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Threads, Lubricants, and Torques: Home Mechanics Alert
#1
M
motoman
M
motoman
If you are concerned about corrosion and removal of a bolt or nut, you may have cleaned,lubricated and then torqued the fastener as usual , maybe by the torque settting in the owner's or workshop manual. Welcome to the world of limited information.
Almost all torque callouts are for dry , clean threads. When you lubricate and tighten to your favorite torque you are probably over -tightening by up to 45% (yes forty-five percent). This stresses the fastener toward its elastic limit where it looses clamping ability, necks down, work hardens and distorts threads. Sometimes you can see this with the naked eye. Do not reuse over- torqued fasteners
In this forum the most obvious fasteners subject to concern must be blade bolts and nuts. They are usually corroded or rusty on the outside and hard to get off , especially if not frequently removed.
Look at the charts below carefully . If you dip that clean dry 7/16 " x 20 bolt into motor oil the dry torque of 78 ft lbs should be reduced to about 55 ft lbs. If you use graphite/oil the figure should be reduced to 42 ft. lbs. Note this chart is for Grade 8 fasteners. People are usually concerned about spark plugs into aluminum heads. The plugs are often plated. A dab of motor oil and 15 ft lbs should be reduced to 10-11 ft lbs. If you dont' have a starting point on your fastener read the head marking in the diameter you have and put the these tables on your shop wall (Hot Rod Magazine 1970's). PS 12-27, The authors mentioned that lock tite has very little effect on torque.
Almost all torque callouts are for dry , clean threads. When you lubricate and tighten to your favorite torque you are probably over -tightening by up to 45% (yes forty-five percent). This stresses the fastener toward its elastic limit where it looses clamping ability, necks down, work hardens and distorts threads. Sometimes you can see this with the naked eye. Do not reuse over- torqued fasteners
In this forum the most obvious fasteners subject to concern must be blade bolts and nuts. They are usually corroded or rusty on the outside and hard to get off , especially if not frequently removed.
Look at the charts below carefully . If you dip that clean dry 7/16 " x 20 bolt into motor oil the dry torque of 78 ft lbs should be reduced to about 55 ft lbs. If you use graphite/oil the figure should be reduced to 42 ft. lbs. Note this chart is for Grade 8 fasteners. People are usually concerned about spark plugs into aluminum heads. The plugs are often plated. A dab of motor oil and 15 ft lbs should be reduced to 10-11 ft lbs. If you dont' have a starting point on your fastener read the head marking in the diameter you have and put the these tables on your shop wall (Hot Rod Magazine 1970's). PS 12-27, The authors mentioned that lock tite has very little effect on torque.
Attachments
#2
S
SeniorCitizen
S
SeniorCitizen
QUOTE If you don't have a starting point on your fastener read the head marking .
**************************************************************
If both components aren't of the same grade I would think that point would be moot .
Mine will get lubricant every time and the lesser value. I just don't care for thread galling .:biggrin:
Some interesting facts in this link even though they are for stainless.
http://www.estainlesssteel.com/gallingofstainless.html
**************************************************************
If both components aren't of the same grade I would think that point would be moot .
Mine will get lubricant every time and the lesser value. I just don't care for thread galling .:biggrin:
Some interesting facts in this link even though they are for stainless.
http://www.estainlesssteel.com/gallingofstainless.html
#3
M
motoman
What was meant: If the grade (hardness ) is unknow then the dry torque starting point is unknown. I would start with grade 5 or 6. If one assumes the female or nut is an 8 and applies high torque that would probably not be good for a grade 6 thread , no? I realize earlier talk on the forum has stated grade 8 used on blades. My craftsman seems more like a 5 or 6 based on manual callout of 45-55 ft lbs (dry).
Anyway ,identify (or assume) the grade , look up the torque on a chart. If you must lubricate, the charts above should help.
Craftsman blade bolts have held up well with removals about 2-3 times per summer for sharpenng, wiped clean and dry. Although the heads and washers look a little rusty they clean up easily . Once loosened, finger removal. The threads are not rusty so the washer seat in the blade and the bolt head on the washer hole is effective in keeping water out of thread area. Curiosity , my bolt heads are stamped with alpha-numeric gibberish I cannot decode (not metric). Probably proprietary factory marking.
M
motoman
QUOTE If you don't have a starting point on your fastener read the head marking .
**************************************************************
If both components aren't of the same grade I would think that point would be moot .
Mine will get lubricant every time and the lesser value. I just don't care for thread galling .:biggrin:
Some interesting facts in this link even though they are for stainless.
Stainless Steel Galling / Locking Up / Freezing Up
What was meant: If the grade (hardness ) is unknow then the dry torque starting point is unknown. I would start with grade 5 or 6. If one assumes the female or nut is an 8 and applies high torque that would probably not be good for a grade 6 thread , no? I realize earlier talk on the forum has stated grade 8 used on blades. My craftsman seems more like a 5 or 6 based on manual callout of 45-55 ft lbs (dry).
Anyway ,identify (or assume) the grade , look up the torque on a chart. If you must lubricate, the charts above should help.
Craftsman blade bolts have held up well with removals about 2-3 times per summer for sharpenng, wiped clean and dry. Although the heads and washers look a little rusty they clean up easily . Once loosened, finger removal. The threads are not rusty so the washer seat in the blade and the bolt head on the washer hole is effective in keeping water out of thread area. Curiosity , my bolt heads are stamped with alpha-numeric gibberish I cannot decode (not metric). Probably proprietary factory marking.
#4
E
Elias40
E
Elias40
Thanks Motoman for sharing this very important information with us. We have always cleaned: and oiled, depending on the fastener type, and it's duty, but never paid much attention to what different lubricants would do with torque specifications.
#5
E
Elias40
Grade 8 used on blades- there is a brittleness factor to be concerned with as well. If you do hit something, there would absolutely be no flex in the bolt material, and it would snap.
E
Elias40
What was meant: If the grade (hardness ) is unknow then the dry torque starting point is unknown. I would start with grade 5 or 6. If one assumes the female or nut is an 8 and applies high torque that would probably not be good for a grade 6 thread , no? I realize earlier talk on the forum has stated grade 8 used on blades. My craftsman seems more like a 5 or 6 based on manual callout of 45-55 ft lbs (dry).
Anyway ,identify (or assume) the grade , look up the torque on a chart. If you must lubricate, the charts above should help.
Craftsman blade bolts have held up well with removals about 2-3 times per summer for sharpenng, wiped clean and dry. Although the heads and washers look a little rusty they clean up easily . Once loosened, finger removal. The threads are not rusty so the washer seat in the blade and the bolt head on the washer hole is effective in keeping water out of thread area. Curiosity , my bolt heads are stamped with alpha-numeric gibberish I cannot decode (not metric). Probably proprietary factory marking.
I realize earlier talk on the forum has stated grade 8 used on blades. My craftsman seems more like a 5 or 6 based on manual callout of 45-55 ft lbs (dry).
Grade 8 used on blades- there is a brittleness factor to be concerned with as well. If you do hit something, there would absolutely be no flex in the bolt material, and it would snap.
#6
M
motoman
Not so sure of that Mr Elias. Brittleness is tempered out. Grade 8 is widely used in race applications and one gentleman on this forum was surprised I once mentioned grade 5/6 as he had not seen them in south. Usually grade 6 is bagged and sold in auto stores (three slashers). Also I think in open stock in H Depot and in the specialty drawers at Lowes. We all know to avoid plain, unmarked commercial grade bolts for blade retention, I hope.
Even though many are now saying "motoman, STFU!" I now think about a lot of archived material on metric, but you will really have to convince me you need it.
M
motoman
Grade 8 used on blades- there is a brittleness factor to be concerned with as well. If you do hit something, there would absolutely be no flex in the bolt material, and it would snap.
Not so sure of that Mr Elias. Brittleness is tempered out. Grade 8 is widely used in race applications and one gentleman on this forum was surprised I once mentioned grade 5/6 as he had not seen them in south. Usually grade 6 is bagged and sold in auto stores (three slashers). Also I think in open stock in H Depot and in the specialty drawers at Lowes. We all know to avoid plain, unmarked commercial grade bolts for blade retention, I hope.
Even though many are now saying "motoman, STFU!" I now think about a lot of archived material on metric, but you will really have to convince me you need it.
#7
E
Elias40
The '70s F subframe used by General Motors; Used 4 grade 8 bolts attaching the subframe to the body. They had a problem with the bolts snapping off from a 30mph front end collision, causing the front of the car to fold in, crushing the driver. Inspectors stated, that because of the bolts used, it created a weak assembly, that would otherwise be an easy to survive fender bender.
Just an example
E
Elias40
Not so sure of that Mr Elias. Brittleness is tempered out. Grade 8 is widely used in race applications and one gentleman on this forum was surprised I once mentioned grade 5/6 as he had not seen them in south. Usually grade 6 is bagged and sold in auto stores (three slashers). Also I think in open stock in H Depot and in the specialty drawers at Lowes. We all know to avoid plain, unmarked commercial grade bolts for blade retention, I hope.
Even though many are now saying "motoman, STFU!" I now think about a lot of archived material on metric, but you will really have to convince me you need it.
The '70s F subframe used by General Motors; Used 4 grade 8 bolts attaching the subframe to the body. They had a problem with the bolts snapping off from a 30mph front end collision, causing the front of the car to fold in, crushing the driver. Inspectors stated, that because of the bolts used, it created a weak assembly, that would otherwise be an easy to survive fender bender.
Just an example
#8
M
motoman
M
motoman
I cannot comment further. Beyond my knowledge, but IMO its hard to understand how many on this forum have stated they have grade 8 bolts holding their blades on, without stories of catastrophe since the buggers are exposed to rocks, pipes, boulders, concrete abutments and the like. Rivets or Il Engine or Chance or others chime in please . :anyoneThe '70s F subframe used by General Motors; Used 4 grade 8 bolts attaching the subframe to the body. They had a problem with the bolts snapping off from a 30mph front end collision, causing the front of the car to fold in, crushing the driver. Inspectors stated, that because of the bolts used, it created a weak assembly, that would otherwise be an easy to survive fender bender.
Just an example
#9
R
Rivets
R
Rivets
Interesting thread. You've made me go back to my machinist training. First two websites will give you a basic understanding of bolt grading for the average engineer and consumer. These grades are standardized by the SAE (Society of Automotive Engineers). They are the most commonly used in the automotive and small engine industry. The last site shows a much more comprehensive chart and breaks the relatively SAE standards into a more precise and tighter ISO ( International Organization for Standards) standards.
You will see that there is no grade 6 bolt in the SAE standards and I assume that the bolts you are talking about (3marks) are grade 5. Don't really know about the grade of blade nuts, but in my opinion anything higher than grade 8, for this application, would overkill and possibly to brittle.
Bolt Depot - Bolt Grade Markings and Strength Chart
SAE Grades Steel Bolts
American Fastener - ASTM, SAE, and ISO Grade Markings
You will see that there is no grade 6 bolt in the SAE standards and I assume that the bolts you are talking about (3marks) are grade 5. Don't really know about the grade of blade nuts, but in my opinion anything higher than grade 8, for this application, would overkill and possibly to brittle.
Bolt Depot - Bolt Grade Markings and Strength Chart
SAE Grades Steel Bolts
American Fastener - ASTM, SAE, and ISO Grade Markings
#10
S
soulman
S
soulman
Having spent 32 years in quality assurance for a major tractor mfg. I have never heard of a grade 6 bolt.
#11
E
Elias40
E
Elias40
STFU? No, not in the least. You have the same right to bark as anyone else here. Take it from RED//GREEN We're all in this together. We can't possibly be right on everything. We went to a trade school; and one of the things stressed is that the 3 marks for 5 grade, or 6 grade, if you want, & 5 marks for 8 grade Coming from the groovy SAE boneheads, was to keep everybody, engineers included, in a deep state of confusion.Not so sure of that Mr Elias. Brittleness is tempered out. Grade 8 is widely used in race applications and one gentleman on this forum was surprised I once mentioned grade 5/6 as he had not seen them in south. Usually grade 6 is bagged and sold in auto stores (three slashers). Also I think in open stock in H Depot and in the specialty drawers at Lowes. We all know to avoid plain, unmarked commercial grade bolts for blade retention, I hope.
Even though many are now saying "motoman, STFU!" I now think about a lot of archived material on metric, but you will really have to convince me you need it.
#12
E
Elias40
E
Elias40
See, if we get input from those with enough sperience, thousand years or so, we might eventually be able to hit the target, even though the arrow is crooked, with target missing it's eye.Having spent 32 years in quality assurance for a major tractor mfg. I have never heard of a grade 6 bolt.
#13
E
Elias40
But, if the blades were installed en mass, They would use self-tapping 8 grade bolts, especially self locking, Driven by an air tool at it's maximum rated input 90psi, or so, They would tear everything up on the way in, and lock down tight. It may be the reason why we can't remove the bolts, as they sort become fused inside their nest.
E
Elias40
Interesting thread. You've made me go back to my machinist training. First two websites will give you a basic understanding of bolt grading for the average engineer and consumer. These grades are standardized by the SAE (Society of Automotive Engineers). They are the most commonly used in the automotive and small engine industry. The last site shows a much more comprehensive chart and breaks the relatively SAE standards into a more precise and tighter ISO ( International Organization for Standards) standards.
You will see that there is no grade 6 bolt in the SAE standards and I assume that the bolts you are talking about (3marks) are grade 5. Don't really know about the grade of blade nuts, but in my opinion anything higher than grade 8, for this application, would overkill and possibly to brittle.
Bolt Depot - Bolt Grade Markings and Strength Chart
SAE Grades Steel Bolts
American Fastener - ASTM, SAE, and ISO Grade Markings
But, if the blades were installed en mass, They would use self-tapping 8 grade bolts, especially self locking, Driven by an air tool at it's maximum rated input 90psi, or so, They would tear everything up on the way in, and lock down tight. It may be the reason why we can't remove the bolts, as they sort become fused inside their nest.
#14
M
motoman
M
motoman
Well since I have permission to keep babbling...I am at a disadvantage since my tractor pool is 1 (as in one). But the cub cadet nuts mentioned recently are puzzling . These are about the size of my Intek flywheel nut.? Why would a mfgr do that to a struggling homeowner ? And held in place by clamping? Maybe I should relent and praise MTD -Craftsman for the easy and reliable blade set up I have. This praise could undo a milligram's worth of frustration with the Intek. OK , craftsman,I praise you. :laughing:
#15
M
motoman
Self tapping grade 8...we could get Hercules to turn the lever arm.
M
motoman
But, if the blades were installed en mass, They would use self-tapping 8 grade bolts, especially self locking, Driven by an air tool at it's maximum rated input 90psi, or so, They would tear everything up on the way in, and lock down tight. It may be the reason why we can't remove the bolts, as they sort become fused inside their nest.
Self tapping grade 8...we could get Hercules to turn the lever arm.
#16
M
motoman
I'm glad you did not mention a high count quiver magazine. Don't go there.:thumbdown:
M
motoman
See, if we get input from those with enough sperience, thousand years or so, we might eventually be able to hit the target, even though the arrow is crooked, with target missing it's eye.
I'm glad you did not mention a high count quiver magazine. Don't go there.:thumbdown:
#17
M
motoman
M
motoman
OK soulman, it seems I'm being over ruled. Where, oh where ,could I have got that one? Maybe an even number crept into my noggin , somehow. ThanksHaving spent 32 years in quality assurance for a major tractor mfg. I have never heard of a grade 6 bolt.
#18
M
motoman
Thanks, sandbur. Good thread. Machining stainless is a bummer . A lot of carbide cutters used.
M
motoman
QUOTE If you don't have a starting point on your fastener read the head marking .
**************************************************************
If both components aren't of the same grade I would think that point would be moot .
Mine will get lubricant every time and the lesser value. I just don't care for thread galling .:biggrin:
Some interesting facts in this link even though they are for stainless.
Stainless Steel Galling / Locking Up / Freezing Up
Thanks, sandbur. Good thread. Machining stainless is a bummer . A lot of carbide cutters used.
#19
M
motoman
My grade 6 bolt nightmare...am I losing it? Finally called Judge Judy who said "Never give up your dream...even if over ruled. " So ...see chart below. Last 2 sentences of text are what Elias told us.
M
motoman
Having spent 32 years in quality assurance for a major tractor mfg. I have never heard of a grade 6 bolt.
My grade 6 bolt nightmare...am I losing it? Finally called Judge Judy who said "Never give up your dream...even if over ruled. " So ...see chart below. Last 2 sentences of text are what Elias told us.
Attachments
#20
M
motoman
Well since talking to Judge Judy and finding grade 6 really lives I must remain humble and correct the bagged- tagged remark. Three slashers grade 5, FOUR slashers=grade 6 which I never see either, but they live.
M
motoman
Not so sure of that Mr Elias. Brittleness is tempered out. Grade 8 is widely used in race applications and one gentleman on this forum was surprised I once mentioned grade 5/6 as he had not seen them in south. Usually grade 6 is bagged and sold in auto stores (three slashers). Also I think in open stock in H Depot and in the specialty drawers at Lowes. We all know to avoid plain, unmarked commercial grade bolts for blade retention, I hope.
Even though many are now saying "motoman, STFU!" I now think about a lot of archived material on metric, but you will really have to convince me you need it.
Well since talking to Judge Judy and finding grade 6 really lives I must remain humble and correct the bagged- tagged remark. Three slashers grade 5, FOUR slashers=grade 6 which I never see either, but they live.
#21
C
chance123
C
chance123
While we are on the subject of bolts, You can't imagine how confused I got many years ago when I ran across some bolts on a British motorcycle with "witworth" threads! Sheesh! LOL
#22
pugaltitude
Oh the joys of witworth.
Wasnt that long ago when they finally stopped putting in witworth sockets into full sets.
Metric or imperial would not fit witworth. A league of their own!!!! :laughing:
pugaltitude
While we are on the subject of bolts, You can't imagine how confused I got many years ago when I ran across some bolts on a British motorcycle with "witworth" threads! Sheesh! LOL
Oh the joys of witworth.
Wasnt that long ago when they finally stopped putting in witworth sockets into full sets.
Metric or imperial would not fit witworth. A league of their own!!!! :laughing:
#23
E
Elias40
E
Elias40
IGNORE/NO COMMENTIf you are concerned about corrosion and removal of a bolt or nut, you may have cleaned,lubricated and then torqued the fastener as usual , maybe by the torque settting in the owner's or workshop manual. Welcome to the world of limited information.
Almost all torque callouts are for dry , clean threads. When you lubricate and tighten to your favorite torque you are probably over -tightening by up to 45% (yes forty-five percent). This stresses the fastener toward its elastic limit where it looses clamping ability, necks down, work hardens and distorts threads. Sometimes you can see this with the naked eye. Do not reuse over- torqued fasteners
In this forum the most obvious fasteners subject to concern must be blade bolts and nuts. They are usually corroded or rusty on the outside and hard to get off , especially if not frequently removed.
Look at the charts below carefully . If you dip that clean dry 7/16 " x 20 bolt into motor oil the dry torque of 78 ft lbs should be reduced to about 55 ft lbs. If you use graphite/oil the figure should be reduced to 42 ft. lbs. Note this chart is for Grade 8 fasteners. People are usually concerned about spark plugs into aluminum heads. The plugs are often plated. A dab of motor oil and 15 ft lbs should be reduced to 10-11 ft lbs. If you dont' have a starting point on your fastener read the head marking in the diameter you have and put the these tables on your shop wall (Hot Rod Magazine 1970's). PS 12-27, The authors mentioned that lock tite has very little effect on torque.