SAE Grade-8 bolt snapped @135ft/lbs

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CarGuru > 4 x 4 > SAE Grade-8 bolt snapped @135ft/lbs 12 March 2005 18:29:08

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SAE Grade-8 bolt snapped @135ft/lbs
Ultralight 9 March 2005 06:03:31
	I'm dealing with a critical application. If these fasteners fail, the results could potentially be fatal. I need maximum security. I've been torquing 1/2" grade-8 bolts to 135ft/lbs. Tonight, one of the bolts snapped in half while torquing. This made me rethink all the other bolts that I've been torquing to this spec. First, shouldn't a 1/2" grade-8 bolt withstand far more than 135ft/lbs??? If not, I need a general torque spec that will ensure proper bolt tension. Remember, if these bolts fail or come loose, the results will not be pretty....
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Keith 9 March 2005 07:13:07 [ permanent link ]
	First of all, check this website http://www.rockcrawler.com/techreports/fasteners_torque/index.asp# and check out their torque calculator. From what it is saying, a 1/2" Grade 8 bolt should be torqued to 145 ft-lbs dry. I'm not sure why your bolts would be snapping in half since normally the head would come off from over-torquing. Of course you didn't say what application you were using the bolts for, but I can tell you that you need thread length engagement of 2.5 times the bolt diameter to ensure maximum holding capacity. Any longer than that has no additional effect. Remember also, that these bolts are made by the millions so it is entirely possible that a bad one could have slipped through. Also, if you are using nuts, make sure these are properly graded as well...
		Add comment


Ashton Crusher 9 March 2005 09:53:56 [ permanent link ]
	On 8 Mar 2005 19:13:07 -0800, "Keith" <keithalumbaugh@aol.com> wrote: First of all, check this website>http://www.rockcrawler.com/techreports/fasteners_torque/index.asp# and>check out their torque calculator. From what it is saying, a 1/2">Grade 8 bolt should be torqued to 145 ft-lbs dry. I'm not sure why>your bolts would be snapping in half since normally the head would come>off from over-torquing. Of course you didn't say what application you>were using the bolts for, but I can tell you that you need thread>length engagement of 2.5 times the bolt diameter to ensure maximum>holding capacity. Any longer than that has no additional effect.>Remember also, that these bolts are made by the millions so it is>entirely possible that a bad one could have slipped through. Also, if>you are using nuts, make sure these are properly graded as well... I'm not following the 2.5 x dia engagement length statement. If you used 1/2" bolts and normal sized nuts the engagement length in the nut would only be around 1/2" - 3/4" for typical nuts. How would you ever use a bolt and nut where you could get 2.5 x dia engagement? I can see it for putting head bolts or main caps on, they have drilled and tapped holes of decent length.
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SBlackfoot 9 March 2005 11:17:24 [ permanent link ]
	How would you ever use a bolt and nut where you could get 2.5 x dia engagement? A jam-nut?
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David Ward 10 March 2005 02:35:21 [ permanent link ]
	"ultralight" <Cpeters1@adelphia.net> wrote in message news:1110333811.576638.195480@z14g2000cwz.googlegroups.com... : I'm dealing with a critical application. If these fasteners fail, the : results could potentially be fatal. I need maximum security. I've been : torquing 1/2" grade-8 bolts to 135ft/lbs. Tonight, one of the bolts : snapped in half while torquing. This made me rethink all the other : bolts that I've been torquing to this spec. First, shouldn't a 1/2" : grade-8 bolt withstand far more than 135ft/lbs??? If not, I need a : general torque spec that will ensure proper bolt tension. Remember, if : these bolts fail or come loose, the results will not be pretty.... : I looked at: http://www.boltdepot.com/fastener-information/US-Recommended-Torque.htm and it says you're overtorqueing by quite a bit. Whatcha usin' it for? Curiosity got me. Dave
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Keith 10 March 2005 08:35:10 [ permanent link ]
	Well, he never did say what his application was, and if he was using nuts or not. I was just adding the 2.5 times diameter rule just for his general knowledge... Although I'm sure everyone already knows that anyway. It's also better to torque in stages when using a higher torque amount. Either way, for maximum security, I would get a bolt with a rolled thread made from material that has been certified and NDT tested. It would add a few bucks to the cost, but you can guarantee the bolt will be harder to snap than any 10 cent hardware store Grade-8 "Made in China" bolt. This website explains the difference: http://www.lancasterthreaded.com/docs/tensile.htm
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Guest 10 March 2005 08:56:36 [ permanent link ]
	A grade 8 bolt is only a grade 8 bolt if you know who made it. There has always been a problem in my lifetime of counterfeit and cheap import bolts that are marked as one grade, but don't make the grade. In mission critical applications (aircraft, bridges, etc), the manufacturer of the equipment does independent testing of random samples of the fasteners. As others have noted, buy from a quality manufacturer of rolled-thread bolts. Tables I have in my shop show 90 ft/lbs for plated grade 8 (the common yellowish ones), 115 ft/lbs for unplated. There are also grades above 8, like 8.2 and ASTM A490. You probably don't need this though, a snap a 135ft/lbs indicates that you're most likely the victim of a sub-standard import bolt. -Adam
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Will Honea 10 March 2005 11:41:39 [ permanent link ]
	On Thu, 10 Mar 2005 04:56:36 UTC diaphone@gmail.com wrote: A grade 8 bolt is only a grade 8 bolt if you know who made it. There> has always been a problem in my lifetime of counterfeit and cheap> import bolts that are marked as one grade, but don't make the grade. In> mission critical applications (aircraft, bridges, etc), the> manufacturer of the equipment does independent testing of random> samples of the fasteners.> As others have noted, buy from a quality manufacturer of rolled-thread> bolts. Tables I have in my shop show 90 ft/lbs for plated grade 8 (the> common yellowish ones), 115 ft/lbs for unplated. There are also grades> above 8, like 8.2 and ASTM A490. You probably don't need this though, a> snap a 135ft/lbs indicates that you're most likely the victim of a> sub-standard import bolt. There's also a question of fatigue if the bolt had been used at max torque before. I had one head where the grade 8 bolts used to hold the cam assembly were specified for one time use only. Being a bit skeptical, I played it with and sure enough the darned bolts would begin to stretch, neck down and finally break after 5-6 cycles if I let them set for a day or so between removals. -- Will Honea
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C. E. White 10 March 2005 18:44:04 [ permanent link ]
	ultralight wrote:> I'm dealing with a critical application. If these fasteners fail, the> results could potentially be fatal. I need maximum security. I've been> torquing 1/2" grade-8 bolts to 135ft/lbs. Tonight, one of the bolts> snapped in half while torquing. This made me rethink all the other> bolts that I've been torquing to this spec. First, shouldn't a 1/2"> grade-8 bolt withstand far more than 135ft/lbs??? If not, I need a> general torque spec that will ensure proper bolt tension. Remember, if> these bolts fail or come loose, the results will not be pretty.... 135 ft-lbs to too high a torque for a 1/2" grade 8 bolt. I assume you are torquing them dry. If you are lubricating the bolts, then 135 ft-lbs is way to high. http://www.futek.com/boltcalc.asp http://www.assemblymag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,6493,99794,00.html http://dodgeram.org/tech/specs/bolts/SAE_bolts.html http://www.boltdepot.com/fastener-information/US-Recommended-Torque.htm http://www.boltdepot.com/fastener-information/Bolt-Grade-Chart.aspx http://www.futek.com/files/Pdf/Manuals%20and%20Technical%20Documents/Bolt%20Torque%20Equations.pdf Ed
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Guest 11 March 2005 03:50:51 [ permanent link ]
	Please tell me you are useing a CALIBRATED torque wrench. Matt
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Guest 11 March 2005 04:01:45 [ permanent link ]
	You are kidding, right? You are tightening bolts, which could be fatal if they break "by feel" ? Why wouldnt you consult a torque spec BEFORE you even torque any of these bolts? The next question is: What sort of load is on these bolts? If they survive your torqueing habbits, will they hold up to the load you are putting on? Matt
		Add comment


Mike Romain 11 March 2005 18:52:40 [ permanent link ]
	Good lord, do the other folks that have to fly near him know he has 0 for a clue? No I take that back. He is a Darwin Award candidate, they have less than 0 for a clue. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's web1000@shaw.ca wrote:> You are kidding, right?> You are tightening bolts, which could be fatal if they break "by feel"> ? Why wouldnt you consult a torque spec BEFORE you even torque any of> these bolts?> The next question is: What sort of load is on these bolts? If they> survive your torqueing habbits, will they hold up to the load you are> putting on?> Matt
		Add comment


Peter D . Hipson 12 March 2005 18:29:08 [ permanent link ]
	The reply that generated this second half of the thread didn't make it to my news server, and no one has quoted it... If someone has it could you please re-post! On Fri, 11 Mar 2005 09:52:40 -0500, Mike Romain <romainm@sympatico.ca> wrote: Good lord, do the other folks that have to fly near him know he has 0>for a clue?> No I take that back. He is a Darwin Award candidate, they have less>than 0 for a clue.> Mike>86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00>88 Cherokee 235 BFG AT's> web1000@shaw.ca wrote:>> You are kidding, right?>> You are tightening bolts, which could be fatal if they break "by feel">> ? Why wouldnt you consult a torque spec BEFORE you even torque any of>> these bolts?>> The next question is: What sort of load is on these bolts? If they>> survive your torqueing habbits, will they hold up to the load you are>> putting on?>> Matt
		Add comment

CarGuru > 4 x 4 > SAE Grade-8 bolt snapped @135ft/lbs 12 March 2005 18:29:08

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SAE Grade-8 bolt snapped @135ft/lbs

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