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.
About handling/surrounding environment
|Q1||Can we use the Power-Lock for a shaft on which a keyway has been machined already?|
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.Back to questions
|Q2||Can the Power-Lock accept bending moments?|
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?|
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?|
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?|
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.
|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?|
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%.Back to questions
|Q7||Can we use the Power-Lock when the hub width is shorter than the Power-Lock width?|
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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|Q8||How much will the centering accuracy be when the Power-Lock series without the centering function is used with a hub without a guide?|
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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|Q9||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?|
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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|Q10||Can we use the Power-Lock for applications subject to large impact load, such as presses or construction machinery?|
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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|Q11||Can we use the TF series without a spacer?|
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.Back to questions
|Q12||What happens when the Power-Lock is assembled without using a torque wrench?|
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.Back to questions
|Q13||What happens when the bolts are tightened with a torque less than the specification?|
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.Back to questions
|Q14||To what areas do we need to apply oil or grease during mounting?|
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.Back to questions
|Q15||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?|
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.Back to questions
|Q16||How many times can we repeat the mounting and removal of the Power-Lock?|
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.)Back to questions
|Q17||Is it possible to reuse a slipped Power-Lock?|
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.Back to questions
|Q18||Is there any possibility that the bolts of the Power-Lock will come loose?|
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.Back to questions
|Q19||Can we use washers for the tightening bolts to prevent loosening?|
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.Back to questions
|Q20||What in particular should we be careful about when handling the AD-N series?|
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.Back to questions
|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?|
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.Back to questions
|Q22||Is it possible to use the stainless steel Power-Lock under the sea?|
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.Back to questions
|Q23||Can we apply Raydent coating to the Power-Lock? (Use in a clean room)|
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).