Torque wrench needed, reasonable suggestions?

[denbsteph]

Threads, pitch change, stretching threads, torque fasteners? WTF?? I'm a simpleton, I do not possess a engineering degree, nor am I mechanically inclined, please continue on with the wonderful "Torque Wrench" lecture. Torque Wrench's..... high tech ****! Stole that line and twisted it a bit from the master "George Carlin "

 

[whenfoxforks-ruled]

Threads are measured in threads per inch, or threads per mm, or what ever the French use. A different amount of threads per inch, has a different pitch/angle. When abused, you should be able to see the angle change, right where the nut seats at. If it was 10 threads per 10 mm for example, it will still have that amount under the nut, but in changes angle where it gets torqued at, the thread gets stretched/pulled stripped. I have some fleabay parts, head and cylinder. Right above or below, where the head nuts normally go, you can see a different angle on the studs. This top end was a hopeless head gasket leaker. Even using the torque wrench, would not help, at this point. The studs and nuts need to get replaced, the head and top of cylinder are waiting to get resurfaced. The pinch bolts on the fork clamps. Too tight will seize the parts inside from sliding up and down smoothly. Too loose and the front wheel will twist in odd directions upon impact. Properly torqued, no issues, unless the threads have issues. Stripping 4 mm aluminum threads can be stopped, after you make sure the threads are good to begin with! Otherwise, that torque wrench is just a dandy leverage bar? Sometimes a weapon.

 

[mudpack]

If threads have been deformed enough for you to visually detect it, they will no longer accept full tightning torque. Since they will no longer perform the task for which they were designed, i.e.will not carry full design loads, they are of no use.
One might describe them as "stretched", but to me stretched implies "still somewhat useable". I do not consider a fastener that will no longer carry its design load as useable, so I prefer the term "pulled", which implies that they need to be "replaced before use".
I suppose on paper it's all semantics.
Bottom line: use an accurate torque wrench. If the fastener won't accept full prescribed torque, replace the component(s) that have damaged threads.
I hope we haven't made this appear to be more complex than it really is.

 

[mudpack]

The pinch bolts on the fork clamps. Too tight will seize the parts inside from sliding up and down smoothly.

You sure about that?

 

[Rich Rohrich]

Actually, threads don't stretch, they pull.

Actually... ;) ( I know mudpack is an engineer, so this is just general info to add to the thread, not directed at him. He has probably forgotten more about the subject than I know)


... all bolts and studs (regardless of material makeup) are slightly elastic and must be stretched a small amount to develop clamping force.

A common engineering rule of thumb is a stretch of .001 inch per inch length of a fastener develops about 30,000 psi clamping force in steel.

When you under torque something there isn't any stretch in the fastener and the clamping force will be inadequate. If you over-torque a bolt or stud it can be stretched beyond it's elastic limit and the "springiness" that provides the clamping force will be lost and the part will fail.

Measuring the bolt length difference (or stretch) from an unloaded state to a loaded state is the standard way to "torque" connecting rod caps in high performance plain bearing engines

Along with the clamping force you apply fasteners constantly stretch and return to their original shape in the course of holding together the parts. A fastener that has gone past it's elastic limit will not be able to function in this stretch -return cycle and will usually fail.

There are a limit to the number of stretch return cycles a fastener can handle, but for non-critical bolts with proper torque most of us will never reach the fatigue limit of a good quality bolt. That chinese junk they sell at Home Depot is another matter entirely ;)

There are lots of other things involved with this but probably the most important for our purposes is the influence that lubrication on the bolt plays in the final torque reading.

Overcoming the fastener friction accounts for a major portion of the torque required to turn a fastener. A dry bolt might obtain the same torque reading as a properly lubed one, but the clamping force applied will be much higher on the lubed bolt because more of the applied torque will be converted into useable clamping force.

The OEM's base their torque specs on a torque readings obtained by a low friction lubed connection, so if you plan to use a torque wrench, you need to break out the moly based assembly lube as well.

There is an old motorcycle adage that has served me well over the years.
Every bolt needs lube or loctite. Nothing goes together dry.

As mudpack pointed out, the root interface for studs or bolts when a steel fastener is threaded into aluminum is also a common point of friction and subsequently becomes a common cause of failure. The fastener can't stretch and apply clamping force if the aluminum threads (the root interface) can't support the load. You need enough contact area between the steel fastener and the aluminum threads to provide the clamping force. Having a good set of metric bottoming taps around to maintain aluminum threads can make all the difference over time.

If you measure a few bolts the next time you are working on your bike you'll find the Japanese are very disciplined about following the engineering standard of providing a minimum threaded depth into aluminum of two times the diameter of the bolt.

Drop a bolt in a side case hole and measure the distance from the bottom of the bolt head to the case and you'll see what I mean. This is a standard trick to figure out where a bolt goes if you are not sure. Drop it in the hole and if it doesn't stick out 2xdiameter then it's not the right one.

To sum it up :
- Use clean high quality bolts
- Use moly based lube on the bolts
- use an accurate torque wrench within it's usable range
- DON'T OVER TORQUE

 

[Joburble]

... so if you plan to use a torque wrench, you need to break out the moly based assembly lube as well.

:cool: and don't put too much lube in the hole or the bolt may hydraulic and you will get a false torque reading. Just lightly lube the bolt threads.

Based on personal experience when I was a "know it all" teenager. "Why is all the water pissing out from under the head, I torqued all the bolts up good?" Doh!

 

[Rich Rohrich]

:cool: and don't put too much lube in the hole or the bolt may hydraulic and you will get a false torque reading. Just lightly lube the bolt threads.

Good point! :cool:

 

[whenfoxforks-ruled]

You sure about that?

The triple clamps to forks needs to be cleaned of flashing, and put together dry. Proper torque is very important on the clamps. Too tight will squeeze the inside of the upper fork leg, and impair the slider from going up and down. Conventional forks, I have forgot about already? I am no engineer, but I hopped a train once. The lube or lock tight slows corrosion also. Well it sure makes taking apart more fun than replacing half the bikes fasteners, due to be seized. The cheap alternatives? Some can not even lube or use the correct fasteners. Expert restoration process my eye, with hardware store nuts and bolts? Oh boy! Its always the little things. I would have forgot about all the stripped and abused parts, if it was not for this recent build a bike from fleabay cheap idea, and the parts from perfect running bikes, sorry. But something so trivial could be, and is over looked way too much. If people quit buying and using junk, wouldn't they quit selling it? Vintage Bob

 

[denbsteph]

I have to tell you, the past several post's have taken this thread to a different level, a level I was unaware about.

In a nut shell so far, never torque dry nuts, use a lube such as loctite, moly lube. Got that part down.

Rich: Are you a writer? Reason for the comment, you painted a picture that I understood. It makes sense, Thanks!!

Back to torque wrench's. In other words, drop some duckies on a well made wrench, perhaps one made in the USA. Leave the Chinese, Taiwanese junk alone, so to speak.

What type? Beam or Clicker? Will the beam wrench do the job that is required, but not stress the bolts but create enough of the elastic stretch to produce the clamping effect that is needed? I think that is what Rich said in a nutshell. Thanks!!

 

[mudpack]

I fully agree with most of what Rich said. One part I disagree with is putting fasteners together with lube. Most service manuals that give a torque value for a particular fastener give that value for dry, clean threads.
For example, this is what my GM factory service manual says about it:
"UNLESS OTHERWISE SPECIFIED, do not use supplemental coatings (such as paints, greases, or other corrosion inhibitors) on theaded fasteners or fastener joint infterfaces. Generally, such coatings adversely affect the fastener torque and the joint clamping force, and may damage the fastener."
I have a Haynes manual which says "torque values given are for dry threads".
My Bently manual also gives the same cautions.

Unless the manual specifically calls for a particular lube on the threads (and I have seen them do exactly this in specific instances), do not use it. It will throw off the torque values, as Rich said.

 

[Rich Rohrich]

Most service manuals that give a torque value for a particular fastener give that value for dry, clean threads.

I'm not sure what they put in a KDX manual on this subject because the truth is I've never seen one , but flipping through a current Honda service manual it's tough to find a critical bolt that doesn't have a call out for lube or a locking agent as part of the torque spec.

Following what the OEM service manual calls for is certainly a logical and safe approach to these issues. Knowing a little something about how Haynes and Clymer type manuals are put together I'd put them in the same category as the Chinese torque wrenches. They are great for starting a local landfill, but their value quickly diminishes past that point. People would be well served to buy a proper Factory Service Manual. The little bit extra it costs over the publishing company versions will prove to be money well spent for most.

Beyond what is written in the service manual, adding in some knowledge of what you are trying to accomplish along with a healthy dose of common sense should cover any of the grey areas that pop up in the imperfect world of mechanical things that actually get used.

The best advice I can give is don't take my word for it, instead understand how these things work, so you can make your own informed decision.

With that in mind, for anyone who wants to know more about this stuff, engineering texts have tons of useful info but they can be rough sledding when you want answers to more real world type questions. For those types of answers, the best book I've found on the subject is Carroll Smith's "Nuts, Bolts, Fasteners and Plumbing Handbook". It was written by a real practicing race engineer, who just happens to be a damn good writer. It's an enormously readable and useful book for under $20.

While your at it, buy his book "Engineer To Win" as well. l guarantee these two books pack more useful info per page than 20 years worth of magazines subscriptions. :cool:

 

[mudpack]

KDX200 Motorcycle Service Manual, P/N 99924-1181-10, General Information, Torque and Locking Agent, page 1-11 says this:
"All of the (torque) values are for use with dry, solvent-cleaned threads."
My Honda Service Manual for the CRF150R has several pages of torque values for the machine. In the notes section of some of those values it says, "Apply engine oil to the threads and seating surface." It actually gives this instruction on a significant number of fasteners, all of which seem to be internal to the engine. All the rest of the values do not say this, which means "do NOT apply engine oil to the fastener"..... :nod: This is always the default condition.

I stand by my previous statement that unless the manual specifically states to use lube or locker on a fastener's threads, the torque values are for clean, dry threads. It's safest, by far, to assemble dry than to assemble with oil, for the very reasons Rich stated earlier.

By the way, I just looked at my copy of Carrol Smith's "Tune to Win". Good stuff, but doesn't tell us anything about lubing or not lubing our fasteners. :cool:
Rich, what does he say in his "Engineering to Win" about lubing fasteners prior to torquing??? My copy of that book is at my youngest son's place, which is 1500 miles away...

 

[ellandoh]

What About Anti-Sieze?? 

 

[mudpack]

What About Anti-Sieze?? 

I would use anti-sieze in two instances:
1. If the manual calls for it in that application.
2. If you have been experiencing galling on that particular fastener. This usually means using it on fasteners that are subject to extreme heat, such as header/exhaust manifold nuts or bolts.
If you decide to use anti-seize on a fastener that doesn't call for it explicitly, then I'd reduce the torque value for that fastener about 20%.

Anti-sieze is a mixture of oil and finely-powdered metals, such as lead and copper, sometimes silver in small amounts. As far as how it affects torque values, just treat it like you would any other lubricant, i.e. with caution.

 

[mudpack]

The best advice I can give is don't take my word for it,

That is excellent advice, Rich, and I hope my KDX200 brothers here will apply that to what I write as well.
Rich has written some intelligent stuff, and his remark about going by the manuals cannot be disputed.


NOTE: if the manual we are reading tells us to do something that "common sense" might indicate is wrong, the odds favor us if we choose to go by the manual. :nod: Sometimes that which seems logical to us is not the complete truth.

 

[mudpack]

A common engineering rule of thumb is a stretch of .001 inch per inch length of a fastener develops about 30,000 psi clamping force in steel.

The clamping force of a threaded fastener is not one value for all fasteners. Clamping force per thousandths of an inch stretch varies according to:
A) Fastener length (from under the head to the last free thread).
B) Fastener diameter.
C) Fastener tensile strength, including material and heat treatment.

E.g. torquing a 3" long 4-40 bolt to 0.001" stretch gives less clamping force than torquing a 1" long 1/2"x13 bolt to 0.001" stretch, by several orders of magnitude.

 

[Rich Rohrich]

The clamping force of a threaded fastener is not just one value. Clamping force per thousandths of an inch stretch varies according to:
A) Fastener length (from under the head to the last free thread).
B) Fastener diameter.
C) Fastener tensile strength, including material and heat treatment.

The POINT of that post was to show that a relationship between fastener stretch and clamping force exists, and that there is an elastic limit to even something as tough as a steel bolt. My intention was not to teach Engineering 101.

Your earlier post...

Actually, threads don't stretch, they pull. If you can't apply full torque on a fastener, the threads are pulled.

... seemed to (in my estimation) confuse this some. It appears you have taken my responses to all this as some sort of personal slight inspite of my best efforts to the contrary. I can see where this is going so I'll save you lots of ASCII, and step aside now.

If people are unclear about the things I posted they would be well served to read the reference I posted and use common sense so they can make an informed decision on their own.

Blind faith in anyone, or anything (the OEM service manuals included ) rarely proves to be a fruitful endeavor.

 

[denbsteph]

In my opinion I believe those that have chimed in have opened my eyes to the stretch of threads, their limits as far as what type of torque can be enforced/introduced on them. The cheap Chinese metals that are being flooded into this market, the strict and meticulous ways of the Japanese etc, etc,etc.

I'm not a motor head nor do I hold an Engineering degree, but I have learned something from ALL the individuals who have posted here. We all take what we want to read/hear, run it through our brains and decide if it is good enough, if it is, we keep it retained until that day it is needed to be brought out. If we don't want it then we spit it out and let it be on its merry way for someone else to use.

I will say, every time I read the service manual yesterday on the KDX, I seen VERY few instances were any type of "Loctite" was recommended. So I did what the manual said, no loctite, it did not get it. If it said coat with 2 stroke oil I did.

Any who, I received valuable info from EVERYONE, even though the thread did get
"hi jacked ", LOL!!! I did eventually get a Torque wrench, I spoke to a motor head who works at a local Toyota shop, he stated use common sense when using it, wind it down when done with it and get one I feel will do the job, most of all take care of it don't drop it, don't use it as a breaker bar. Thanks again,Dennis

 

[mudpack]

.... a relationship between fastener stretch and clamping force exists, and that there is an elastic limit to even something as tough as a steel bolt.

Indeed it does, and indeed there is, Rich.

I haven't taken your responses as any sort of personal attack, Rich, and hope you aren't taking mine as such.
I would have pointed out the error no matter who had posted it.
You've been quite civil when we've disagreed during the discussions and have brought up some very valid points. I have found it easy to respond in kind. Bringing common errors to light is not intended to be any sort of attack, and if it seemed that way to you, I certainly am sorry. Peace?

Sounds like your friend gave you some good advice, Dennis. :cool:

 

[whenfoxforks-ruled]

There is no way, that my dirt bike will ever be getting a saw, torch or jack hammer to get bolts out again. I care, sorry. Or, can you show me how or where it causes more harm than good? Except greasing up the throttle tube! And there is electrolysis from dissimilar metals? Too bad, and replace the fasteners as needed? I am pretty sure that I could never keep my van as workable as my dirtbike. I would need more people, and more money. But, it would be nice for parts to come off when I want them to! Vintage Bob

 

[Rich Rohrich]

Indeed it does, and indeed there is, Rich.

I haven't taken your responses as any sort of personal attack, Rich, and hope you aren't taking mine as such.
I would have pointed out the error no matter who had posted it.

That works for me! :cool: