A breaker bar (also known as a ''power bar'') is a long non-ratcheting bar that is used with

socket wrench A socket wrench (or socket spanner) is a type of spanner (or wrench in North American English) that uses a closed ''socket'' format, rather than a typical open wrench/spanner to turn a fastener, typically in the form of a nut or bolt. The most ...

-style sockets. They are used to break loose very tight fasteners because their additional length allows the same amount of

force In physics, a force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. In mechanics, force makes ideas like 'pushing' or 'pulling' mathematically precise. Because the Magnitu ...

to generate significantly more

torque In physics and mechanics, torque is the rotational analogue of linear force. It is also referred to as the moment of force (also abbreviated to moment). The symbol for torque is typically \boldsymbol\tau, the lowercase Greek letter ''tau''. Wh ...

than a standard length socket wrench.U.S. Patent 4,811,638 (1989)
Retrieved 3 May 2010 Their use prevents damage to the ratcheting mechanism of a socket wrench. Often, after the first half turn, the fastener is loose enough to be turned with a socket wrench.

Function

The long handle on breaker bars compared to shorter wrenches allows a larger torque to be generated with the same amount of force. It is effectively a

lever A lever is a simple machine consisting of a beam (structure), beam or rigid rod pivoted at a fixed hinge, or '':wikt:fulcrum, fulcrum''. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, l ...

, one of the

simple machines Simple Machines was an American independent record label in Arlington, Virginia. The label was founded by Derek Denckla and Jenny Toomey and Brad Sigal while both were living in the Positive Force House in north Arlington, but Sigal and even ...

. Also, the absence of a ratcheting mechanism makes a breaker bar considerably stronger than a ratchet. This allows greater torque to be applied to a fastener without the tool failing. A breaker bar can be improvised by inserting a wrench into a length of metal pipe to increase the available torque by using the pipe to extend the effective length of the breaker bar. A pipe used for this purpose is called a

cheater bar Cheating generally describes various actions designed to subvert or disobey rules in order to obtain unfair advantages without being noticed. This includes acts of bribery, cronyism and nepotism in any situation where individuals are given pr ...

or snipe.

Materials

A breaker bar is able to create a larger amount of rotational force compared to a standard socket wrench. A standard breaker bar is strong enough to allow the user to apply up to of torque without breaking the bar. A high-end 1/2" socket wrench can withstand a maximum of of torque. Since the breaker bar creates and withstands a larger amount of torque it is often used in place of a standard socket wrench to break loose tight-fitting fasteners. To be able to create these high torque numbers breaker bars have to be made out of a metal of adequate strength properties. High-quality breaker bars are typically made of chromium-vanadium steel (AISI 6150). Chromium-vanadium steel is known for its high strength, excellent toughness, and shock resistance. Chromium vanadium steel has a yield strength at 0.2% offset of 84.0 kilo-pound per square inch (KSI). Meaning, chromium-vanadium steel can withstand up to 84 KSI before it begins to yield. If the steel is unloaded before the yield point it is elastic and the material will return to its original configuration. Because of its high yield strength and shock resistance, standard socket wrenches, and breaker bars are fashioned from this material. In addition to its high yield strength, chromium-vanadium steel provides resistance to abrasion, oxidation, and corrosion making it a viable material for the production of tools.

Physics

Rotational force, also known as torque, varies depending on where the force is applied. If the force is applied closer to the object the torque is smaller than if the same amount of force is applied further from the object. A breaker bar creates a larger force due to the amount of torque that can be applied through a longer handle versus a shorter one. A lever arm, also known as a moment arm, is an important factor to consider when measuring the torque of a breaker bar. Having a longer lever arm creates a larger surface area for the force to be applied, which increases rotational force. Surface area is the measure of the total amount of area an object occupies. When the radius of the moment arm is increased, the surface area is proportionally increased. The concept that torque is related to a larger moment arm is shown in the torque equation. The torque equation can be written as follows: 𝜏 (Torque) = F (Force) x r (Radius). Since the force applied is multiplied by the radius of the moment arm, having a larger radius subsequently creates a larger torque. This makes the torque value on the point of rotation much greater as the size of the handle or moment arm increases.

References

{{Hand tools Wrenches