Principles of Torque Management

As Mr. Bickford states so clearly, obtaining the proper clamping force is absolutely critical to the performance of a joint. In servicing vehicles this has several ramifications, including but not limited to:

• Using the correct fastener for the joint as specified by the vehicle system manufacturer or vehicle OEM.
• Insuring the condition of the fastener is appropriate to the task.
• Installing the fastener correctly.
• Assuring the fastener is properly torqued.

The first three bullet points are covered by the vehicle system and OEM specifications and by industry consensus standards. These are the appropriate sources of information about those topics.

The fourth point, the torque, is what we will address here.

Torque control is a process, not an event. The tool that is in the technicians hands when the torque is applied to the fastener is the last link in a chain of processes that is international in its' reach. Making sure the chain is intact is what torque management consists of.

Torque is a twisting force, a force that tends to twist a body about an axis of rotation. This force is always stated using a unit of measure that has two components, a force and a distance. The torque is the force times the distance, and the units of measure reflect this.

Pound-Feet or Foot Pounds: a foot is a measure of distance and a pound is a measure of force.

Newton meters: a meter is a measure of distance and a Newton is a measure of force.

Kilogram•meters: a meter is a measure of distance and a kilogram is a measure of force.

The definitions of the basic units of force and distance (and other technical units) are essential to all technical processes and all commerce. Imagine what would happen if a "foot" or a "pound" was a different amount of distance or force in each country. Utter chaos.

For this reason governments have established national and/or regional standards laboratories that work together to define the necessary units of measure in a manner that is consistent on a global basis. As a result, a millimeter or a foot or a kilogram or a pound has the exact same definition around the globe. National and international commerce can proceed in a productive manner, resting on this base of constants.

In the United States, the national standards for these constants are defined and maintained by the National Institute for Standards and Technology (NIST) (http://www.nist.gov/). NIST evolved from and replaced the National Bureau of Standards, and is the entity to which we turn to assure technical accuracy in this country.

There are other standards that are used every day and are applicable to the chain that leads to the technician and the tool in his or her hands. These are organizations of firms and individuals that work to establish standards for objects and materials not covered by NIST. These organizations are called "consensus standards organizations" and they write standards that commercial firms agree to. Once again the goal is technical accuracy and consistency.

Consensus standards organizations include several that also are directly applicable to the task of torque management, such as:

SAE – the Society of Automotive and Aerospace Engineers

ASTM – the American Society for Testing and Materials

ASME – the American Society of Mechanical Engineers

These organizations provide us with specification stability in areas that directly affect the performance of the components of the joint such as the steel, the threads, and the strength of the bolt or stud and the nut. These are standards the product design engineers rely upon when designing the system and/or vehicle on which we will use the torque tools and apply our skills.

The OEM or system engineers create specifications for the maintenance of the system or vehicle. These specifications are what we rely upon to provide the "how much" and "when" for torque application.

Industry consensus organizations create sets of standard practices that the industry members can use to guide them in the vehicle diagnostic and repair processes, inclusive of reassembly. These industry consensus organizations are often made up of industry firms, individuals from the industry, and system or vehicle technical people. Examples of these organizations include:

TMC – Technology and Maintenance Council (Part of the American Trucking Association)

TIA – Tire Industry Association

All of these elements – governmental entities, system and vehicle OEM's, and industry associations provide components used in the management of the reassembly process including the torque management process. These elements are related to each other in the manner depicted in the graphic to the left. [Click small graphic to enlarge.]

These elements may be viewed as building blocks for the torque management process. A moment's thought will show that each rests on the other and that they are designed to enable the management of a firm to apply them in confidence.

Sound quality management rests also upon several principles. These principles are straightforward, and are embodied in the ISO 9000 standard for quality. They are:

• There must be a policy that states the company's position in the specific area addressed.
• There must be properly written procedures and instructions for carrying out the work in accordance with the policy.
• There must be appropriate training for the people who will be performing the work.
• There must be appropriate tools and equipment for them to perform the work with, and the equipment and tools must be properly calibrated and maintained.
• All of the above must be checked (inspected or audited) periodically to make sure they are properly performed and executed.
• All of the above must be documented.

At first it appears this is simple common sense, and to a large extent it is. The challenge lies in creating systems that address all of the required elements in an effective manner, and combining that with the technical expertise and hardware to insure its effectiveness.

The rewards for meeting the challenge are many. Actual costs go down since the cost of errors in the system and in the customers’ experience with your service decline, resulting in hard-dollar savings on an ongoing basis. The firm with superior quality can get a premium for that quality; few people drive a Yugo, even though it is the cheapest car in price. Processes with fewer errors means there is less likelihood of an error causing harm to others, which has several positive effects. First, it means that there will be fewer claims made to recoup costs from you, be they repairs or something more expensive. Second, over time this statistically-verifiable history has a positive effect on the reserves set aside for such occurrences and on that can affect insurance premiums for those not self-insured. There is also the benefit to reputation that accrues to those whose services are of superior quality and who market the difference actively. This eases the sales process for those in vehicle service and in fleet management.

Mr. Crosby (one of the genuine leaders in quality improvement in the United States) proclaimed a couple of decades ago that “Quality is free”. Experience has shown that he was overly modest. Superior quality is highly profitable.

Tenexes Div. of Ryeson Corporation
3203 N. Wolf Road • Franklin Park, IL 60131
Phone: 847/260-2050 or 563/249-4170 • Fax: 847/455-0347

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