1. BOLTED JOINT ASSEMBLY WIND ENERGY FIELD SERVICE TECHNICIANS
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
BOLTED JOINT ASSEMBLY WIND ENERGY FIELD SERVICE TECHNICIANS
TIGHTENING WITH TORQUE “ONE GOOD TURN DESERVES ANOTHER”
This presentation gives an overview of the background to torque controlled tightening. The key features of this presentation are:
Torque - What is it?
Clamp force - bolt preload
How the clamp force is related to the torque
Torque tightening a bolt to failure
Normal torque tightening range
What happens if the torque value is too high
What happens if the torque value is too low.
The distribution of the torque in the threads and under the nut face
Use of a lubricant and the condition of the bolt
Determining the right torque value
Using a table to look up the right torque value
Experimental determination of the torque value
Calculating the torque value
Calculating the bolt preload
The nut factor method
The full torque-tension equation.

2. 1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
The following material is intended to make you aware of the commonly accepted and recognized principles and methods used in assembling bolted joints. However, every possible application of these methods cannot be foreseen and these general guidelines do not supersede any other applicable rules or regulations.
ALWAYS FOLLOW CURRENT COMPANY AND LOCAL SAFETY RULES AND PROCEDURES WHEN PERFORMING ANY OF THE WORK DESCRIBED IN THIS PRESENTATION.
The authors and sponsors of this course have no control over, and assume no responsibility for any damage, injury or work interruptions due to any person’s use of, or reliance upon the generally accepted methods and principles contained in this course.
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No course can cover all possibilities and address all problems. The key is to know what to look for, and where to go to get the answers.
Hopefully that is what you will take away from this course.

3. Too much of a good thing…
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly

4. Torque Tightening
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
Specifying a torque value is the most common way of applying control to the tightening process.
The method is normally referred to as torque tightening or torque controlled tightening.
Torque tightening, or torque controlled tightening as it is sometimes called, is when a torque is specified as a measure of how tight a threaded fastener should be. Indirectly controlling the bolt preload by specifying a tightening torque is the most commonly used method for controlled tightening.

5. 1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
What is Torque?
Torque is the product of the force applied times the distance it is applied over i.e.
Torque = Force x Length
Torque is force acting on a lever to produce a turning effect i.e Torque = Force x Length. In engineering science, the term moment is sometimes used instead of torque.
Usually expressed as: foot-pounds (ft/lbs) or inch-pounds (in/lbs) ft/lb = 12 in/lb

6. If we apply 100 lbs. to a wrench which is 1 foot long, the torque is:
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
Applying a Torque?
If we apply 100 lbs. to a wrench which is 1 foot long, the torque is:
Torque = 100 x 1 = 100 ft/lbs
In metric units torque is usually expressed in Newton-meters (Nm) or Kilogram-meters (Kgm)
If the force applied to the spanner is measured in newtons and distance is measured in metres then the torque is newton-metres and the abbreviation is Nm. Similarly, if the distance is measured in feet and the force in pounds then the torque is pound-feet and the abbreviation is lb-ft.
1 Nm = about .73 ft/lb
100 Nm = about 73 ft/lb

7. If you want more torque, get a longer lever or a bigger hammer!
Increasing the Torque?
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
300 lbs =
3 ft. x 100 lbs. = 300 ft/lbs
1 ft. x 300 lbs. = 300 ft/lbs
Applying a large force using a small lever arm can give the same torque as applying a small force on a long lever. For example, applying 1000 N on a lever 0.1 metres long will give the same torque as applying 100 N at 1 metre i.e. a torque of 100 x 1 = 100 Nm.
If the force applied to the spanner is measured in newtons and distance is measured in metres then the torque is newton-metres and the abbreviation is Nm. Similarly, if the distance is measured in feet and the force in pounds then the torque is pound-feet and the abbreviation is lb-ft.
Sometimes the torque units are expressed as ft-lbs. In this presentation the units lb-ft are used so that there is no confusion to energy units that are expressed in units of ft-lbs.
If you want more torque, get a longer lever or a bigger hammer!

8. TENSION TORQUE IMAGINE – YOUR BATHROOM SCALE IN YOUR BENCH VISE
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
IMAGINE –
YOUR BATHROOM SCALE IN YOUR BENCH VISE
TENSION
TORQUE
To illustrate the difference in the concept of torque and pre-load or tension imagine that you put your bathroom scale in a vise. Depending on the length of the bar in the vise and the amount of force you tighten it with, you can put a lot of squeeze on the scale. It is that tension that we are looking for and for any given set of circumstances we can establish a relationship between the amount of torque we apply to the screw and the resulting tension.
Change the weight or distance and you change the load by a predictable amount
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CHANGE WEIGHT OR DISTANCE AND YOU CHANGE LOAD

9. TENSION or LOAD TORQUE In Bolting We Are Interested In NOT
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
TENSION or LOAD
NOT
TORQUE
(But Since Load Is Difficult To Measure
We Measure Torque As Away To Approximate Load)

10. DOUBLE THE TORQUE = DOUBLE THE LOAD
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
Clamp Force and Torque
DOUBLE THE TORQUE = DOUBLE THE LOAD
How the clamp force and torque are related is sometimes referred to as the torque-tension relationship. This defines how much torque will be converted into preload. Below the yield limit of the material, the bolt preload is proportional to the torque applied. For example, if a torque of 250 lb-ft produces lb preload, a torque of 500 lbf-ft will produce lb.
T = k d f
If the clamp force provided by the bolts is not sufficient, gasket leakage will occur. On joints without a gasket, joint movement can occur, leading to fretting of the surfaces. This can reduce the bolt tension making it easier for further movement to occur and the bolt to self-loosen. Ensuring that the joint is tight is vital to ensuring that failure will be prevented!
Below the yield limit of the material (in the elastic range of the bolt) preload is proportional to the torque applied.

11. Plates being pulled together
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
Yield of
the bolt
material
Maximum
Tensile
Strength
Bolt thread
‘necking’
occurring
Plates being pulled together
Bolt
Failure
If a bolt is tightened and the clamp force (the preload) is measured together with the angle of rotation of the nut, a graph like the one shown above can be created.
Initially when the torque is applied to the nut, the joint plates are pulled together. Once there is firm metal to metal contact, the graph becomes a straight line until the yield of the bolt is reached and this linear relationship no longer holds. The clamp force continues to increase until the tensile strength of the bolt material is reached. Following this point the thread starts to ‘neck’ (its diameter reduces) until bolt failure occurs.
If we keep tightening a bolt, sooner or later it will reach the limit of its strength and will break.
Graph shown was experimentally determined for a particular joint.

12. ?? HOW MUCH TORQUE IS RIGHT FOR A PARTICULAR BOLT? BOLT DIAMETER
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
HOW MUCH TORQUE IS RIGHT
FOR A PARTICULAR BOLT?
In Your Work You Will Most Often Be Given Torque
Specifications In The Form Of A Torque Chart.
Behind The Numbers Are Factors Which Can Change
The Torque Values - Some Of The Major Ones Are:
BOLT DIAMETER
BOLT STRENGTH
DESIRED TENSION
THREAD PITCH
BOLT CONDITION
LUBRICATION ??
Now that we understand the difference between torque and tension or load let’s consider how much torque is right for a particular bolt.
There are many factors that affect the answer.
Some of the most important are:
Bolt Diameter
Strength of the bolt material
The desired percent of yield
The thread pitch
The condition of the bolt
And Lubrication
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13. Everything Else Equal, A Big Bolt Will
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
BOLT DIAMETER
Everything Else Equal, A Big Bolt Will
Stand More Torque Than A Small One
The first factor that affects how much load we can put on a bolt is it’s diameter.
BOLT DIAMETER
Everything else equal, a big bolt will stand more torque than a small one.
DUHH!!!!
This sounds a little obvious.
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14. Tension ( Remember, This Is What We Really Want)
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
BOLT DIAMETER (cont.)
This is true because if you look at the ends of the bolts there is more cross sectional area (more square inches of steel)
Tension ( Remember, This Is What We Really Want)
Is Measured In Pounds Per Square Inch
AREA OF A CIRCLE
Radius = ½ Diameter
π = 3.14
Area = (π r2)
At the risk of sounding like Homer Simpson the point is that PRE-LOAD or TENSION (REMEMBER THIS IS WHAT WE REALLY WANT) is measured in pounds per square inch (P.S.I.)
square inches of what, you ask. - square inches of cross section of the bolt.
So remembering your high-school geometry, pi times the radius squared gives you the area of a circle or the area of the cross section of the bolt
a 1” diameter bolt has a cross section area of just about .8 square inches
while a 2” bolt has a cross section of 3.14 inches or four times the area.
therefore a 2” bolt can carry 4 times the load of a 1” bolt of the same material!
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2” bolt = 3.14 sq.in.
4 times as much as a 1” bolt
1” bolt = .79 sq.in.

15. TWICE THE WIDTH = 4 TIMES THE AREA
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
Think about it…
The same thing would be true using square bars.
TWICE THE WIDTH = 4 TIMES THE AREA 1 1
2 in. 1 1
1 in. 1 1
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1 in.
2 in.

16. Brass Steel BOLT STRENGTH
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
BOLT STRENGTH
Which bolt do you think could stand more stress without permanently deforming?
An obvious question?
Brass
Write your answer here!
Steel

17. 1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
Less obvious but true –
Steels have different strength characteristics, i.e. the ability to withstand stress without breaking.
Bolts are marked to show those differences:
In the “inch standard” bolts are marked by a “strength grade”
In the “metric standard” bolts are marked by a “property class”
More details on the strength characteristics of both inch and metric fasteners are provided in a separate section.

18. 1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
The above chart illustrates the minimum specified yield strength of the popular bolting materials. (Note that 1 ksi is 1000 psi.) In general the SAE J429 standard applies to inch based fasteners and the ISO 898 standard to metric fasteners. The ASTM A193 standard applies both to metric and inch based fasteners.
For some of the materials, such as B7, the strength decreases as the bolt diameter increases: the specific minimum yield strengths are:
SAE J429 Grade 5 1/4 thru’ 1 inch 92 ksi (634 N/mm²)
Over 1thru 1-1/2 81 ksi (558 N/mm²)
SAE J429 Grade ksi (896 N/mm²)
ASTM A193 B7 < 2.5 inch 105 ksi (724 N/mm²)
2.5 < 4 inch 95 ksi (655 N/mm²)
4 < 7 inch 75 ksi (517 N/mm²)
ASTM A193 B7M <= 2.5 inch 80 ksi (552 N/mm²)
ISO 898 Property Class 8.8 <= M N/mm² (93 ksi)
>M N/mm² (96 ksi)
ISO 898 Property Class N/mm² (136 ksi)
B7M

19. Yield of the bolt material
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
Normal tightening range.
In order to ensure that the bolt does not approach its yield strength either during tightening or afterwards when loading is applied to the joint, bolts are tightened so that a tensile stress is present in the bolt between 40% and 70% of the yield strength.
Bolts in machine joints are typically torqued so that the induced stress is between 40% and 70% of their yield strength.
SOME WIND TURBINE BOLTS MAY BE TIGHTENED CLOSE TO 90%

20. Bolts Are Tightened To A Given Percent
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
DESIRED TENSION
Bolts Are Tightened To A Given Percent
Of Their Yield Based On The Engineered
Requirements Of The Job
Yield L O A D
70%
Most metal-to-metal joints
done at 70%+ of yield
50% of yield
Most joints with Gaskets
done at 50% of yield
Just because a bolt will stand 200,000 lbs of pre-load doesn’t mean that the job requires it to do so. When you are handed a torque number for a particular set of bolts the engineer who designed the machine decided what percent of yield of the bolts he wanted, giving enough clamping force to hold the joint together and enough reserve to withstand any dynamic shocks without yielding the bolts.
Think about the lug bolts on you car wheels. Normally they are torqued to about 75 ft/lbs. They would probably hold your tires on the car at 50 ft/lbs. And they would probably stand 125 ft/lbs without damage to the lugs. Driving down the highway you would not be able to tell the difference. You just want the tires to stay on. This broad range of ability to stand varying loads is one of the most valuable and useful properties of steel.
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21. It Can Make A Difference Whether The Threads Are Coarse Or Fine
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
THREAD PITCH
It Can Make A Difference Whether The
Threads Are Coarse Or Fine
Remember – it has to do with the angle of attack of the inclined plane…
steep
flat
On most torque charts it will indicate the threads per inch on the bolt. Almost every bolt you will ever deal with though will be the standard 8 threads per inch which is referred to as a coarse thread or 8UNC (Uniform National Code)
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Finer threads are flatter and turn easier for that reason but that advantage is swallowed up by the increased surface area and therefore friction in the fine threads. Don’t worry, just be sure that your bolt matches what the torque chart assumes.
(If you would like to know more see the discussion on thread patterns and metric thread pitch in your student manual)

22. New Turns Easier Than Old, Smooth Turns Easier Than Rough
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
BOLT CONDITION
New Turns Easier Than Old,
Smooth Turns Easier Than Rough
Even lubrication can’t make up for corroded or damaged threads either on the nut or on the bolt.
Bolts can generally be re-used if they have not been strained beyond their yield point or otherwise damaged.
If you are going to re-use the bolts and nuts you must examine and clean the threads before lubrication and re-assembly.
If your application is a critical one it may be best to replace the bolts rather than re-use them. Mixing old and new bolts on the same flange or application is not recommended. In this case equal torque will not produce equal load and you may have leaks and joint failure.
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23. Condition of the Stud and Bolt
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
Check the bolts and nuts for corrosion and the thread for nicks. These will adversely affect the bolt preload.
Prior to their installation, bolts and nuts should be checked for corrosion and defects like thread nicks. Such issues can affect the torque-tension relationship so that more torque is lost in friction rather than producing tension in the bolt.
GARBAGE IN… GARBAGE OUT!!

24. FRICTION A Lubricated Bolt Will Turn Easier Than A Dry One LUBRICATION
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
LUBRICATION
A Lubricated Bolt Will Turn Easier
Than A Dry One
BECAUSE OF
FRICTION
Lubrication
Again you already know that a little WD-40 on your tire lug nuts makes them go on, and come off easier. But you may be surprised to know how much of a difference a little lube makes in the torque required to achieve the desired bolt pre-load.
On a typical dry nut and bolt combination it may require 30% of your turning force just to overcome friction in the threads and under the nut where it scrapes against the washer or the flange.
If you grease those two surfaces you will be able to achieve the same amount of bolt stretch while only wasting 10% of your effort overcoming friction – ONLY 1/3rd OF THE TORQUE VS. DRY.
Pay attention to whether your torque chart is for a lubricated or a dry torque, and if possible what lubricant they are telling you to use. Once again this may explain why two torque charts don’t agree!
While we are on the subject of lubrication it is important to note that since what gets bolted together usually has to be unbolted, the use of modern never-seize products, especially in high temperature applications will keep you from galling threads and may cut the breakout torque in half. Follow the manufacturer’s or engineer’s recommendations as to lubricants.
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25. WE CALL THIS RATIO THE COEFFICIENT OF FRICTION
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
LUBRICATION cont.
MEASURING FRICTION
WEIGHT (10 LBS)
FORCE (2 LBS)
IN OUR SIMPLE EXAMPLE THE FORCE NECESSARY TO SLIDE THE BOOK PERPENDICULAR TO ITS WEIGHT IS:
2 lbs. / 10 lbs. = .2
WE CALL THIS RATIO THE COEFFICIENT OF FRICTION

26. 1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
LUBRICATION cont.
In other words, in our example it takes a force of 20% of the weight of the object to slide it over the surface of the table.
What do you think would happen to the coefficient of friction if the book were resting on ice? sandpaper? grease?

27. DRY FRICTION CAN BE 3 TIMES AS MUCH AS WITH GREASE!
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
LUBRICATION cont.
When steel slides against steel, the c.o.f. can be high
Steel on Steel (coefficients of friction)*
(dry) approximately .3 or 30%
(oiled) approximately .2 or 20%
(greased) approximately .1 or 10%
(read the slide)
DRY FRICTION CAN BE 3 TIMES AS MUCH AS WITH GREASE!

28. “DRY” TORQUE CAN BE 3 TIMES AS MUCH AS LUBRICATED TORQUE
LUBRICATION IS IMPORTANT BECAUSE OF ITS
HUGE EFFECT ON TORQUE
(TORQUE IN FT/LBS)
GRADE 8
BOLT DIA. NUT SIZE 60,000 P.S.I. AT THIS TORQUE
DRY OIL MOLY-GREASE
1" 1-5/8"
1-1/4" 2"
1-1/2" 2-3/8"
1-3/4" 2-3/4"
2" 3-1/8"
2-1/4" 3-1/2"
2-1/2" 3-7/8"
2-3/4" 4-1/4"
3" 4-5/8"
3-1/4" 5"
3-1/2" 5-3/8"
3-3/4" 5-3/4"
4" 6-1/8"
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
Let’s see if you got all of this.
On the sample chart what would be the recommended torque value for an 1-1/2” grade 8 stud lubricated with molybdenum di-sulfide (moly grease)?
The answer per this chart is 879 ft/lbs of torque. Note that if the same bolt had been dry, it would have take 2725 ft/lbs to achieve the same bolt load!
Incidentally these torque values will produce about 135,000 pound of load in this bolt one bolt.
A fully loaded tractor trailer weighs about 80,000 pounds, so this one bolt would almost carry two big rigs without yielding!
“DRY” TORQUE CAN BE 3 TIMES AS MUCH AS LUBRICATED TORQUE

29. THE DIFFERENCE IS DUE TO FRICTION!
(TORQUE IN FT/LBS)
GRADE 8
BOLT DIA. NUT SIZE 60,000 P.S.I. AT THIS TORQUE
DRY OIL MOLY-GREASE
1" 1-5/8"
1-1/4" 2"
1-1/2" 2-3/8"
1-3/4" 2-3/4"
2" 3-1/8"
2-1/4" 3-1/2"
2-1/2" 3-7/8"
2-3/4" 4-1/4"
3" 4-5/8"
3-1/4" 5"
3-1/2" 5-3/8"
3-3/4" 5-3/4"
4" 6-1/8"
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
EACH OF THESE TORQUES WILL PRODUCE EXACTLY THE SAME PRE-LOAD ON A 1-1/2” BOLT
THE DIFFERENCE IS DUE TO FRICTION!
80,000 POUNDS OF PRE-LOAD
THAT’S EQUAL TO THE WEIGHT OF A FULLY LOADED 18 WHEELER ON JUST THIS ONE BOLT!
Let’s see if you got all of this.
On the sample chart what would be the recommended torque value for an 1-1/2” grade 8 stud lubricated with molybdenum di-sulfide (moly grease)?
The answer per this chart is 879 ft/lbs of torque. Note that if the same bolt had been dry, it would have take 2725 ft/lbs to achieve the same bolt load!
Incidentally these torque values will produce about 135,000 pound of load in this bolt one bolt.
A fully loaded tractor trailer weighs about 80,000 pounds, so this one bolt would almost carry two big rigs without yielding!

30. SAMPLE TORQUE CHART SHOWING FACTORS AFFECTING TORQUE
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
SAMPLE TORQUE CHART SHOWING FACTORS AFFECTING TORQUE
PRE-LOAD 50% OF MINIMUM YIELD STRENGTH (TORQUE IN FT/LBS)
THREADS HVY.HEX GRADE GRADE 8
STUD DIA. PER INCH. NUT SIZE ,000 P.S.I. AT THIS TORQUE 60,000 P.S.I. AT THIS TORQUE
DRY MCHN.OIL MOLY-DS DRY MCHN.OIL MOLY-DS
1" 8 UNC 1-5/8"
1-1/4" " 2"
1-1/2" " 2-3/8"
1-3/4" " 2-3/4"
2" " 3-1/8"
2-1/4" " 3-1/2"
2-1/2" " 3-7/8"
2-3/4" " 4-1/4"
3" " 4-5/8"
3-1/4" " 5"
3-1/2" " 5-3/8"
3-3/4" " 5-3/4"
4" " 6-1/8"
Let’s see if you got all of this.
On the sample chart what would be the recommended torque value for an 2” grade 8 stud lubricated with molybdenum di-sulfide at 50% of minimum yield strength?
(let class give an answer)
(discuss the notation underneath the bolt grade headings concerning the pounds per square inch of tension or load achieved at theses torques. Note that the chart assumes 50% of yield will be achieved if these torques are applied and a grade 5 has a yield of 90,000 lbs. Per square inch of cross section (.5 x 90,000 = 45,000 pounds per square inch at the specified torque.) whereas the grade 8 bolt has a yield of 120,000 pounds per square inch of cross section (.5 x 120,000 = 60,000 pounds per square inch at these torques)
Heavy Hex Nut is 1.5 stud diameter plus 1/8”

31. Let’s Try A Few Questions To Ensure
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
Let’s Try A Few Questions To Ensure
We Understand About Torque And Load
Read the slide)
Please take a few minutes to complete exercise 1 and discuss it.
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(Quiz #2)

32. Name 3 factors that directly affect the torque value for a given stud:
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
QUIZ
Name 3 factors that directly affect the torque value for a given stud:
A.____________________________________________
B.____________________________________________
C.____________________________________________
2. T / F A two inch diameter bolt can carry four times as much load as a similar one inch diameter bolt.
(Cont.)

33. QUIZ grade ___? grade ____?
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
QUIZ
3. Which of these two bolts is able to carry more load and withstand more torque?
grade ___? grade ____?

34. What size socket is required to tighten this nut? ______
QUIZ
4. Using the torque chart below what is the desired torque for a /4” grade 8 stud with no lubrication? ___________
What size socket is required to tighten this nut? ______
5. T / F It is OK to mix bolts of different grades on the same flange as long as you calculate the torque properly for each grade.
6. T / F Once a bolt or stud has been used it should be replaced.
7. In the metric system an M45 bolt corresponds to:
A. Bolt diameter of 45 mm B. Socket size of 45 mm
C. A yield pt. of 45 kN D. None of the above
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
(Cont.)

35. 1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
SAMPLE TORQUE CHART SHOWING FACTORS AFFECTING TORQUE
PRE-LOAD 50% OF MINIMUM YIELD STRENGTH (TORQUE IN FT/LBS)
THREADS HVY.HEX GRADE GRADE 8
STUD DIA. PER INCH. NUT SIZE ,000 P.S.I. AT THIS TORQUE 60,000 P.S.I. AT THIS TORQUE
DRY MCHN.OIL MOLY-DS DRY MCHN.OIL MOLY-DS
1" 8 UNC 1-5/8"
1-1/4" " 2"
1-1/2" " 2-3/8"
1-3/4" " 2-3/4"
2" " 3-1/8"
2-1/4" " 3-1/2"
2-1/2" " 3-7/8"
2-3/4" " 4-1/4"
3" " 4-5/8"
3-1/4" " 5"
3-1/2" " 5-3/8"
3-3/4" " 5-3/4"
4" " 6-1/8"
Let’s see if you got all of this.
On the sample chart what would be the recommended torque value for an 2” grade 8 stud lubricated with molybdenum di-sulfide at 50% of minimum yield strength?
(let class give an answer)
(discuss the notation underneath the bolt grade headings concerning the pounds per square inch of tension or load achieved at theses torques. Note that the chart assumes 50% of yield will be achieved if these torques are applied and a grade 5 has a yield of 90,000 lbs. Per square inch of cross section (.5 x 90,000 = 45,000 pounds per square inch at the specified torque.) whereas the grade 8 bolt has a yield of 120,000 pounds per square inch of cross section (.5 x 120,000 = 60,000 pounds per square inch at these torques)
Heavy Hex Nut is 1.5 stud diameter plus 1/8”

36. Bolt diameter, bolt grade, lubrication
1 BOLTING ASSEMBLY TRAINING - INTRODUCTIONNotes from the Training Course on Bolting Assembly
Quiz answers:
Bolt diameter, bolt grade, lubrication
True. Double the diameter and you quadruple the area, and strength is a function of area
The one on the right, grade 8. the other is a grade 5.
6501 Ft/lbs. 3-1/8” socket ((bolt size x 1.5)+ 1/8)
False. Do not mix grades of bolts on the same joint.
False. Not unless it is damaged or you are instructed to always replace A.