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FAQ'S

Keyless Transmission Elements
(Locking Assemblies & Shrink Discs)

1) What are locking assemblies?

Devices that positively connect two or more parts to shaft and hub which allow motion to be transmitted and to withstand an axial thrust.

2) Can the locking assemblies be used with a shaft that already has a finished keyway?

Transmissible torque and thrust will decrease by 10% of the catalogue value, but it is possible to use it. However, the N8006 series cannot be used with a shaft that has a finished keyway because it would become impossible to remove N8006 units due to deformation.

3) Can NMTG Locking Assemblies be customized?

Yes. NMTG has the ability to manufacture a variety of custom made products. To meet your specific needs, our experienced engineers offer customized design to optimize application performance. NMTG is recognized throughout the industry for its capability to create specific solutions to customer unique requirements. NMTG provides practical cost effective solutions with a commitment to value through quality.

4) What materials are NMTG Locking Assemblies made of?

Standard NMTG Locking Assemblies are constructed of low-carbon steel, Alloy Steel and high-grade fasteners.

For special Applications they can be manufactured from other materials such as stainless steel or alloy to offer a corrosion-resistant product or increase load rating for unique applications.

5) What range of sizes are available?

The size options range from (6 mm to 1000 mm) bores for shaft diameter Connection.

6) What are some advantages of NMTG Locking Assemblies versus others?

The NMTG product offering is the most comprehensive in the market and is available in 30 internal locking device designs and 13 shrink disc designs.

7) What is the typical torque capacity?

8 to 11872 kNm

8) What is the temperature range in which NMTG Locking Assemblies can be used?

-20 to 150 C.

Special designs available for different temperature needs.

9) Are shrink discs and NMTG Locking Assemblies the same thing?

Yes and no. ‘Shrink discs’ are the technical term for a type of locking device. A shrink disc is a style that clamps the equipment by using compressive forces over diameter of the equipment to the shaft. (External Clamping). This offering also includes internal locking devices that are different than shrink discs

10) How many configurations of NMTG Locking Assemblies are available and why?

There are 30 (approx.) standard styles available, each with unique features and advantages for specific applications.

11) Can I use the Locking assemblies if it is a little longer than the length of the shaft?

If the shaft length is shorter than the width of the Locking assemblies, the force to the inner ring becomes unequal, and it is impossible to use the Locking assemblies due to the resulting deformation. Because of deformation, the accuracy of the centering will also decrease.

12) I’m thinking of using a Locking assemblies with a hollow shaft. Will this cause any problems?

For a hollow shaft it is necessary to confirm whether the shaft material and hollow shaft diameter has the strength to withstand the pressure from the shaft due to the locking of the Locking assemblies. The calculation formulas and related details are listed in our catalogue. Please visit our online calculation program.

13) If I use a Locking assemblies series with no centering function and a hub with no guide portion, how does this affect centering accuracy?

It cannot be used because extremely large run-out will certainly occur, and its amount cannot be predicted. Make sure to always have the guide portion for centering the hub. If the length of the guide portion for centering is at least half that of the shaft diameter (d/2), you can obtain practical centering accuracy. In addition, decide the tolerance of the guide portion according to necessary precision.

14) What would happen if I didn’t use a torque wrench to install a Locking assembly?

The transmissible torque and thrust capacity described in the catalogue are the value when the locking bolts are tightened correctly. If the torque wrench is not used, the prescribed axial force will not be achieved, causing the Locking assembly to slip, and damaging the bolts or deforming the Locking assembly due to excessive tightening of the locking bolts. Make sure to use a torque wrench and tighten it according to the stipulated torque amount.

15) What happens when the Locking assembly is assembled without using a torque wrench?

The transmission torque and thrust load in the catalogue are the values when the Locking assembly 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 Locking assembly, the bolt may be damaged, or the Locking assembly body may deform due to excessive tightening. Be sure to use a torque wrench and assemble the lock with the specified tightening torque.

16) What would happen if I tighten the bolt at a torque level less than the prescribed amount?

The tightening torque and the Locking assembly transmissible torque have a proportional relationship. Therefore, if bolt tightening torque is reduced, transmissible torque will also be reduced accordingly, but we cannot recommend this because reducing tightening torque will cause the locking bolt to loosen.

17) When installing the Keyless Transmission Elements (Locking assembly & Shrink Disc), which portion do I have to apply oil/grease to?

It is necessary to apply light coat oil to the shaft and hub contact surfaces, as well as the mutual contact areas of the taper ring, inner and outer rings, and the bolt’s bearing surface and the bolt screw surface. It is sometimes misunderstood that when applying oil to the taper’s surface it can cause slip, but the lubricating effect is essential for smooth movement on the taper’s surface during assembly. However, do not use oil or grease that includes molybdenum with anti-friction composites. Also, do not use any oil or grease that contains extreme pressure additives. If oil/grease containing these additives are used, the friction coefficient will significantly decrease, possibly damaging the tightening bolt.

18) 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.

19) Can I reuse a slipped Keyless Transmission Elements (Locking assembly & Shrink Disc)?

Once the Keyless Transmission Elements has been completely disassembled, and no deformations or scratches have been discovered on any of its parts, by following the procedures for reassembly in the manual, it is possible to reuse it.

20) Will there be a problem if I use the Locking assemblies with oil bath lubrication?

This should not pose a problem if oil is added after tightening the Locking assembly. 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.

21) Can we use washers for the tightening bolts to prevent loosening?

No, you can't. When the Locking assembly 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.

Freewheel One Way Clutches

1) Does "backlash" occur in Freewheel clutch?

Freewheel clutch engages immediately without backlash when torque is applied in the engaging direction.

2) What happens when a thrust load is applied to Freewheel clutch?

Bearings that maintain concentricity of inner and outer races will wear out and generate heat, shortening their service life. There are also series without bearings, which can lead to internal damage. Therefore, if a thrust load is applied to Freewheel clutch, please prepare something that can receive the thrust load separately.