Q&A   Locking Device

The following is the list of answers for frequently asked questions from our customers. Click the question and see the answer.

Under consideration

About design

Q1 Can we use the Power-Lock for a shaft on which a keyway has been machined already?
Q2 Can the Power-Lock accept bending moments?
Q3 Our shaft is a little short and the Power-Lock protrudes from the shaft end. Can we use them?
Q4 What is the allowable limit for the surface roughness of the shaft and hub with which the Power-Lock makes contact?  
Q5 Are there any problems with using a Power-Lock for a hollow shaft?
Q6 There is a note stating "A safety factor is not included." for the hub diameter list in the catalog. What safety factor is required?
Q7 How much will the centering accuracy be when the Power-Lock series without the centering function is used with a hub without a guide?
Q8 We want to use several Power-Locks together because the torque is insufficient with a single Power-Lock. How much transmission torque is expected in this case?
Q9 Can we use the Power-Lock for applications subject to large impact load, such as presses or construction machinery?
Q10 Although the Power-Lock catalog says "in principle, the Power-Lock cannot accept bending moments," what actually happens when moments act on the Power-Lock?
Q11 For the KE Series Power-Lock, straight bores are allowed thanks to the KE Series centering functions. However, the list of hub diameters shows hubs with a guide. Are there any situations where it's better to install a guide?
Q12 I am considering using the KE Series, but outer diameters of hubs are insufficient. Is there a way to solve this problem? The torque has enough capacity.
Q13 The instruction manual for the AS-SS Series says "applying oil or grease will reduce the torque." Applying oil to a series that requires lubrication doesn't cause slip, so why does lubricant decrease the torque of the SS Series?
Q14 How can I calculate the minimum hub diameter for the AS Series whose the hub diameter B is less than 2ℓ?
Q15 When selecting the AD-N Series without a guide, should the hub length be more than Lt in hub diameter table (2)? Is there any problem if it exceeds L?
Q16 It looks like there is a gap between the AD-N Series Power-Lock and the hub in diagrams showing mounting of the Power-Lock to the hub (when installing with a guide) in the catalog. Is this gap necessary? Will I have problems if the Power-Lock is installed without a gap?
Q17 Why is there a difference in the transmission torque between RE-SS Series Power-Locks with a retaining ring and those without a retaining ring?
Q18 Can we use the Power-Lock when the hub width is shorter than the Power-Lock width?
Q19 Can the EL Series accept radial loads? This series is not shown in the allowable surface pressure table in the selection guide section of the catalog.

Ambient environments

Q21 We installed the Power-Lock in a room temperature environment, but we decided to use it in a location where the temperature is about 180°C. The temperature difference is significant. Are there any problems such as degradation of the transmission torque?
Q22 Is it possible to use the stainless steel Power-Lock under the sea?  
Q23 Can we apply Raydent coating to the Power-Lock? (Use in a clean room)
Q24 Will there be a problem if I use the Power-Lock with oil bath lubrication?

After deciding to use the Power-Locks

About design

Q20 Can we use the TF series without a spacer?

Instructions

Q25 What happens when the Power-Lock is assembled without using a torque wrench?
Q26 What happens when the bolts are tightened with a torque less than the specification?
Q27 To what areas do we need to apply oil or grease during mounting?
Q28 What happens when a series which requires the application of oil/grease to the tightening bolts during assembly is assembled in a dry state without the application?
Q29 Can we use washers for the tightening bolts to prevent loosening?
Q30 What in particular should we be careful about when handling the AD-N series?
Q31 I will use the AD-N Series Power-Lock. How do I apply lubricant, especially during assembly?
Q32 I will use the TF Series Power-Lock. What are its features and how do I handle it?
Q33 I will use the EF Series Power-Lock. What are its features and how do I handle it?

When using the Power-Locks

Instructions

Q34 How many times can we repeat the mounting and removal of the Power-Lock?
Q35 Is it possible to reuse a slipped Power-Lock?
Q36 Is there any possibility that the bolts of the Power-Lock will come loose?  
Q37 Should I regularly check whether the locking bolts are completely tightened by using a torque wrench? Will checking them break the bolts?
Q38 When removing the AD-N Series Power-Lock, why do you grease to the threads?

Others

Q39 Can I purchase only locking bolts for the Power-Lock unit?
Q40 I currently use the PL035X060 model, but the model no. changed to PL035X060AS. Is there any difference between the two? Also, can PL035X060AS replace PL035X060 as is?
Q41 I currently use the PL045X075AD model, but the model no. changed to PL045X075AD-N. Is there any difference between the two? Also, can PL045X075AD-N replace PL045X075AD as is?
 Answers
Q1 Can we use the Power-Lock for a shaft on which a keyway has been machined already?
A1

Although the transmission torque and thrust load will decrease to 90% of the values in the catalog, you can use it. Note that there is one exception. You cannot use the EL series for the shaft with a keyway because the main body may deform and this may disable the removal.

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Q2 Can the Power-Lock accept bending moments?
A2

In principle, the Power-Lock cannot accept bending moments. Contact us if the lock will be subject to bending moments similar to those shown in the figure on the right.

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Q3 Our shaft is a little short and the Power-Lock protrudes from the shaft end. Can we use them?
A3

No, you can't use it because a shorter shaft may cause uneven distribution of force to the inner ring and other parts, resulting in the deformation of the Power-Lock. The centering accuracy also decreases due to the deformation.  

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Q4 What is the allowable limit for the surface roughness of the shaft and hub with which the Power-Lock makes contact?  
A4

The following values described in the catalog shall be the allowable limit and machining rougher than the values is not allowed. When a surface pressure is applied on the surface of the shaft and hub, it is expected that the irregularities on the surface are flattened out by the pressure, resulting in the plastic deformation of the shaft and hub. As a result, the outer diameter of the shaft becomes smaller and the inner diameter of the hub becomes larger by the amount of the surface roughness, resulting in the decrease of the transmission torque. The plastic deformation may become larger due to the change over time.

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Q5 Are there any problems with using a Power-Lock for a hollow shaft?
A5

When using a hollow shaft, you need to consider its material and inner diameter to determine whether the strength of the shaft is sufficient for the surface pressure on the shaft generated from the tightening of the Power-Lock. Refer to the catalog data for details including the calculation formula.

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Q6 There is a note stating "A safety factor is not included." for the hub diameter list in the catalog. What safety factor is required?
A6

The list in the catalog shows the minimum outer diameters for the hubs to withstand the surface pressure applied on the inner diameter surface of the hub when the bolt is tightened with the specified tightening torque (MA). The generated surface pressure varies depending on the tightening torque. Assuming the error for a typical torque wrench is ±5%, we recommend a safety factor of at least 10%.

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Q7 How much will the centering accuracy be when the Power-Lock series without the centering function is used with a hub without a guide?
A7

It is certain that the deviation will be quite large and the value is unpredictable. Consequently, such usage is not allowed. Be sure to provide a centering guide for the hub. Setting the length of the centering guide to half of the shaft diameter (d/2) or more ensures practical centering accuracy. Determine the tolerance of the guide according to the required accuracy.

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Q8 We want to use several Power-Locks together because the torque is insufficient with a single Power-Lock. How much transmission torque is expected in this case?
A8

Although the transmission torque increases, the scaling factor varies depending on the series. Note that some series are not applicable for the application to use several Power-Locks together.  

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Q9 Can we use the Power-Lock for applications subject to large impact load, such as presses or construction machinery?
A9

Even when impact load is applied repeatedly, the Power-Lock provides sufficient ability as long as you determine the safety factor carefully and maintain the bolt tightening torque properly. As a guideline, the safety factor (S.F.) for the impact torque is 5 or more.

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Q10 Although the Power-Lock catalog says "in principle, the Power-Lock cannot accept bending moments," what actually happens when moments act on the Power-Lock?
A10

The Power-Lock uniformly applies surface pressure on the shaft and hub along the entire circumference for friction locking.
A large bending moment will cause the shaft or hub to lean into the Power Lock.
This may cause non-uniformity or increased surface pressure. In addition, the Power-Lock, shafts, and hubs may suffer plastic deformation and become unusable.

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Q11 For the KE Series Power-Lock, straight bores are allowed thanks to the KE Series centering functions. However, the list of hub diameters shows hubs with a guide. Are there any situations where it's better to install a guide?
A11

There are three benefits to installing a guide:
1. Can reduce vibration on the hub side depending on the gap between the shaft and guide.
2. Can reduce the hub diameter.
3. Hubs with guides make actual work easier (easy Power-Lock installation).

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Q12 I am considering using the KE Series, but outer diameters of hubs are insufficient. Is there a way to solve this problem? The torque has enough capacity.
A12

Please consider using the KE-LP Series. Hub diameters can be downsized thanks to its low surface pressure. Contact a Tsubaki representative for more information.

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Q13 The instruction manual for the AS-SS Series says "applying oil or grease will reduce the torque." Applying oil to a series that requires lubrication doesn't cause slip, so why does lubricant decrease the torque of the SS Series?
A13

Lubrication with decrease the coefficient of friction on both of the standard series (requires lubrication) and the stainless steel series (requires no lubrication).
The standard series is designed based on the assumption of a low coefficient of friction coefficient, while the stainless steel series is designed for a high coefficient of friction. Therefore, the coefficient of friction between the Power-Lock, shafts, and hubs will decrease if you apply oil to the stainless steel series, thereby resulting in decreased torque.

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Q14 How can I calculate the minimum hub diameter for the AS Series whose the hub diameter B is less than 2ℓ?
A14

When hub width B is ℓ<B<2ℓ, calculate the hub configuration coefficient K3 as 1.0.
Note, however, to be sure to install a guide.

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Q15 When selecting the AD-N Series without a guide, should the hub length be more than Lt in hub diameter table (2)? Is there any problem if it exceeds L?
A15

This should not pose a problem if the hub length exceeds L. However, the bolt head will protrude.

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Q16 It looks like there is a gap between the AD-N Series Power-Lock and the hub in diagrams showing mounting of the Power-Lock to the hub (when installing with a guide) in the catalog. Is this gap necessary? Will I have problems if the Power-Lock is installed without a gap?
A16

This should not pose a problem if the Power-Lock touches the back of the hub in its pre-assembled state. The taper rings will move when you tighten the locking bolts during installation, and so there will be gaps deep in the bore.
However, avoid moving the Power-Lock to the back when tightening bolts. The taper rings will not move and the Power-Lock will not come out.

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Q17 Why is there a difference in the transmission torque between RE-SS Series Power-Locks with a retaining ring and those without a retaining ring?
A17

Retaining rings act as flanges for Power-Locks and reduce hub travel when tightening.
By minimizing this hub movement, part of the axial face generated on the bolt will be lost as friction loss on the outer ring and boss sliding surface. This will ensure that there will be less torque on Power-Locks with retaining rings than on those without.

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Q18 Can we use the Power-Lock when the hub width is shorter than the Power-Lock width?
A18

Only the ML series can be used. Since the surface pressure applied on the hub will increase, use the following equation to obtain P'k, or the surface pressure on the hub, and confirm that the strength of the hub material and the necessary hub outer diameter are satisfied.

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Q19 Can the EL Series accept radial loads? This series is not shown in the allowable surface pressure table in the selection guide section of the catalog.
A19

The EL Series can be used if Prad/P is less than 10% in the allowable surface pressure table. The surface pressure on the shaft side/hub side differs depending on the customers' specifications (bolt size, number required, locking torque, etc.).

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Q20 Can we use the TF series without a spacer?
A20

No, you can't use it without a spacer because of the following reasons:  (1) The inner ring will deform. (2) The tightening bolts will interfere with the hub. (3) The hub mounting position cannot be fixed. (4) The hub moves during assembly.  

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Q21 We installed the Power-Lock in a room temperature environment, but we decided to use it in a location where the temperature is about 180°C. The temperature difference is significant. Are there any problems such as degradation of the transmission torque?
A21

When the materials used for the shaft and hub are the steel type equivalent to the Power-Lock, there is no problem because the shaft, Power-Lock, and hub expand together. If the materials are different, such as stainless steel or aluminum, additional consideration is required. Contact us for more information. Note that the allowable ambient temperature is between -30°C and +200°C.

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Q22 Is it possible to use the stainless steel Power-Lock under the sea?  
A22

If the generation of some rust does not present a problem for the application, it can be used in this way. Even when the Power-Lock is used in water, little water enters the inside due to the high pressure on the mounting contact surface; therefore, performance is not affected. If no rust is allowed for the application, the Power-Lock cannot be used under the sea.

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Q23 Can we apply Raydent coating to the Power-Lock? (Use in a clean room)
A23

Raydent coating is not allowed because the taper surface becomes rough from peeling, resulting in a lower transmission torque. Consider the use of the electroless nickel-plated types (AS-KP, KE-KP or TF-KP) or stainless steel types (AS-SS, KE-SS or RE-SS).

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Q24 Will there be a problem if I use the Power-Lock with oil bath lubrication?
A24

This should not pose a problem if oil is added after tightening the Power-Lock. However, avoid reusing oil/grease that contains silicon/molybdenum-based anti-friction agents or extreme pressure additives.
If such oil/grease is reused, the coefficient of friction will significantly decrease, which may cause damage to the tightening bolts.

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Q25 What happens when the Power-Lock is assembled without using a torque wrench?
A25

The transmission torque and thrust load in the catalog are the values when the Power-Lock is properly assembled using the specified tightening torque. When a torque wrench is not used for tightening, the specified axial force may not be obtained resulting in the slip of the Power-Lock, the bolt may be damaged, or the Power-Lock body may deform due to excessive tightening. Be sure to use a torque wrench and assemble the lock with the specified tightening torque.

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Q26 What happens when the bolts are tightened with a torque less than the specification?
A26

The bolt tightening torque and the transmission torque of the Power-Lock have a proportionate relationship. Consequently, a lower tightening torque results in a lower transmission torque. It is not recommended to use the Power-Lock with a lower tightening torque because it may lead to bolt loosening.

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Q27 To what areas do we need to apply oil or grease during mounting?
A27

You need to apply oil/grease to the contact surface between the shaft and hub, the contact surfaces between parts such as the taper ring and inner/outer rings, the seating surfaces of the tightening bolts, and the screw surface. Some people think that oil application to the taper surface will cause a slip, however, a lubrication effect is important to ensure the smooth movement of the taper surface during assembly. Note that oils and greases containing molybdenum anti-friction agent should not be used. Also, avoid those containing extreme-pressure agent as much as possible. If such oil/grease is used, the friction coefficient significantly decreases, which may cause damage to the tightening bolts.

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Q28 What happens when a series which requires the application of oil/grease to the tightening bolts during assembly is assembled in a dry state without the application?
A28

If the bolts are tightened without oil/grease, the transmission torque may decrease by 20% or more. Moreover, the tightening bolts might come loose due to vibration. The transmission torque in the catalog was calculated based on the axial force when the bolts are tightened with proper lubrication. Consequently, never attempt to remove oil/grease. Note, however, that the tightening bolts of the ML and SL series and the stainless steel and electroless nickel-plated types of each series have been coated with special lubrication so that no additional oil or grease is necessary during assembly.

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Q29 Can we use washers for the tightening bolts to prevent loosening?
A29

No, you can't. When the Power-Lock is mounted properly, there is no worry about loosening the tightening bolts. Using a spring type or other washer which generates a reaction force decreases the tightening force, resulting in a lower axial force and a lower transmission torque.

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Q30 What in particular should we be careful about when handling the AD-N series?
A30

When compared with other series, the AD-N series has adopted a smaller taper angle to provide a greater transmission torque. Consequently, you need to tighten the bolts little by little, using extra caution during mounting and removal. Quick tightening of the bolts may damage the bolts or screw holes. Be sure to tighten the bolts evenly and a little at a time. (As a guideline, limit the angle of each tightening to 30 degrees.) Also during removal, be sure to use all draw holes and follow the steps described in the instruction manual.

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Q31 I will use the AD-N Series Power-Lock. How do I apply lubricant, especially during assembly?
A31

Visit our website for a video on handling the AD-N Series Power-Lock.
パワーロックAD-Nシリーズ取扱方法

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Q32 I will use the TF Series Power-Lock. What are its features and how do I handle it?
A32

Visit our website for a video on features and handling of TF Series Power-Lock.
パワーロックTFシリーズ取扱方法

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Q33 I will use the EF Series Power-Lock. What are its features and how do I handle it?
A33

Visit our website for a video on features and handling of EF Series Power-Lock.
パワーロックEFシリーズ取扱方法

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Q34 How many times can we repeat the mounting and removal of the Power-Lock?
A34

With the exception of the AD-N series, about 10 times of reuse is possible as long as the Power-Lock has not slipped and has no deformation or flaws. The AD-N series can be reused about two times because it deforms easily due to its structure. When reusing the Power-Lock, follow the same procedure as mounting a new product. The transmission torque of the Power-Lock does not change. For the product with coated tightening bolts, replace the bolts with new ones as necessary. (Send your order to us via your dealer.)

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Q35 Is it possible to reuse a slipped Power-Lock?
A35

Yes, it is possible after you disassemble the lock completely and confirm that no deformation or flaw is found in the parts. You can reassemble it according to the instruction manual. Since the AD-N series cannot be disassembled, observe the entire appearance carefully. In any case, problems such as deteriorated surface roughness can be expected. Limit the reuse to one or two times at most.

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Q36 Is there any possibility that the bolts of the Power-Lock will come loose?  
A36

There is no worry about loosening when the bolts were tightened properly with the specified tightening torque (MA), because their friction torque is greater than the torque of spontaneous loosening. Moreover, (1) The bolts are designed to be used with a high tightening force all the time in order to obtain a friction force used to prevent loosening, and (2) The sections which make contact with the seating surfaces of the bolts are heat-treated to lessen the dent in the seating surface. For the reasons above, the bolts never come loose and you can use the lock reliably.

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Q37 Should I regularly check whether the locking bolts are completely tightened by using a torque wrench? Will checking them break the bolts?
A37

Checking whether locking bolts are completely tightened should not pose a problem. The bolts will not break as long as they haven't rusted, providing you check them with a torque wrench set to the specified values.

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Q38 When removing the AD-N Series Power-Lock, why do you grease to the threads?
A38

We grease to prevent baking or galling of the threads. However, avoid reusing lubrication that contains extreme pressure additives or molybdenum-based anti-friction agents. The coefficient of friction will greatly decrease if such lubricants are used, which may cause damage to the bolts.

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Q39 Can I purchase only locking bolts for the Power-Lock unit?
A39

Yes, you can purchase only locking bolts. Request a quote for the number required, indicating Locking bolts for Power-Locks with the model number of the Power-Lock.

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Q40 I currently use the PL035X060 model, but the model no. changed to PL035X060AS. Is there any difference between the two? Also, can PL035X060AS replace PL035X060 as is?
A40

Power-Locks PL035X060 and PL035X060AS are the same specifications. Only the model numbers have changed. There's no change to dimensions, etc., but we changed some specifications such as locking bolts, transmission torque, thrust load, and surface pressure on the shaft/hub based on a March 2012 review.

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Q41 I currently use the PL045X075AD model, but the model no. changed to PL045X075AD-N. Is there any difference between the two? Also, can PL045X075AD-N replace PL045X075AD as is?
A41

Power-Lock PL045X075AD is compatible with PL045X075AD-N in performance, with only slight dimensional changes. The internal structure PL045X075AD-N was improved, making it easier to remove than the previous AD Series. Therefore, the AD-N Series can replace the AD Series.

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