott Control systems and communications consulting http://www.wescottdesign.com Need to learn how to apply control theory in your embedded system? "Applied Control Theory for Embedded Systems" by Tim Wescott Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html |
#6
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Are higher grade bolts more brittle?
The usual argument among the off road groups is that the lower grade (US
grade 5) bolts bend rather than break like the higher grade (US grade 8) bolts. That's true but the grade 8 bolts take more stress than the grade 5 bolts do before they break. The off roaders like the bolts that bend, it gives them a visual cue that they are about to do destructive things to their rigs. But that means that the bolts that hold (and bend) are the lower level items. And the argument goes on. Jon Danniken wrote: Howdy, I recently purchased some (metric) bolts to attach a receiver hitch to my Jeep. While the factory doesn't specify the grade, the nuts they go into have a six (or possibly a 60) on them. I didn't purchase the bolts from the stealership, because they want $11.00 (eleven dollars) *per* bolt, so I bought them from Fastenal instead. When I bought the bolts, I got them in a grade 10.9 (metric). Earlier today, I came across a discussion on a Jeep forum where someone alluded to their belief that higher grade bolts would be too "brittle" for this application. Personally, I think I'm going to be just fine, but I know someone here will have something more substantial than my gut feeling. So, do you think I should order some different bolts, or will I likely be just fine with the ones I already have?. Thanks, Jon |
#7
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Are higher grade bolts more brittle?
"Dom" wrote in message ... Grade 10.9 Ultimate Tensile Strength 10MPa Carbon Content 0.9% This is a very strong bolt. If your application calls for a high tensile bolt then this is a good choice. You could go for a Grade 12, but this might be overkill. If the nuts are old, you should think about getting new ones. HTH Dom. I agree! My nuts are getting old and I'm thinking about getting new ones... |
#8
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Are higher grade bolts more brittle?
"Jon Danniken" wrote:
I didn't purchase the bolts from the stealership, because they want $11.00 (eleven dollars) *per* bolt, so I bought them from Fastenal instead. When I bought the bolts, I got them in a grade 10.9 (metric). I'd worry about other stuff in life. The important thing is that the clamping surfaces are parallel. Wes |
#9
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Are higher grade bolts more brittle?
Jon Danniken wrote:
While the factory doesn't specify the grade, the nuts they go into have a six (or possibly a 60) on them. That's grade 6. Standard is grade 8. The mating strength for a bolt would be grade 8.8. Grade 10.9 is just a waste of money. Sure, they are more brittle (they can't be *stretched* as much before they fail) but there is no construction that requires a *plastic* stretch. So it is OK. Nick -- The lowcost-DRO: http://www.yadro.de |
#10
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Are higher grade bolts more brittle?
David Billington wrote:
The 1st figure is 1/10 the tensile strength and 2nd figure is 1/10 the ratio between the minimum tensile strength and the minimum yield stress (or proof stress in the higher strength fasteners as this is), also IIRC the units are in kgf/mm2. So the yield stress is 90 kgf/mm2 and the tensile strength is 100kgf/mm2. Grade 10.9 means: tensile strength is 100 kp / mm^2 (there is no such thing as kgf) Multiplying the first number with the second (10 * 9 = 900) gives the yield strength times 10 (so 90 kp / mm ^2). A 8.8 has 80 kp/mm^2 tensile and 64 kp/mm^2 yield strength. The numbers aren't very precise. That was the initial definition. Of course, the units now are in N and mm, or in Pa. Nick -- The lowcost-DRO: http://www.yadro.de |
#11
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Are higher grade bolts more brittle?
Nick Mueller wrote:
David Billington wrote: The 1st figure is 1/10 the tensile strength and 2nd figure is 1/10 the ratio between the minimum tensile strength and the minimum yield stress (or proof stress in the higher strength fasteners as this is), also IIRC the units are in kgf/mm2. So the yield stress is 90 kgf/mm2 and the tensile strength is 100kgf/mm2. Grade 10.9 means: tensile strength is 100 kp / mm^2 (there is no such thing as kgf) I ran across kgf not being an official unit the other day but still widely used in some places. The tensile and compressive test stand software I work on sometimes supports kgf, gf, as well as N, kN, MPa, kPa, N/mm^2, lbf and a few others. The N/mm^2 was added recently to suit customer demand, although it is equivalent to kPa, some customers knew that but still asked for N/mm^2 as that was what they were used to. Likewise some parts of the world still use kgf. What is the status of daN. I have run across it a few times before and finally looks it up, as I didn't know what it was, decanewton 1daN = 10N. Now the data sheets make sense. Multiplying the first number with the second (10 * 9 = 900) gives the yield strength times 10 (so 90 kp / mm ^2). A 8.8 has 80 kp/mm^2 tensile and 64 kp/mm^2 yield strength. The numbers aren't very precise. That was the initial definition. Of course, the units now are in N and mm, or in Pa. Nick |
#12
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Are higher grade bolts more brittle?
On Mon, 14 Jan 2008 21:55:07 -0600, RoyJ
wrote: The usual argument among the off road groups is that the lower grade (US grade 5) bolts bend rather than break like the higher grade (US grade 8) bolts. That's true but the grade 8 bolts take more stress than the grade 5 bolts do before they break. The off roaders like the bolts that bend, it gives them a visual cue that they are about to do destructive things to their rigs. But that means that the bolts that hold (and bend) are the lower level items. And the argument goes on. This brings to mind a question I have had for a long time. Our local supply store (USA) carries Grade 8 (gold), Grade 5 (gray), and the common (standard-silver) bolts. My question is what grade are the common bolts? Or dont they grade them? What is the difference in strength between Grade 8, Grade 5 and common bolts? Is there a website or file I can download with all the facts? (Please use american definations, (such as POUNDS) not metric. I dont understand metrics..... To me, killagram sounds like murder and is far too violent for my tastes.) |
#13
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Are higher grade bolts more brittle?
David Billington wrote:
What is the status of daN. I have run across it a few times before and finally looks it up, as I didn't know what it was, decanewton 1daN = 10N. Now the data sheets make sense. That is legal. da (deca) is the multiplier (10) and N the unit (Newton). But at least here in Germany daN is very rare. Anyhow, the reason why it might be used is that the number is almost (0.981) the same as kp (no more legal, non-SI). The reason why people stick to N/mm^2 is, that the numbers are more handy compared to the Pa (N/m^2). Also, math in mechanical engineering often enough is done in mm and not in m, as dimensions are in mm. Anyhow, all can well be scaled and there is no conversion with weird factors. Just a thing of convenience, just depends on how you prefer to calculate. Nick -- The lowcost-DRO: http://www.yadro.de |
#14
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Are higher grade bolts more brittle?
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#15
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Are higher grade bolts more brittle?
On Tue, 15 Jan 2008 05:26:45 GMT, with neither quill nor qualm, "Tom
Gardner" quickly quoth: "Dom" wrote in message ... Grade 10.9 Ultimate Tensile Strength 10MPa Carbon Content 0.9% This is a very strong bolt. If your application calls for a high tensile bolt then this is a good choice. You could go for a Grade 12, but this might be overkill. If the nuts are old, you should think about getting new ones. HTH Dom. I agree! My nuts are getting old and I'm thinking about getting new ones... Um...what's a lesbian doing with nuts, pray tell? ----- = Dain Bramaged...but having lots of fun! = |
#16
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Are higher grade bolts more brittle?
Nick Mueller wrote:
David Billington wrote: What is the status of daN. I have run across it a few times before and finally looks it up, as I didn't know what it was, decanewton 1daN = 10N. Now the data sheets make sense. That is legal. da (deca) is the multiplier (10) and N the unit (Newton). But at least here in Germany daN is very rare. Anyhow, the reason why it might be used is that the number is almost (0.981) the same as kp (no more legal, non-SI). I was aware of the prefixes such as deca, deci etc but had not run across the abbreviation such as in daN. The only place I can recall seeing it in the UK was on the RS site www.rswww.com when looking for vibration isolation mounts. I annoyed me enough the other day that I looked up what it was so the data sheet made sense, now I might consider using some if needed. Having done physics in high school in the US (all SI metric) and an engineering degree in the UK, I could not recall ever seeing daN before, always N, kg, mm, m etc. In the same way I had only recently run across kgf used so had to check what it was, always seen kg before. At least I have never had the pleasure of foot, poundals, and slugs, as one of the guys on my engineering course did. He got a year placement working at a US aerospace company that used foot, poundals, and slugs. He, having been educated entirely in the UK, had never heard of them before as they had gone out of use in the UK. The reason why people stick to N/mm^2 is, that the numbers are more handy compared to the Pa (N/m^2). Also, math in mechanical engineering often enough is done in mm and not in m, as dimensions are in mm. Anyhow, all can well be scaled and there is no conversion with weird factors. Just a thing of convenience, just depends on how you prefer to calculate. Nick |
#17
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Are higher grade bolts more brittle?
On Jan 14, 5:54 pm, "Jon Danniken"
wrote: Howdy, I recently purchased some (metric) bolts to attach a receiver hitch to my Jeep. While the factory doesn't specify the grade, the nuts they go into have a six (or possibly a 60) on them. I didn't purchase the bolts from the stealership, because they want $11.00 (eleven dollars) *per* bolt, so I bought them from Fastenal instead. When I bought the bolts, I got them in a grade 10.9 (metric). Earlier today, I came across a discussion on a Jeep forum where someone alluded to their belief that higher grade bolts would be too "brittle" for this application. Personally, I think I'm going to be just fine, but I know someone here will have something more substantial than my gut feeling. So, do you think I should order some different bolts, or will I likely be just fine with the ones I already have?. Thanks, Jon I google'd "grade 8 bolts brittle", and found this article that seems pretty informative. The author is a Senior Staff Mechanical Engineer for Lockheed Martin (DAMHIKT) http://www.rockcrawler.com/techrepor...ners/index.asp Go with the grade 8. Carl Boyd |
#18
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Are higher grade bolts more brittle?
David Billington wrote:
In the same way I had only recently run across kgf used so had to check what it was I think it is an invention of the US. A desperate abuse to adopt the logical SI units to the US-awkwardness like poundforce and such. ;-) Nick -- The lowcost-DRO: http://www.yadro.de |
#19
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Are higher grade bolts more brittle?
Nick Mueller wrote:
wrote: To me, killagram sounds like murder and is far too violent for my tastes. How about the right spelling? It is "kilogram"! Kilo means thousand and stems from khilioi in Greek, gram or gramme is from the Greek/Latin word gramma Or is that too much culture for your taste? Nick Evidently absolutely no sense of humor. :-) ...lew... |
#20
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Are higher grade bolts more brittle?
Lew Hartswick wrote:
Nick Mueller wrote: wrote: To me, killagram sounds like murder and is far too violent for my tastes. How about the right spelling? It is "kilogram"! Kilo means thousand and stems from khilioi in Greek, gram or gramme is from the Greek/Latin word gramma Or is that too much culture for your taste? Nick Evidently absolutely no sense of humor. :-) ...lew... I expect a killergram is when the western union hitman shows up at your door. |
#21
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Are higher grade bolts more brittle?
This brings to mind a question I have had for a long time.
Our local supply store (USA) carries Grade 8 (gold), Grade 5 (gray), and the common (standard-silver) bolts. My question is what grade are the common bolts? Or dont they grade them? Unmarked bolts are usually grade 3, or worse. |
#22
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Are higher grade bolts more brittle?
Lew Hartswick wrote:
Or is that too much culture for your taste? Evidently absolutely no sense of humor. :-) Oh, I forgot to put a ;-) behind my last sentence. ;-) Nick -- The lowcost-DRO: http://www.yadro.de |
#23
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Are higher grade bolts more brittle?
"RoyJ" wrote:
The usual argument among the off road groups is that the lower grade (US grade 5) bolts bend rather than break like the higher grade (US grade 8) bolts. That's true but the grade 8 bolts take more stress than the grade 5 bolts do before they break. The off roaders like the bolts that bend, it gives them a visual cue that they are about to do destructive things to their rigs. But that means that the bolts that hold (and bend) are the lower level items. And the argument goes on. Thanks, Roy, that puts it into a good perspective. Jon |
#24
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Are higher grade bolts more brittle?
"Nick Mueller" wrote in message
... Jon Danniken wrote: While the factory doesn't specify the grade, the nuts they go into have a six (or possibly a 60) on them. That's grade 6. Standard is grade 8. The mating strength for a bolt would be grade 8.8. Grade 10.9 is just a waste of money. Sure, they are more brittle (they can't be *stretched* as much before they fail) but there is no construction that requires a *plastic* stretch. So it is OK. Thanks, Nick, I was a bit confused on the nomenclature of the metric fastners. Much appreciated! Jon |
#25
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Are higher grade bolts more brittle?
"Carl" wrote:
I google'd "grade 8 bolts brittle", and found this article that seems pretty informative. The author is a Senior Staff Mechanical Engineer for Lockheed Martin (DAMHIKT) http://www.rockcrawler.com/techrepor...ners/index.asp Go with the grade 8. Great article, thanks Carl! Jon |
#26
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Are higher grade bolts more brittle?
"Stupendous Man" wrote:
This brings to mind a question I have had for a long time. Our local supply store (USA) carries Grade 8 (gold), Grade 5 (gray), and the common (standard-silver) bolts. My question is what grade are the common bolts? Or dont they grade them? Unmarked bolts are usually grade 3, or worse. I made the mistake of buying a bunch of the 1/4" bolts out of the bulk bin at Home Despot a few years ago. They came apart tightening them with a 1/4" ratchet drive, and looked like pot metal on the inside. I don't look to HD for fastners anymore. Jon |
#27
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Are higher grade bolts more brittle?
On 2008-01-15, Jon Danniken wrote:
"Stupendous Man" wrote: This brings to mind a question I have had for a long time. Our local supply store (USA) carries Grade 8 (gold), Grade 5 (gray), and the common (standard-silver) bolts. My question is what grade are the common bolts? Or dont they grade them? Unmarked bolts are usually grade 3, or worse. I made the mistake of buying a bunch of the 1/4" bolts out of the bulk bin at Home Despot a few years ago. They came apart tightening them with a 1/4" ratchet drive, and looked like pot metal on the inside. I don't look to HD for fastners anymore. Jon I buy bolts at McMaster, they are slightly cheaper than Home Depot and I never had quality problems with them. i |
#28
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Are higher grade bolts more brittle?
On Tue, 15 Jan 2008 04:17:25 -0800, Larry Jaques
wrote: On Tue, 15 Jan 2008 05:26:45 GMT, with neither quill nor qualm, "Tom Gardner" quickly quoth: "Dom" wrote in message ... Grade 10.9 Ultimate Tensile Strength 10MPa Carbon Content 0.9% This is a very strong bolt. If your application calls for a high tensile bolt then this is a good choice. You could go for a Grade 12, but this might be overkill. If the nuts are old, you should think about getting new ones. HTH Dom. I agree! My nuts are getting old and I'm thinking about getting new ones... Um...what's a lesbian doing with nuts, pray tell? Got em hanging from the mirror of her Volvo. Gunner ----- = Dain Bramaged...but having lots of fun! = |
#29
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Are higher grade bolts more brittle?
On Tue, 15 Jan 2008 14:01:54 +0000, David Billington
wrote: Lew Hartswick wrote: Nick Mueller wrote: wrote: To me, killagram sounds like murder and is far too violent for my tastes. How about the right spelling? It is "kilogram"! Kilo means thousand and stems from khilioi in Greek, gram or gramme is from the Greek/Latin word gramma Or is that too much culture for your taste? Nick Evidently absolutely no sense of humor. :-) ...lew... I expect a killergram is when the western union hitman shows up at your door. "Candygram for Mr. Mongo...Candygram for Mr. Mongo...." Gunner |
#30
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Are higher grade bolts more brittle?
Gunner wrote in
: snip "Candygram for Mr. Mongo...Candygram for Mr. Mongo...." Gunner I just hope he got credit for that..... Bill |
#31
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Are higher grade bolts more brittle?
On Tue, 15 Jan 2008 07:10:14 -0800, "Jon Danniken"
wrote: "Stupendous Man" wrote: This brings to mind a question I have had for a long time. Our local supply store (USA) carries Grade 8 (gold), Grade 5 (gray), and the common (standard-silver) bolts. My question is what grade are the common bolts? Or dont they grade them? Unmarked bolts are usually grade 3, or worse. I made the mistake of buying a bunch of the 1/4" bolts out of the bulk bin at Home Despot a few years ago. They came apart tightening them with a 1/4" ratchet drive, and looked like pot metal on the inside. I don't look to HD for fastners anymore. Jon I'm a farmer and my tractor loader was always breaking bolts. THey are constatly lifting one ton hay bales, pushing heavy snow and dirt, and all sorts of hard work. Last summer I got fed up with breaking down in the middle of jobs, often out in the field. I removed every bolt from the loader and one by one replaced them with grade 8 bolts and nuts. I wanted to put locking insert nuts on bolts that tend to loosen, but could not find them in grade 8, so I used common grade 8 nuts, and put the standard locking nuts on top. I have not had one single breakdown since. It may have cost twice as much as regular bolts, but it sure beats the hassles I was having and likely paid for itself the first time I used the loader because I didn't damage anything. For example I was lifting a large hay bale onto my pickup a couple years ago, when the bucket snapped a few bolts and the bale fell and busted off my tailgate. I dont even bother to buy regular bolts anymore for machinery. I only use them for decorative steel items and bolting stuff to wood. My only concern about the grade 8 bolts are how hard they will be to grind off if I ever have to remove one that rusted. I have never done it, but it's easy to use a grinder on a common bolt, but wonder how well those grade 8s grind off???? I dont have a cutting torch. |
#32
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Are higher grade bolts more brittle?
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#33
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Are higher grade bolts more brittle?
Nick Mueller wrote:
Jon Danniken wrote: While the factory doesn't specify the grade, the nuts they go into have a six (or possibly a 60) on them. That's grade 6. Standard is grade 8. The mating strength for a bolt would be grade 8.8. Grade 10.9 is just a waste of money. Sure, they are more brittle (they can't be *stretched* as much before they fail) but there is no construction that requires a *plastic* stretch. So it is OK. Nick I disagree with the "no construction that requires a *plastic* stretch" part. That's a common requirement in almost all aircraft construction. Richard |
#34
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Are higher grade bolts more brittle?
cavelamb himself wrote:
I disagree with the "no construction that requires a *plastic* stretch" part. That's a common requirement in almost all aircraft construction. With screws!? Nick -- The lowcost-DRO: http://www.yadro.de |
#35
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Are higher grade bolts more brittle?
Jon Danniken wrote:
I recently purchased some (metric) bolts to attach a receiver hitch to my Jeep. While the factory doesn't specify the grade, the nuts they go into have a six (or possibly a 60) on them. I didn't purchase the bolts from the stealership, because they want $11.00 (eleven dollars) *per* bolt, so I bought them from Fastenal instead. When I bought the bolts, I got them in a grade 10.9 (metric). Earlier today, I came across a discussion on a Jeep forum where someone alluded to their belief that higher grade bolts would be too "brittle" for this application. Personally, I think I'm going to be just fine, but I know someone here will have something more substantial than my gut feeling. So, do you think I should order some different bolts, or will I likely be just fine with the ones I already have? Yes. In general, as you increase the yield stress of steel by alloying there is a reduction in its ductility. This causes a reduction in the fracture toughness (the amount of energy required to turn a small crack into a large one), which manifests itself as increased brittleness. However, it's much harder to say how much the brittleness will increase. It may or may not be significant in your case. You could try bending one of the bolts if they are of a fairly small diameter. If you can make a large bend in the bolt before it breaks the brittleness probably isn't going to matter. Best wishes, Chris |
#36
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Are higher grade bolts more brittle?
Jon Danniken wrote:
"Carl" wrote: I google'd "grade 8 bolts brittle", and found this article that seems pretty informative. The author is a Senior Staff Mechanical Engineer for Lockheed Martin (DAMHIKT) http://www.rockcrawler.com/techrepor...ners/index.asp Go with the grade 8. Great article, thanks Carl! That article is quite right that brittleness is relative, and that materials are only usually thought of as brittle when they fracture before reaching their elastic limit. Even the most brittle steel isn't as brittle as glass. Best wishes, Chris |
#37
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Are higher grade bolts more brittle?
Christopher Tidy wrote:
Jon Danniken wrote: "Carl" wrote: I google'd "grade 8 bolts brittle", and found this article that seems pretty informative. The author is a Senior Staff Mechanical Engineer for Lockheed Martin (DAMHIKT) http://www.rockcrawler.com/techrepor...ners/index.asp Go with the grade 8. Great article, thanks Carl! That article is quite right that brittleness is relative, and that materials are only usually thought of as brittle when they fracture before reaching their elastic limit. Even the most brittle steel isn't as brittle as glass. Best wishes, Chris Then I seem to remember that for glass the brittleness only comes into effect when the thickness of the piece exceeds the critical crack length of the material, hence the reason that glass fibre exhibits the properties it does, its diameter is less than the critical crack length. |
#38
Posted to rec.crafts.metalworking
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Are higher grade bolts more brittle?
David Billington wrote:
Christopher Tidy wrote: Jon Danniken wrote: "Carl" wrote: I google'd "grade 8 bolts brittle", and found this article that seems pretty informative. The author is a Senior Staff Mechanical Engineer for Lockheed Martin (DAMHIKT) http://www.rockcrawler.com/techrepor...ners/index.asp Go with the grade 8. Great article, thanks Carl! That article is quite right that brittleness is relative, and that materials are only usually thought of as brittle when they fracture before reaching their elastic limit. Even the most brittle steel isn't as brittle as glass. Best wishes, Chris Then I seem to remember that for glass the brittleness only comes into effect when the thickness of the piece exceeds the critical crack length of the material, hence the reason that glass fibre exhibits the properties it does, its diameter is less than the critical crack length. Not sure about this. Won't the critical crack length depend on the stress the material is under? The fibres in glass fibre are very flexible because they're very thin, but I've never actually tried to break a single fibre. I'll have to try it sometime. Also, when a crack begins to grow in a composite made of glass fibre and resin, it will turn and travel sideways along the boundary between the resin and the fibre. This increases the fracture toughness. Best wishes, Chris |
#39
Posted to rec.crafts.metalworking
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Are higher grade bolts more brittle?
Stupendous Man wrote:
This brings to mind a question I have had for a long time. Our local supply store (USA) carries Grade 8 (gold), Grade 5 (gray), and the common (standard-silver) bolts. My question is what grade are the common bolts? Or dont they grade them? Unmarked bolts are usually grade 3, or worse. I'd guess they flunked Kindergarden. (for Nick: "Thats a joke son") ...lew... |
#40
Posted to rec.crafts.metalworking
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Are higher grade bolts more brittle?
Nick Mueller wrote:
cavelamb himself wrote: I disagree with the "no construction that requires a *plastic* stretch" part. That's a common requirement in almost all aircraft construction. With screws!? Nick Looks like he was talking about bolts - not screws. ??? Richard |
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