5 Things to Know Before Buying Spring Flat Steel

19 May.,2025

 

Flat Springs: The Hidden Force in Your Everyday Life

Who says flat steel springs are dated? Genius artist and inventor Leonardo da Vinci (–) used flat steel resources in many of his creations, many of which were ahead of their time. Flat steel springs were a part of many of his inventions, including the self-propelled cart and the first iteration of a helicopter, and yet, today, flat springs are part of our lives.

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Flat steel springs may often be overlooked by their round wire counterparts, but we will explore more about them to give them the recognition they deserve.

Types of Flat Springs

There are several types of flat springs, from cantilever, leaf, and flat coil to volute and Belleville, but we will focus on constant force springs, which are used where a consistent force is needed over a range of movement.

Why Use a Constant Force Spring?

Constant force springs, like our Conforce Spring, offer high-force output with small space requirements. They also provide long linear reach with minimal force buildup and store energy indefinitely when extended, making them ideal where constant force is needed.

They are applied in many industries and fields, such as aerospace & defense, medical devices & healthcare, and more. Some common applications include:

  • Counterbalancing: Ideal for windows, shades, hospital tables, X-ray machines, industrial equipment, and military tank seats.
  • Push or Pull Mechanisms: Integral to staple and nail guns, surgical staplers, drug delivery devices, motor brushes, toasters, cupholders, fire dampers, retail displays, and more.

Constant force springs are also used in smart device mechanisms, wearable technology, and furniture and ergonomic products to facilitate smooth and effortless adjustments.

Key Design and Ordering Considerations

If you are considering a constant force spring, several factors are crucial for optimal performance:

  1. Material Selection: The most common material is type 301 stainless steel. Texture-rolled high-carbon steel can be used when a lower cost is required for high volumes; Inconel 625 and Elgooly are utilized for the most demanding applications. Material thickness generally runs from .002” to .031”, and tensile strength ranges from 270,000 to 310,000 psi.
  2. Cost: 301 Stainless is the most commonly specified material. Inconel and Elgioloy are significantly more expensive than texture-rolled high-carbon.
  3. Volume Timing Needs: Estimate the number required and production timeline. Define critical characteristics, tolerances, and packaging needs.
  4. Force & Diameter Relationship: As the spring diameter increases, the spring force decreases, and cycle life increases due to lower stress.
  5. Testing and Inspection: Design aspects like coil diameter, end detail, length, load or force, drum size and mounting, and workmanship are typically tested, inspected, and matched to the customer’s requirements.

Constant Force vs. Constant Torque: What’s the Difference?

Constant Force Springs provide a linear extending/retracting force. In contrast, Constant Torque Springs, like our Contorque Spring, offer high amounts of torque with small space requirements and can be designed to produce a constant torque or a positive or negative gradient output.

Conclusion

Whether we see them or not, flat springs are in our day-to-day lives, enhancing functionality, safety, and convenience in numerous everyday applications. If you need to work with these, always choose high-quality, well-designed products. Choosing the right supply partner, such as Vulcan Spring, can help you achieve effortless results. At Vulcan Spring, we go “Beyond the Spring” to support your engineering innovations with expertise and dedication.

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AISI

Stands for American Iron and Steel Institute. The institute serves as the voice of the North American steel industry. AISI numbers are used to categorize metals by alloy type and carbon content, and they do it with four digits. The first two digits of an AISI number refer to the alloy type, and the second two digits refer to carbon content.

ALLOY

A metal made by combining two or more metallic elements. An alloy typically possesses qualities different from those of the components used to create it.

ASM

Stands for American Society for Metals. ASM International is the world’s largest association of metal material engineers and scientists. The association engages and connects materials professionals and their organizations to the resources necessary to solve problems, improve outcomes, and advance society.

ASTM

Stands for American Society for Testing and Materials. ASTM International is a not-for-profit organization that develops standards for materials, products, systems, and services. Metal with an ASTM designation meets the international standards for quality and regulations.

CUT-TO-LENGTH

This process levels coil into a flat sheet or blank. The service provides better length and width tolerances than sheared product, and it can improve diagonal tolerances as well.

DEBURRING

Cutting metals can leave behind burrs, which are unwanted raised edges or protrusions. Deburring is the process of removing these burrs with a tool.

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DRAWING

Drawing is a metalworking process that uses tensile forces to stretch metal. As the metal is drawn, it stretches thinner, into a desired shape and thickness.

DRAWING TEMPERATURE

Drawing is usually done at room temperature, classifying it as a cold working process. However, it may be performed at elevated temperatures during special applications like on large wires, rods, or hollow sections in order to reduce forces.

ELONGATION

A metal fabricating term that refers to the degree to which a material can be bent, stretched, or compressed before rupturing. A metal’s elongation is a point between tensile strength and yield strength, and it is typically expressed as a percentage of the original length.

GAUGE

The thickness of sheet metal in the USA is commonly specified by a traditional, non-linear measure known as its gauge. The larger the gauge number, the thinner the metal.

HEAT LOTS OR HEAT NUMBER

A heat number is an identification number that is stamped on a material plate to prove it meets industry quality standards which require materials to be tested by the manufacturer. The heat lot or heat number is used to identify production runs for quality control purposes.

EDGE ROLLING

Edge rolling is the process of adding finishing edges to metal. It forms the edge of a strip to the desired shape beyond that of a standard slit edge.

MIL STD

Stands for Military Standard. This classification establishes uniform engineering and technical requirements for military-unique or substantially modified commercial processes, procedures, practices, and methods. In order to qualify, materials have undergone rugged, exact testing, equal to the exigencies of combat use.

NORMALIZING TEMPERATURE

Normalization is a heat treatment that relieves stress on steel to improve ductility and toughness in steel that may harden after the cold working process. During normalization, steel is warmed to a temperature just above its upper critical point. Normalized heat treatment facilitates a more uniform final product.

ROCKWELL SCALE

The Rockwell Scale indicates the hardness of materials. Rockwell hardness numbers are most often used to describe the hardness of metals, although they are also used for some plastics. The Rockwell scale is based on measuring the depth of the indentation made by pressing a diamond point into a material.

SAE

Stands for Society of Automotive Engineers. SAE International is a global association of engineers and related technical experts in the aerospace, automotive, and commercial-vehicle industries. Materials meeting SAE standards are internationally recognized for safety, quality, and effectiveness.

SLITTING

Slitting is a precise shearing process, but instead of making cuts at the end of a workpiece like shearing, slitting cuts a wide coil of metal into a number of narrower coils as the main coil is moved through the slitter. During the slitting process, the metal coil passes lengthwise through the slitter’s circular blades.

TEMPER

Temper refers to reheating hardened, normalized, or mechanically worked steel to a temperature below the critical range to soften it and improve impact strength. Tempering results in greater toughness by decreasing an alloy’s hardness.

TENSILE STRENGTH

The maximum stress a material will withstand before fracturing or breaking. The ultimate tensile strength is calculated from the maximum load applied during the test, divided by the original cross-sectional area.

UNS DESIGNATION/NUMBER

Stands for the Unified Numbering System for Metals and Alloys. UNS designation provides a means of correlating internationally used metal and alloy numbering systems currently administered by societies, trade associations, and those individual users and producers of metals and alloys. This system is meant to avoid the confusion caused by using more than one identification number for the same metal or alloy, and the opposite situation of having the same number assigned to two or more different metals or alloys.

YIELD STRENGTH

The amount of stress a material can withstand before causing permanent deformity.

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