The effect of lubricant on Torque tightening. If there is the presence of a lubricant on a fastener, the coefficient of friction on the thread and the under-head changes. When a fastening is then Torqued up, it is overcoming the friction and applying a clamp load. If the friction goes down due to a lubricant then the clamp load will alter for the same Torque applied.
How does lubricant affect tightening torque?
What went unexplored until recently was how lubricant affects the Nut Factor on a fastener, which then affects tightening torque, and therefore effects the bolt tension. But that’s just the beginning. Through years of research and first-hand experience, we have found that many lube manufacturers don’t know how their lube performs in the field.
What is the torque of a lubricated bolt?
When a bolt is lubricated - less torque is required to achieve bolt axial load or tension. Reduction of torques for lubricated vs. dry bolts are indicated in the table below. The maximum tightening torque for a slightly lubricated 1" Grade 5 coarse bolt is 483 lb ft.
What are the benefits of lubricants?
• Lubricants ease the amount of torque required to get the bolt properly tight, so you use your energy more efficiently. • Lubricants provide better wear resistance, allowing surfaces to slide smoothly across each other—especially important for some materials like stainless steel, which tend to cold-weld, causing galling and embedment.
How much does lubricant affect bolt stress?
In the second test, by using lubricant the average bolt stress increased by 5.4 Ksi, but still came up short of our target of 40 Ksi. Bolts that are not lubricated in the same fashion will have a greater variation in the bolt load.
Why don't you use thread lubricant?
Why is torque used as an indicator?
What is the force that pulls a bolt back?
What is lubricant made of?
Is torque always tight?
Is torque a measure of tightness?
See 1 more
How does lubrication affect the preload and torque of bolts?
Dry bolt torque is approximately 30% higher - or 628 lbf ft. If the bolt is lubricated with SAE 30 oil - the torque compared to a dry bolt is reduced with approximately 40%. Note that if torque specified for a dry or slightly oiled bolt torque is applied to a lubricated bolt - the bolt may overload and break.
Do lubricants have an effect on the relationship between torque and clamping force?
When a fastening is then Torqued up, it is overcoming the friction and applying a clamp load. If the friction goes down due to a lubricant then the clamp load will alter for the same Torque applied.
Does Antiseize affect torque?
When applying an anti-seize to your components, the torque value to achieve the same clamp load will be lower. If anti-seize is used with the torque specified for a dry assembly, you risk exceeding the proof load of the fastener.
What is the effect of lubricants on friction?
It has been shown that friction could both increase or decrease with lubrication, depending upon the nature of the application. In tests on straight sutures, lubricants have generally led to an increase in friction.
When should you lubricate a bolt?
When tightening a fastener ALWAYS use a controlled method. Unless specifically told not to, always lubricate the fastener.
How do you use lubricant on bolts?
Castrol Stick Wax For best results, apply wax as a couple stripes along the threads where the nut will thread onto the bolt. Approximately 50% of input torque is consumed where the threads of the nut and bolt meet. Next, swipe the washer face of the nut, with the wax, where it will contact the flat washer.
Will grease work as anti-seize?
Designed to convert torque to tightening force more efficiently, anti-seize is formulated with high solids content and a carrier grease....Anti-Seize.GreaseAnti-SeizeTypically not suitable for temperatures above 400°FSuitable for high temperature environments2 more rows•May 1, 2020
Does anti-seize cause bolts to loosen?
Anti-seize lubricants shouldn't cause bolts to loosen. However, it shouldn't be applied on torque-rated fasteners without accounting for the loss of torque.
Can anti-seize be used as a lubricant?
Anti-seize products are applied to bolts, fasteners, flanges and other clamped interfaces to prevent galling, seizing and corrosion, as well as lubricating to ease disassembly.
How does lubricant decrease frictional force?
When lubricant is applied between the moving parts of a machine, a thin layer is formed there and moving surfaces do not directly rub against each other. Interlocking of irregularities is avoided to a great extent and movement becomes smooth. Thus friction is reduced.
Why does oil decrease friction?
When oil is applied between the two surfaces in contact, a thin layer of oil is formed between the two surfaces. This layer separates the two surfaces a little bit due to which their interlocking is reduced to a large extent when they rub against each other.
How does a lubricant work?
Lubricants aim at reducing friction between moving pieces and at reducing passive resistance of the stationary parts. They are produced by refining heavy fractions of crude oil (remaining crude oil parts after refining hydrocarbons such as gas, fuel oil or kerosene).
When should you not use anti-seize?
Anti-seize can not be applied on already damaged or cross threaded threads of bolts. The threads need to be chased, re-tapped or repaired before applying anti-seize. Don't use anti-seize on exposed threads as it may attracts contaminates that may contribute to thread damage.
Should I put anti-seize on lug nuts?
But experts tell us not to use any lubricant, including anti-seize compound, on wheel studs or nuts. The tech folks at Tire Rack state: "Torque specifications are for dry threads only. The fastener threads should be free of oil, dirt, grit, corrosion, etc. It is important NOT to lubricate hardware threads or seats.
How much torque can aluminum threads take?
Sprocket Nut Safety: Aluminium Sprocket Nuts are manufactured to allow a torque of 33 ft/lbs or 44Nm. When fitting, wrap with a thin, tough tape such as Teflon to prevent scratching.
How long will anti-seize last?
The shelf life is important. If stored correctly, an anti-seize compound should retain its performance in key operations e.g. coefficient of friction in fastener tightening. The majority of products have a 5-year shelf life from the date of manufacture.
Torque specs-dry vs oil - Mechanical engineering general discussion ...
I have CAT-50 tool holders that have a 1 -8 thread pull stud with a 110 ft.lbs. max. torque spec. This seems quite sufficient if the threads were always dry. Ho
Reduced Torque with Lubricated Bolts - Engineering ToolBox
Example - Reduction of Torque when Bolt is Lubricated. The maximum tightening torque for a slightly lubricated 1" Grade 5 coarse bolt is 483 lb f ft.Dry bolt torque is approximately 30% higher - or 628 lb f ft.. T dry = (483 lb f ft) (1 + (30%) / (100%)) = 628 lb f ft If the bolt is lubricated with SAE 30 oil - the torque compared to a dry bolt is reduced with approximately 40%.
clamping force, bolt torque dry vs. lubricated - Bus Conversion Magazine
Nice post Kyle. In another life, on a planet far away, I worked as a Maintenance Engineer in a Nuke Power Plant. I worked on the big valves. We were real interested in them not leaking when we put them back together.
Lubrication effect on bolt tension and torque
When a bolt is lubricated - less torque is required to achieve bolt axial load or tension. Reduction of torques for lubricated vs. dry bolts are indicated in the table below.
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Citation
Engineering ToolBox, (2010). Reduced Torque with Lubricated Bolts. [online] Available at: https://www.engineeringtoolbox.com/torque-lubrication-effects-d_1693.html [Accessed Day Mo. Year].
What happens if you don't apply lubricant properly?
If that lubricant isn’t applied generously/properly, the dry parts of the fastener will increase your Nut Factor and result in different bolt loads on each of your fasteners.
What is proper bolt lubrication?
Proper bolt lubrication means: Consistent frictional properties: In order to determine your torque value, you have to understand, and solve for your K-factor. K-factor, which can also be called “nut factor,” is an experimental number. It is not adequate to use a friction coefficient or a friction factor calculation.
What is Bolt Lubricant?
Any lubricant is designed to reduce friction and wear between two surfaces in contact. Bolt lubricant is a little more complicated than that.
What does it mean to lubricate a stud?
Proper lubrication means that you’ve put lubricant on every thread so that the valley of the stud is full. See the demonstration at the 1:20 mark in the video below ( click here to jump to it, but note: that link will take you to YouTube):
When you apply lubricant to a bolt, should you see a bead of lubric?
When you apply lubricant, be certain that all valleys of the stud bolt threads are filled. Once the nut is hand tightened, you should see a bead of lubricant extruding from beneath the nut. This indicates that the lubrication has been applied to all working surfaces.
What is the best lubricant for bolted joints?
Recently the petrochemical industry has moved to molybdenum disulfide, which is also called “moly” lube. Currently this is the best type of lube for assembling bolted joints, because it does not cause hydrogen embrittlement if mixed with the correct chemicals.
How much stress is needed for bolts?
No lubrication: You will see that, without lubricant, bolt stress is lower than our target bolt stress of 40 Ksi. In the video above, our test on unlubricated studs test averages 28.8 Ksi, with the low amount being 27.3 and a high of 31.
What are the three types of lubricants?
Investigated lubricants included oils, greases, and solid film lubricants that were applied to the threads of the fastener and the nut, and the turning bolt underhead surface as well as the joint surface in contact with the bolt head. The oils tested were mineral oils with different viscosities, i.e. 21cst, 115cst, 1000cst respectively at 40°C. Three types of grease were tested; namely, regular grade, pure nickel special, and heavy metal free grease. For the solid lubricants, an olefinic type, an olefinic base with a polytetrafluoroethylene additive, and an olefinic base with an inorganic additive (Molybdenum disulfide), were applied. Class 8.8 M12 fasteners with both fine and coarse threads were used. The experiments were carried out using a Laboratory Fastener Testing System which measures the input torque, the fastener tension, the thread friction torque, and the angular rotation of the bolt head. The system computes the thread and bearing friction coefficients from the measured data. In each test, the fastener was repeatedly tightened and loosened five times. The tests were also conducted under different tightening speeds, varying from 1 rpm to 100 rpm. The nut factor, the coefficients of thread and the underhead friction were obtained from the experiments. The effects of the number of tightening and loosening cycles, the tightening speed, and the type of lubricant on friction and nut factor were investigated. It was found that lubrication had a significant effect on the friction and the torque-tension relationship in threaded fasteners. Presented at the STLE/ASME International Joint Tribology Conference in San Antonio, Texas, October 23-25, 2006Review led by Thierry Blanchet
What is the mathematical formulation of the tightening process in bolts?
A mathematical formulation of the tightening process in bolts is presented, and from this design charts were developed which enable the determination of the necessary tightening torques for the maximum usable preloads. An apparatus which measures the friction coefficients between the threads and under the nut is described. For each bolt and friction coefficient under the nut it was found that there was a critical value of thread friction coefficient which gave a maximum tightening torque. (V.B.D.)
What is pre stress bolt?
Pre-stressed bolted joints are widely used in civil structures and industries. The tightening force of a bolt is crucial to the reliability of the joint connection. Loosening or over-tightening of a bolt may lead to connectors slipping or bolt strength failure, which are both harmful to the main structure. In most practical cases it is extremely difficult, even impossible, to install the bolts to ensure there is a precise tension force during the construction phase. Furthermore, it is inevitable that the bolts will loosen due to long-term usage under high stress. The identification of bolt tension is therefore of great significance for monitoring the health of existing structures. This paper reviews state-of-the-art research on bolt tightening force measurement and loosening detection, including fundamental theories, algorithms, experimental setups , and practical applications. In general, methods based on the acoustoelastic principle are capable of calculating the value of bolt axial stress if both the time of incident wave and reflected wave can be clearly recognized. The relevant commercial instrument has been developed and its algorithm will be briefly introduced. Methods based on contact dynamic phenomena such as wave energy attenuation, high-order harmonics, sidebands, and impedance, are able to correlate interface stiffness and the clamping force of bolted joints with respective dynamic indicators. Therefore, they are able to detect or quantify bolt tightness. The related technologies will be reviewed in detail. Potential challenges and research trends will also be discussed.
What is the role of electroplated bolts?
In the present work, for the first time, the role of each layer of the bolt coating (i.e., electroplating, passivate and topcoat layer) on the coefficient of friction of a bolted joint were experimentally and systematically investigated. The coefficient of total friction (μtot), coefficient of friction between threads (μth), and coefficient of friction between bearing surfaces (μb) were calculated by a torque-tension testing system and compared under different experimental conditions. It was found that the μth, μb, and μtot on pure Zn plating was slightly different from that on Zn-Ni alloy plating; the black passivate had lower μth, μb, and μtot than the clear passivate when topcoats were applied; and the topcoat played a dominant role in reducing the μtot. Other factors including washer material, nut plating and heat treatment were also studied. Results showed that the aluminum washer gave a dramatically higher μb than the steel washer. The tested plating layers of Zn, Ni, and Zn-Ni alloy on the nut didn’t significantly affect the μth. Tested bolts could withstand heat up to 182 °C for 1 h. Higher temperature or longer heating time increased all the μth, μb, and μtot. These findings will increase the understanding of the factors that will affect the friction coefficients in electroplated bolts and will help to better design bolted joints.
Does lubrication affect torque?
It was found that lubrication had a significant effect on the fri ction and the torque-tension relationship in threaded fasteners. Presented at the STLE/ASME International Joint Tribology Conference in San Antonio, Texas, October 23-25, 2006Review led by Thierry Blanchet.
Why is torque used in bolt tensioning?
Torque is used as the bolt tensioning standard simply because it is easiest for the average technician to measure. As you are finding out it is a pretty bad way to do precision assemble. It is close enough for government work but for very high demand applications, there is no substitute for measuring bolt stretch which is the base design parameter. Torque is simply an easily measured secondary indicator. For highly stressed industrial applications technicians use instrumentation to measure bolt stretch only and aren't concerned with the torque level. Chilton and other assembly manuals specify torque levels that assume a certain thread condition and lubrication that yield a known range of bolt stretch. Change the lube or thread condition and the torque needs to be re-calibrated to the desired stretch. You are getting vague answers because there is no 100% way to tell what the effect on bolt stretch without measuring it directly. Best bet is to defer to the bolt or lube suppliers who have hopefully done the lab work to calibrate torque spec to bolt stretch.
How much torque is used to overcome friction?
Consider that when torqueing a bolt, about 40% of the force applied is used to overcome the friction in the threads. About 50% of the torque applied goes to overcoming face friction. The remaining 10% is applied to preload.
How to test a bolt?
Try this simple test. Take a block of steel drill a hole through it and put a bolt and nut together thru it dry. Take a set of mic's and check the length of the bolt. Now start torquing the bolt in like 10 ft/lb increments. Check the length after every pull. Take it apart and put some molly lube on it and try again. Record the lengths per ft/lb dry and with molly you'll be surprised!!!! If you really want to get wild try it with different grade bolts...
Why are fasteners engineered?
Of course if your building spacecraft or high performance aircraft where each fastener has only a minimum safety factor to save weight, in those cases the fastening system would be engineered and carefully spec'd to ensure the stresses are controlled and duplicated from lab to real world.
Can I use ARP torque on other bolts?
I would not apply "ARP" suggested torque values to other bolts based just on using their moly-lube. There is more to the suggested values that the lube as the fastener material itself is different too.
Can you use moly oil on a fastener?
There is no advantage at all in using a moly (or any other "slippery stuff") on fasteners. Best procedure is to use 30# motor oil and make sure that the threads are absolutely clean. For cleaning the threads, use only a thread chasing set. Do not use a tap and die set to clean the threads as these will actually remove metal from the threads. The amount of metal removed by tap & die set is very minute, but it will affect the clamping force of the fastener.
Can you measure rod bolt stretch?
Rod bolt stretch can be measured, but cap bolts are another story. The higher performance lubes have definite advantages, but only if they are matched with the corresponding torque values.
Why is friction important in torque?
For torque to provide predictable and repeatable loading, friction must also be predictable and repeatable. Fastener lubrication is one of the most effective ways to accomplish this. Keep in mind that other factors can affect friction—such as corrosion and re-used components.
How does each fastener affect the other?
As they tighten the fasteners , each fastener’s load affects the others as each is tightened. To help ensure uniform loading on all the fasteners, they must be brought up evenly by tightening in stages and in a staggered manner. Historically, the star pattern has been used for the tightening sequence.
Is torque the most accurate way to tension a fastener?
A word of caution, torque is not the most accurate way to tension a fastener. The amount of tension achieved from torque is affected by a number of variables. Friction is the most important, and it is difficult to control. High friction results in low tension, and low friction results in high tension. At best, torque tension results will vary in ...
What are the benefits of loctite threadlockers?
Benefits of Loctite® Threadlockers •• Lock nuts and bolts against vibration and thermal expansion •• Seal against corrosion and leakage •• Reduce inventory costs •• Suitable for all shapes and sizes of fasteners •• Act as a thread lubricant ••Maintain critical adjustments of the assembly •• No on-torque adjustments needed •• High chemical resistance
Can you reduce torque when using loctite?
I never reduce torque values when using Loctite, anti-zeize, or oil. The torque specifications were intended for free, easy turning fasteners.
Does loctite change torque?
You may see a lot of different opinions on this. However, Loctite suggests that there be no change in "on-torque" values . So, torque to dry spec for all Loctite Purple, Blue, Red...
Is loctite a slick lubricant?
I ask because Loctite is not a slick, greasy lubricant like anti-seize is. It is simply wet, and you are only putting a few drops on several threads (usually). For instance, if you use Loctite on the brake caliper mounting bracket bolts, would it be prudent to reduce the torque spec by 20%? Thanks.
Do you change torque figures on a brake?
Do not change the torque figures. I have never personally come across any brake assembly that required Loctite. Why are you wanting to use it?
Do you lubricate a torque bolt?
Torque nuts & bolts with clean and dry threads unless otherwise specified in the maintenance manual. Do not lubricate nut or bolt threads unless otherwise specified in the maintenance manual.
Can you get threads dry when tearing stuff down?
It is nearly impossible to get threads dry when tearing stuff down and putting it back together. That is why, unless you can get it absolutely clean and dry, it is far easier to just use the Loctite and suitable REDUCED torque specs that go along with it. I'm outta here guys.
Why don't you use thread lubricant?
That’s where some of the caution about using thread lubricant comes from, and why some companies might decide that, even though it has beneficial properties, they won’t use it because they’re not sure what the effect on bolt tightness will be.
Why is torque used as an indicator?
A Culture of Torque. The industry standard is to use torque as an indicator for bolt tightness—and that’s where the problem begins. Torque is a rotational or twisting force, but the torque reading on a wrench doesn’t guarantee that a bolt is tight. That’s because the real holding force is caused by the inclined plane of ...
What is the force that pulls a bolt back?
It’s this pulling back force, called the “clamp force” that actually maintains the tightness of the joint. So, torque isn’t the true measure of bolt tightness—it’s tension.
What is lubricant made of?
Today, a wide variety of lubricants, mostly made from petroleum, are used on the threads of bolted joints. These lubricants can be wonderful—
Is torque always tight?
Torque is not always Tight. Obviously lubrication of threaded bolts has lots of benefits, but with it comes the overriding concern that the lubricant will change the torque required to develop proper tension on the bolt—and how that could affect the integrity of the joint. Some estimate that adding a lubricant could reduce ...
Is torque a measure of tightness?
So, torque isn’t the true measure of bolt tightness—it’s tension. But lubrication on the bolt threads—and a whole host of other factors—can cause fluctuation in torque readings. So once you add a lubricant of any kind to the threads, all bets are off as to whether the same torque setting will truly secure the bolt.
