Atlas_Copco_Pocket Guide_TurboTight_UK__.pdf - Atlas Copco

Pocket Guide to TurboTight ®

Contents 

Page 

1 Introduction ..................................................................... 4 

1.1 TurboTight ® simplified ............................................... 4 

1.2 Background ................................................................. 4 

1.3 Why is it now possible to use TurboTight ® ? .............. 5 

1.4 Theory ......................................................................... 6 

1.5 In practice .................................................................... 6 

2 Key benefits of TurboTight ® ........................................... 7 

2.1 How are cycle times reduced? .................................... 8 

2.2 How is reaction force reduced? ................................ 10 

2.3 How come set-up is so easy? .................................... 10 

2.4 How does TurboTight® provide energy savings? ... 10 

3 Ergonomics ...................................................................... 12 

3.1 Letting the tool absorb the reaction force ................. 12 

3.2 Less heat development .............................................. 13 

4 Accuracy .......................................................................... 15 

5 Clamp force ..................................................................... 16 

6 Relaxation ........................................................................ 18 

7 Residual torque ............................................................... 18 

8 Torque scatter ................................................................. 19 

9 Where to use TurboTight ® ............................................ 19 

10 Recommendations relating to TurboTight ® ................ 20 

10.1 TurboTight ® and tool extensions ............................. 21 

10.2 The limitations of TurboTight ® ............................... 21 

10.3 How to set up TurboTight ® ..................................... 23 

10.4 TurboTight ® and the customer ................................ 26 

10.5 FAQs – Frequently Asked Questions ...................... 27 

POCKET GUIDE TO TURBOTIGHT ® 

3

The inertia of the car traveling uphill 

is used to offset the torque from 

the engine and help stop the car at 

the top. Similarly, TurboTight ® uses 

the tool’s inertia to counteract and 

minimize the force transmitted to the 

operator’s hand and arm. Thus, the 

end of the tightening feels soft. 

4 POCKET GUIDE TO TURBOTIGHT ® 

1. Introduction 

1.1 TurboTight ® simplified 

TurboTight ® is a new and revolutionary tightening strategy 

that dynamically reads joint stiffness during a tightening cycle. 

It calculates the energy needed to reach the target torque and 

regulates the tightening speed to provide the tightening energy 

required to ensure reliable accuracy. Reaching the target torque 

causes the regulator to stop the motor and the tightening is 

complete. 

In simple terms, TurboTight ® can be compared to a car traveling 

up a hill to a parking lot. The driver regulates the speed 

with the gas pedal and uses the brakes to stop the car immediately 

on reaching the target parking lot. 

Thus, a tightening can be controlled at a higher speed than 

ever before. One of the main reasons for this is an improved 

sampling rate between the controller and the tool. 

1.2 Background 

TurboTight ® has been patented as a new and innovative power 

tool control tightening strategy. It was developed to improve 

operator ergonomics and thus increase operator comfort. 

TurboTight ® is fast and, because it uses the inertia of the tool, 

the reaction force to the operator is minimal, delivering the 

best ergonomic behavior during tightening. The ergonomic

Fast Ergonomic Low impact Accuracy 

goal is to let the tool absorb the reaction force. The aim was for 

the operator to experience a similar reaction force as with air 

tools, i.e., a clutch tool feeling on hard joints. 

In parallel with the improved ergonomics, tightening accuracy 

was maintained at the respective system levels. Tensor STR 

using TurboTight ® will deliver ±5% and Tensor ES will deliver 

±7.5% accuracy (over 6σ). 

TurboTight ® is extremely easy to set up. In fact, it can be described 

as a “set and go” tightening strategy. 

1.3 Why is it now possible to use TurboTight ® ? 

The Power Focus 6 Series uses an advanced technology compared 

to the Power Focus 4000. It has higher sampling, communication 

and calculation rates in both the Power Focus and 

the tool. The increased processing speed between the Power 

Focus and the tool, the optimized algorithm and the tightening 

knowledge Atlas Copco has gained during the past 10 years 

has helped us to develop this revolutionary tightening strategy. 

TurboTight ® is a high-tech tightening 

strategy that makes the tool 

operator’s job more comfortable, 

reduces cycle times and speeds 

up production. It took Atlas Copco 

specialists 10 years to develop 

based on extensive know-how and 

experience. 

With TurboTight ® the torque reaction 

is so small that the operator can 

hold the tool in one hand without 

experiencing a jerk at the end of the 

tightening. This is particularly true in 

the case of hard joints. 


5

Example: Signal sampling rate, Power 

Focus 4000 vs. Power Focus 600/6000 

Series. 

Sampling frequency on Power Focus 

600/6000 controllers is considerably 

higher than on the Power Focus 4000. 

This enables TurboTight ® to calculate 

when the correct final torque is 

reached and stop the tool in the shortest 

possible time and with the lowest 

possible reaction force. 


Power Focus 600/6000 

Power Focus 4000 

1.4 Theory 

The innovative idea behind TurboTight ® is to control the 

speed of the motor so that the rotational energy E r of the motor 

is equal to the energy E t which is required to complete the 

tighten ing to the target torque. To calculate the energy required 

to fasten an ideal linear joint, TurboTight ® needs to know the 

final torque and the tightening angle, or the target torque and 

the torque rate. The rotational energy can be calculated from 

the rotor inertia and rotor speed. 

1.5 In practice 

TurboTight ® is activated after the joint has been brought to 

snug tightness, but not tightened to the target torque. The snug 

level is detected by a torque threshold (rundown complete), 

which is manually adjustable. After the snug level is reached 

the torque rate k starts being calculated. 

The torque signal from a real tightening analysis contains 

mechanical and electrical noises and many other kinds of 

disturbances. Also, in handheld applications, operators 

constantly move tools during a tightening sequence. 

Since all the disturbances tend to distort the torque measurement, 

the torque rate k is automatically filtered during the calculation 

phase. Using the filtered k value the speed is always 

calculated and adapted to the condition of the joint.

2 Key benefits of 

TurboTight ® 

Reduced cycle times 

TurboTight ® optimizes the tightening speed to achieve the 

fastest possible tightening that still ensures reliable accuracy. 

The results are: 

• Possibility to remove bottlenecks, 

• Possibility to rebalance assembly lines due to increased 

cycle rate, 

• Less heat development, a cooler tool during operation. 

Reduced reaction force 

With optimized tightening speed, the torque builds up faster, 

reducing the amount of force transmitted to the operator’s 

hand. 


• Reduced operator fatigue and thus reduced 

risk of injury, 

• Improved operator comfort during tightening, 

• Reduced need for reaction absorbing devices in 

certain situations, thus less cost and reduced 

tool weight. 

Torque 

Rundown 

complete 

Torque 

Final torque 

40 Nm 

Snug tightness 

5 Nm 

∆ Angle 

Target 

torque 

Torque rate = 

∆ Torque 

∆ Torque 

∆ Angle 

Angle 

Angle 

TurboTight ® is activated 

after the joint has been 

brought to snug tightness. 

After the snug level is 

reached the torque rate 

starts being calculated. 

Ergonomics are improved since less 

muscle force is required from the 

operator’s arm to counteract the 

torque reaction. 

With TurboTight ® , tightening times are 

cut by 0.6 seconds per bolt. After only 

100,000 tightenings, the time savings 

will be 60,000 seconds, equivalent to 

an amazing 16 hours! This enables the 

production line to be rebalanced for 

optimum flow. 

Tightening 

angle 

Avoid 

bottlenecks 


7


Easy set-up 

TurboTight ® is designed to be extremely easy to set up. 

In most cases, you just need to set the target torque and you’re 

ready to go. Exceptions are discussed in the following chapters. 

In such cases please contact your local Atlas Copco Tools 

representative for support. 


• Time savings during set-up, 

• Less time and money spent on training, 

• Work rotation enabled. 

Sustainability 

Using TurboTight ® results in shorter tightening cycles. This 

in turn means less heat development and thus a cooler tool. 

It also helps to reduce energy consumption and prolong tool 

lifetime in high-cycle environments. 

2.1 How are cycle times reduced? 

TurboTight ® controls the motor speed to achieve the fastest 

possible tightening without excessive overshoot. Comparing it 

to a traditional Two Step strategy, TurboTight ® runs faster for 

a longer period.


Two Step 

Speed (rpm) Torque (Nm) 

Speed (rpm) Torque (Nm) 

t 

t 2 . t 

In the examples above you can see that TurboTight ® reaches 

the target torque after the time [ t ]. The Two Step tightening 

strategy takes more than twice the time [2 · t ] to reach the 

target torque. 

As the graph at the top 

shows, with TurboTight ® 

the tool runs fast throughout 

the tightening cycle, 

yet reaches the target 

torque at low speed. 

Thus, the reaction force is 

minimized. 

Final torque 


9

The perfect TurboTight ® partnership 

– the controller is the brain while the 

tool supplies the inertia. 


2.2 How is reaction force reduced? 

TurboTight ® uses the tool’s mass moment of inertia to reduce 

the reaction force transmitted to the operator. The increased 

control of the motor in combination with the fast dynamic 

regulation enables the tool to minimize the reaction force from 

the tightening. 

2.3 How come set-up is so easy? 

TurboTight ® is a strategy that controls the motor speed based 

on the actual torque rate and the remaining torque of the joint. 

Since all these parameters are dynamically calculated during 

the tightening, the only user input required is the target torque. 

2.4 How does TurboTight ® provide energy savings? 

Since 2010 Atlas Copco has been ISO 14001 certified, ensuring 

the planning, execution, control and optimization of continuous 

improvement processes for all Atlas Copco Industrial 

Technique products. 

If we compare the energy consumption of a Power Focus 

4000 running a Tensor ST tool with a Two Step set-up, with 

the energy consumption of a Power Focus 600/6000 running 

a Tensor ES/STR tool with TurboTight ® , we get the following 

result.

Thanks to TurboTight ® energy consumption will decrease 

by 10% due to faster tightening cycles. In general the losses 

during a tightening can be reduced by speeding up the tightening 

phase. But remember the big savings come from standby. 

This pie chart illustrates a “normal” user case 

with a specific tool size and a specific number 

of tightenings/minute. It does not apply in 

all cases. 

32% 

Standby 

Tightening 

Rundown 

8% 

60% 

Energy Consumption = Standby + 

Rundown + Tightening where: 

• Standby represents 60% 

• Rundown represents 32% 

• Tightening represents 8% 

Tools using TurboTight ® make light 

work of tightening. 


10% energy 

savings. 


11

With TurboTight ® there is less heat 

development and the tool is cooler 

and more comfortable to handle. 

Pull a sheet of paper out from under 

a glass of water with a sharp jerk and 

the glass stays on the table. Pull it out 

slowly and it takes the glass with it. 

This can be compared to TurboTight ® , 

where the glass is the tool and the 

hand is the tighten ing cycle. When 

the final torque is reached there is no 

jerk transmitted to the operator since, 

due to the fast tightening speed, the 

weight of the tool absorbs the reaction 

force. 


3 Ergonomics 

3.1 Letting the tool absorb the reaction force 

The force from a handheld tool acting on the operator is called 

the reaction force. The reaction force can be counteracted either 

by the inertia of the tool or by the operator’s muscle force. 

One of the main goals of TurboTight ® was to reduce the reaction 

force force by letting the tool’s inertia absorb most of the 

reaction force. This is achieved by increasing the tightening 

speed. 

The tool inertia’s ability to counteract reaction force depends 

on: 

– Speed of rotating parts during tightening, 

– Inertia of the tool – tool weight, 

– Joint characteristics – a hard joint has a faster torque buildup 

and will be tightened in a shorter time. 

The operator’s ability to counteract the reaction force depends 

on: 

– His/her muscle strength, posture, age and gender, 

– Reaction time. 

There is a time span where the tightening is too slow for the 

inertia to absorb the reaction force or too fast for the operator to 

build up muscle force in a controlled way. A tightening in this 

region will feel jerky and uncomfortable. 

A tool using TurboTight ® should be held less firmly. This will 

improve the ergonomics even further by reducing the static 

load on the operator.

3.2 Less heat development 

Also contributing to good ergonomics, with TurboTight ® , since 

the tool works faster, it does not consume as much energy 

during a tightening cycle. As a result, there is less heat development 

and the tool is cooler and more comfortable to handle. 

When you work with TurboTight ® , 

you can hold the tool in a relaxed 

grip and you don’t need to prepare 

yourself for a jerk caused by the 

torque reaction at the end of the 

tightening. 

With TurboTight ® the tool inertia 

takes the strain by absorbing the 

torque reaction. 

Depending on muscle strength, 

posture, age and gender, the torque 

reaction from a tool can put stress 

on the operator. TurboTight ® enables 

tightening to be performed comfortably 

even in less accessible places, 

such as overhead. 


13

From snug to final torque, Turbo- 

Tight ® ensures a smooth and 

comfortable tightening cycle for the 

operator. 

Soft joint 

Hard joint 

360° 50° 

A soft joint reaches target torque at 

360° and a hard joint at 50°. 

Example of an ergonomic chart for a 

Tensor ETV STR tool. A soft joint has 

weaker ergonomics. 


Torque 

55 

50 

45 

40 

35 

30 

25 

20 

15 

Excellent 

ergonomics 

Please consult our tightening experts to find out if 

TurboTight ® is the optimal tightening strategy for 

your specific application. 

Acceptable 

ergonomics 

10 

0 50 100 150 200 250 300 

Joint angle 

Weak 

ergonomics

4 Accuracy 

When running TurboTight ® the accuracy may decrease compared 

to a moderately tuned Two Step tightening. However 

the tool is still within its accuracy limits. This means for 

Tensor ES ±7.5% over ±3σ, and for Tensor STR ±5.0% over 

±3σ, according to ISO 5393. 

When tightening joints with a stiffness of around 70° 

and below, the speed might need to be reduced due 

to overshooting or inaccuracy problems. This always 

varies with different tool types, surfaces and friction. 

Accuracy 


15

Clamping 

force 

Different types of bolt. The large 

friction radius of a flange screw may 

cause a higher clamp load. 

When tightening fasteners with a 

large friction radius, such as flange 

screws, the coating melts. This causes 

“aquaplaning” under the head, resulting 

in a decrease in friction. 

Example of a customer-specific 

Application Analysis Report. For more 

information, please consult your Atlas 

Copco representative. 


5 Clamp force 

Empirical studies with a selection of bolt types with various 

coatings, e.g., zinc flake or nickel, and without any temperature 

sensitive lubricants, indicates that by using TurboTight ® 

there will not be a difference in clamp force compared to 

traditional tightening strategies such as Two Step. 

Coatings and surface treatments such as wax, grease, paint, 

Teflon, etc., may reduce friction due to increased temperature 

caused by a higher tightening speed. Due to the high tightening 

speed of TurboTight ® , the heat build-up in contact surfaces 

will reduce the friction, enabling higher clamp force. 

If the geometry of the fastener is beneficial, i.e., if the friction 

radius is large, as in flange head screws, the coating melts 

and causes a kind of “aquaplaning” under the head, resulting 

in a decrease in friction. The underhead friction decrease 

will result in a greater tightening angle leading, in turn, to a 

higher clamp force. 

On the other hand, if the friction radius is smaller, as with 

inner hex screws, for example, there is a risk of penetrating 

the coating/surface treatment, which would result in metallic 

contact between the screw and the joint. 

This can cause local welding between the surfaces as a result 

of higher friction. Since more torque is consumed under the 

head due to the higher underhead friction, the clamp force 

will be reduced compared to the same tightening carried out 

at a lower speed. 

ADVANCED FASTENING TECHNOLOGY 

Test parts – bolts and screw joint 

Test equipment 

Seven different bolt types were tested. 30 pcs of each type were available. 

Technical Report 

Type Technical report 

Title TurboTight tests on VW bolts measuring Clamp load and Residual torque 

Prepared By A. Roloff 

Approved By 

Revision 4 Last Modified 2012-11-01 

Summary 

The intention with this investigation was to see if there is a significant difference in achieved Clamp 

load and Residual torque in a screw joint when tightened at different tightening speeds / tightening 

strategies. The question is if the coefficient of friction is affected of the tightening speed and if the 

answer is yes, how? 

Seven different bolts from VW were tested in a test fixture. 

Three different bolt coatings were available: 

b140: No information available 

t647: Zinc-flake with lubricant 

r677: No information available 

- PowerMACS Classic system with a QMX50-15RT was used to create reference tightenings 

results. 

- PowerFocus 6000 system was used with two different tools, one ETV-STR61-50 and one ETV- 

STR61-40. 

- The test joint is built up with a load cell that has an internal “nut” (a threaded part made of 

- MC900 Transient recorder with an IRTT torque hardened angle inline steel). transducer The screw and joints a RS-Technologies 

effective clamp length is built up with steel spacers and the flat 

load cell. 

metal bar (called the under head material) with drilled holes according to standard. See the 

picture below: 

1 2 3 4 5 6 7 

- As a reference, a fixtured QMX nutrunner controlled by a PowerMACS Classic system tightened 5 

bolts in two steps with the speed 200 and 20 rpm. The torque in the first step was set to 20% of the 

final torque. 

- Next, 5 bolts were tightened to the same final torque with an ETV-STR61-50 or ETV-STR61-40 

controlled by a PowerFocus 6000 using the TurboTight strategy (using the Quickprog function). 

- All tests were repeated on three different under head materials. Raw Aluminum anodized Aluminum 

and raw steel. The same threaded hole was used in all tests, 

- The relation between tightening torque, Clamp load and residual torque varies almost +/- 10% for 

these combinations of bolt types, bolt coating, under head material and tightening method/speed. 

See Table 4: The measured results are first recalculated to the same tightening torque level and then 

the quotes for Clamp load, Residual torque and Residual Torque/Load between the QMX and the 

STR are calculated. 

- No significant difference in Clamp load or Residual torque could be seen in the results that 

could be explained by a speed dependant friction coefficient. 

NOTE: The bad results in the two points below are probably explained by the use of a “High 

noise tool”. The ETV-STR61-50 that was used was of the old version that had some problems 

with electrical noise in the torque transducer signal. The intention with this investigation was 

not to evaluate the torque scatter from the STR machine and therefore it hasn’t a major 

influence on the Clamp load and the Residual torque comparisons. 

- A torque “overshoot” with up to 20% could be noted with the ETV-STR tests and the torque scatter 

was significantly higher compared with the QMX tests. The torque scatter is based on 5 values which 

makes the absolute results very uncertain. 

- Another observation was that the average torque and the torque scatter measured with the inline 

reference transducer were lower than reported from the PowerFocus 6000. 

TurboTight tests on VW bolts_4.doc Page 2 of 15 



TurboTight tests on VW bolts_4.doc Page 4 of 15

The TurboTight ® strategy is not suitable for applications 

where Torque-Angle strategies should be chosen to deliver 

an accurate clamp load. Some customer requests might need 

a thorough joint analysis to assure the optimum tightening 

parameters. 

Please keep in mind the possible risk of high speed 

tightenings like TurboTight ® affecting the clamp load 

value to the bolt for a certain torque value (as given 

in recommendations from screw manufacturers and 

standardization committees). There may be a risk of 

tightening the screw beyond yield. 

If you need to investigate the clamp load status of a bolt, 

please contact Atlas Copco for more information. 

Fasteners such as inner hex screws 

have a smaller friction radius. Thus, 

there may be higher friction leading 

to higher temperature under the 

head, which could cause a decrease 

in clamp force. 

The impact of the size of the friction 

radius of different fasteners on the 

heat generated during tightening 

can be compared to different sized 

frying pans. There is a faster build-up 

of heat in a small frying pan. In the 

large pan the heat is dissipated over 

a larger area. 


17

When the joint surface is magnified, 

ridges and hollows become visible. 


6 Relaxation 

When the surface of the joint is magnified, what appears to be 

a smooth surface actually consists of ridges (or asperities) and 

hollows. Partial plastic collapse (embedding or settlement) of 

the surface results in a preload loss or relaxation. This preload 

loss is time dependent but occurs over a very short time and 

can be measured in milliseconds. 

If the tightening occurs over a short period of time, the preload 

loss will be greater compared with if the tightening occurs 

over a longer period of time. For TurboTight ® some relaxation 

has been observed and the higher the speed the more relaxation 

can occur. 

However, the relaxation observed from experiments shows 

that, comparing TurboTight® with a Two Step tightening 

strategy, the relaxation of the clamp load will increase by less 

than 4%. 

7 Residual Torque 

Tests with a selection of bolts have not shown any significant 

difference in the clamp load or the residual torque by using 

the TurboTight ® strategy. The bolts were surface treated with 

coatings such as zinc flake or nickel and the bolt surface was 

not waxed, oiled or coated with grease or any other lubricant. 

In some cases, with bolts with a small friction radius, such as 

inner hex bolts, measurements have shown that the residual 

torque can increase by up to 20%. 

The reason for the residual torque increase is that as the contact 

surface cools down, the coefficient of friction increases. 

There may be local miniature welding in areas where the 

temperature during rundown was high due to the increased 

friction. The miniature welding will increase the residual 

torque – the weld has to be cracked.

8 Torque scatter 

In some applications a small increase in torque scatter 

has been noted. In particular, very hard joints cause 

higher torque values or torque overshoots. This is 

because the tool needs a minimum time of 12 ms 

between the snug level and the final torque to be able 

to regulate in order to deliver accurate torque. 

9 Where to use TurboTight ® 

TurboTight ® can be used where higher cycle speed is required. 

In some cases, it can be used to improve operator ergonomics, 

although the tightening of “softer” joints will have a tendency 

to feel slightly more jerky. It is always advisable to test the 

behavior of the tool in real customer applications. 


TurboTight ® is the optimal tightening strategy for your 

specific application. 

The tool needs a minimum of 12 ms 

between the snug level and the final 

torque to be able to regulate in order 

to deliver accurate torque. 

When using TurboTight ® on a soft 

joint the reaction force is greater than 

with a hard joint and the tightening 

may feel slightly jerky. 


19

It pays to use the right tool for the 

job. If you use, for instance, a 70 Nm 

tool on a 35 Nm joint, the result will 

be less ergonomic behaviour. The correct 

choice would be a 40 Nm tool. 

What should you focus on when 

choosing a tool? Optimize your tightening 

operations by choosing the tool 

with maximum torque closest to your 

application torque. 


10 Recommendations 

relating to TurboTight ® 

As a rule of thumb and as explained in the previous 

chapters, TurboTight ® is optimal for joints exhibiting 

a joint stiffness between 70° and 270°, depending on 

tool size. See graph on page 14. 

When choosing a tool with TurboTight ® the size and speed of 

the tool and the joint stiffness will affect the performance. A 

higher tool speed will create a feeling of a joint being harder. 

Ideally Tensor ES/STR tools will work best close to the maximum 

recommended tool torque. 

Customer tool recommendation example 

A joint with a stiffness of 120° and a specified torque of 

35 Nm should be tightened with TurboTight ® to obtain the 

main benefits of improved productivity and ergonomics. 

Given Looked for 

Joint stiffness = 120° Angle tool needed 

Final torque = 35 Nm ± 2 Nm Tool size = ?

Use of an over dimensioned tool 

An over dimensioned tool may deliver a bigger spread in 

overall accuracy in the application. Tools with a higher torque 

range than the torque required for TurboTight ® have a bigger 

spread because the torque reading takes place in the lower area 

of the torque transducer’s reading range. Using the tools in the 

lower torque area will always increase the torque scatter. 

10.1 TurboTight ® and tool extensions 

When a tool extension or any other accessory is used between 

the tool and the socket it can cause a decrease in torque accuracy. 

Tests conducted by Atlas Copco show a small decrease in 

accuracy when the target torque is close to the tool’s maximum 

torque. Torques in the lower region of the tool’s torque range 

show a greater decrease in accuracy. 

If the use of an extension or any other accessory cannot be 

avoided, apply the following rules: 

1. The accessories should be as stiff as possible, e.g., thick, 

short extensions are better than long, slim ones. 

2. If possible, use supported accessories, e.g., extensions with 

ball bearings. 

3. Use the tool close to its maximum torque. 

10.2 The limitations of TurboTight ® 

Since TurboTight ® calculates at which point the tool has to be 

stopped and as even the fastest possible sampling rate between 

the controller and the tool will have limitations, TurboTight ® 

will not be suitable for all joints. 

On very soft joints with more than 270° joint stiffness 

the tool will still be unable to deliver optimal ergonomic 

results, since the soft joint condition will increase 

tightening time, thus increasing the reaction force to 

the operator. 

On hard joints of less than 70° the tool may have 

insufficient time to find the torque rate and to regulate 

the motor to the requested torque level. The result will 

be an overshoot. TurboTight ® needs at least 12 ms 

between the snug torque level and the final torque 

level. 


21

T (Nm) 

Tensor ETV STR. 

Joint 2 Joint 3 

Joint 1 

Angle 

(degrees) 

Joints 1 and 2 have the same k factor 

but different target torques. Joints 2 

and 3 have the same target torque 

but different k factors. Joint 3’s k 

factor is half that of joint 2. 

Tensor ETV ES. 


TurboTight ® was designed to be used for torque tightenings. 

TurboTight ® cannot be used in tightenings where bolts have 

to be tightened to a certain angle. 

Other components, such as washers, O-rings, etc., will 

distort the k factor of a joint (torque rate), leading to 

a wide variation in the k factor during one tightening 

sequence. Thus, suddenly the k factor will no longer be 

linear. This will cause misbehavior of the TurboTight ® 

algorithm, resulting in incorrect target torque values. 

TurboTight ® only works with Tensor ES and Tensor STR 

tools operated by Power Focus 600 or 6000 controllers. 

Using a Tensor STR tool with a Power Focus 4000 

will not allow the use of Tensor STR tools with Turbo- 

Tight ® (see Table 1 below). 

Hard joints and soft joints 

Joint “hardness” is defined in figures as the “torque rate”, i.e., 

the tightening angle necessary to achieve the recommended 

torque, measured from the snug level. The torque rate can 

vary considerably for the same diameter of screw. A short 

screw clamping plane metal components reaches the rated 

torque in only a fraction of a turn of the screw. This type of 

joint is a “hard joint”. 

A joint with a long screw that has to compress soft components 

such as gaskets or spring washers can require several 

turns of the screw or nut to reach the rated torque. This is a 

soft joint. The two different types of joints behave differently 

when it comes to the tightening process. 

System combinations allowing the use of TurboTight ® 

TurboTight ® PF 600 PF 6000 

Tensor ES OK – 

Tensor ST – – 

Tensor STR – OK 

Tensor STB – – 

Tensor DS – – 

Tensor SL – – 

Table 1.

Always consider a joint failure 

or a tool error which can cause a 

sudden unexpected reaction force 

and possibly injure the operator. 

Please consult our tightening 

experts to find out if TurboTight ® 

is the optimal tightening strategy 

for your specific application. 

TurboTight ® and safety 

Please remember to avoid using TurboTight ® in applications 

outside its limitations (see pages 24 and 25). 

Atlas Copco recommends using TurboTight ® within 

the same torque limits as for other, slower tightening 

strategies. 

10.3 How to set up TurboTight ® 

It is very easy to set up TurboTight ® . Use the 

Power Focus 600/6000 controller with the 

TurboTight ® quick programing function. 

The quick programing will be suitable for most 

joints selected. However there might be cases where 

TurboTight ® delivers lower residual torque values or 

torque overshoot. 

If the auto set-up does not deliver suitable residual torque 

results, the following steps are recommended: 

TurboTight ® set-up with 

Power Focus 600. 

TurboTight ® set-up with 

Power Focus 6000. 

Power Focus 600 and Tensor ES. 


23

Due to its shape, the spring washer 

slows down the last part of the 

tighten ing cycle until the washer 

flattens out with a jerk. From this 

point the final part of the tightening 

takes place at high speed. The jerk is 

reflected as a peak or “knee” in the 

graph below. 

Torque 

Snug 

Knee 


t 

What to do if residual torque is too high 

1. Look at the bolt coating to determine if it could influence 

the torque overshoot. 

2. Determine if additional joint components, such as gaskets, 

sealings, glue, etc., are used with the joint. 

3. Tighten with the tool used previously and measure the 

residual torque with an STwrench. Note the residual torque 

value. 

4. Tighten with a Tensor ES or Tensor STR tool using Turbo- 

Tight ® and measure the residual torque with an STwrench. 

5. Compare the residual torque check value from the tool used 

in step 3 with the residual torque check from the Tensor ES 

or Tensor STR tool. 

6. TurboTight ® works best with tightenings with a fairly linear 

torque rate. If a knee should occur close to snug level, try to 

increase the “rundown complete” level to above the knee. If 

possible, look at the torque traces over time and analyze the 

torque increase. 

7. Since the friction in a joint might have changed towards a 

lower friction coefficient, adjust the target torque accordingly 

to reach the needed clamp force. This always has to be 

agreed with the customer. 

8. If specific investigations are required, please contact your 

local Atlas Copco representative or Atlas Copco SEPO.

Table of influences 

Coatings or components Observations Result 

Wax Melts with high speed tightening Less friction under the head or in the 

threads, causing higher clamp force 

Oil Might burn away, which causes 

higher friction 

Grease Might burn away, which causes 

higher friction 

Table 2. 

Causing less friction or higher friction, 

causing higher or lower clamp load 

Causing less friction or higher friction, 

causing higher or lower clamp load 

Teflon Lower bolt friction coefficient Causing less friction 

Paint or lace Lower surface friction coefficient Causing less friction and causing 

relaxation after high speed tightenings 

Gaskets Element which softens joints Will relax after a high speed tightening 

has been performed 

Seals Element which softens joints Will relax after a high speed tightening 


Viscose glue Element which softens joints Will relax after a high speed tightening 


Adhesives Element which softens joints Will relax after a high speed tightening 


In the case of torque overshoot with hard joints 

Look at the snug torque. If it is set too high, reduce the snug 

torque assuring that the prevailing torque of the joint is still 

below the snug torque. The snug torque is expressed by 

the torque parameter when rundown is complete within the 

TurboTight ® set-up. 

If the tool still delivers torque value overshoots, take the 

following action: 

• Manually reduce the tightening speed in steps to reach 

accepted torque values, 

• Reduce the speed manually in steps and check the torque 

rate. When you have reached an acceptable level of torque 

accuracy you have reached the maximum possible Turbo- 

Tight ® tightening speed. 

In some cases the joints are so hard that the tightening speed 

has to be reduced to below 50% of the maximum possible 

tight ening speed. A lower speed might cause the tool to 

transmit a jerky feeling to the operator, thus reducing operator 

comfort. In this case TurboTight ® should not be used. 

Remember that more samples will 

deliver a better statistical result. 


25

To ensure customer satisfaction, 

the customer and Atlas Copco must 

agree on using TurboTight ® in a 



To verify the consistency of joints please check in advance the 

residual torque of the bolt which has been tightened with the 

tool previously used in the application. 

After tightening with a Tensor ES or Tensor STR tool check 

the residual torque again and verify that the torque variation 

levels do not differ excessively from the values produced with 

the old tool. Variations of ±10% should still be considered as 

ok values. 

In the case of unacceptable ergonomic behavior 

on soft joints 

Increase the TurboTight ® tightening speed as much as possible. 

If the tool behavior is still not acceptable ergonomically, 

TurboTight ® cannot be used in the application. Use a Two Step 

tightening strategy instead, or torque arms or other reaction 

devices. 

10.4 TurboTight ® and the customer 


TurboTight ® is the optimal tightening strategy for your 


If you need support, please contact your local Atlas Copco 

Tools representative.

10.5 FAQs – Frequently Asked Questions 

No. Question Answer 

1 Can TurboTight ® be used together with a 

software safety function? 

2 What is the torque accuracy for Tensor ES 

tools using TurboTight ® ? 

3 What is the torque accuracy for Tensor STR 

tools using TurboTight ® ? 

4 Why can TurboTight ® be used with Tensor 

ES and Tensor STR tools? 

5 What limitation does TurboTight ® have on 

hard joints? 

6 What are the main benefits of using 

TurboTight ® ? 

7 Which surface treatments will influence 

the clamp force of joints, tightened with 


8 Will TurboTight ® have an influence on the 

relaxation of tightened joints? 

9 Can TurboTight ® be used with Tensor STR 

using Power Focus 4000? 

10 Can Tensor ST tools be retrofitted with 


11 Is there a rule-of-thumb regarding which 

joints TurboTight ® should be used on? 

12 Should TurboTight ® be verified on the actual 

joint if there are doubts about clamp force 

and ergonomic performance? 

*) This is valid for a correct TurboTight® set up 

There is no software safety function available 

for TurboTight ® . 

±7.5% over ±3σ *) 

±5.0% over ±3σ *) 

Because of the higher sampling rate between 

the controller and the tool. 

From snug to final torque there must be a 

minimum of 12 ms for TurboTight ® to function 

properly. 

Reduced cycle time, reduced reaction force, 

easy to set up, energy savings 

Coatings and surface treatments like wax, 

grease, paint, Teflon, etc. 

Yes, there might be a slight increase, since 

there is no stop time during the tightening 

sequence being carried out. 

No, since the Power Focus 4000 controller cannot 

support a high sampling rate. 

No, since Tensor ST tools cannot handle the 

required sampling rate. 

As a rough rule-of-thumb, joints should have a 

stiffness of around 70 to 270 deg. 

Please follow the advice in the Pocket Guide. 

Final judgement lies with the customer, and 

we should be clear about the characteristics 

of TurboTight ® . 


27

www.atlascopco.com 

9833 1994 01 Recyclable paper. Jetlag/Boardwalk 2013:1. TR Tryck 2013. 

© Atlas Copco Industrial Technique AB. All rights reserved. No part of this publication may be reproduced without the prior permission of the copyright holder.

Atlas_Copco_Pocket Guide_TurboTight_UK__.pdf - Atlas Copco

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