Repair And Fix it

Crankshaft pulley bolts are among the toughest bolts to break loose on vehicles, simply because they are constantly rotating, subjected to high heat and require a high torque value to stay tight. In order to prevent the pulley from turning while loosening the bolt, youll need a crankshaft pulley holding tool. This tool bolts to the inside of the crankshaft pulley using the holes cast into the steel pulley spokes. You can rent or purchase this tool from most auto parts stores.

Instructions

1

Alight the holes in the crankshaft pulley holding tool with the screw holes on the inside of the crank pulley.

2

Install the bolts that came with the crankshaft pulley holding tool with a ratchet and metric socket. Snug the bolts tight so the tool is firmly secured to the pulley.

3

Place a metric deep-well socket on a T-handle breaker bar, then slide a small diameter steel pipe over the breaker bar; the pipe will give you the increased leverage you need to break the crank pulley bolt loose.

4

Grab the crankshaft pulley holding tool in one hand, then grab the breaker bar and pipe in the other. Hold the pulley still with one hand while you break the bolt loose with the other. If the bolt is extremely tight, you may need an assistant to hold the pulley still while you focus on breaking the bolt loose.

Carriage bolt assemblies are threaded fasteners with a bolt that has a rounded, dome-shaped head. The bolt has a square neck that extends from the head towards the threads. A regular hex nut or wing nut allows the assembly to hold the components together. This assembly can be tightened with just one wrench.

Function

When used in metalworking applications, carriage bolts are often called plow bolts. These bolts must go through a square opening to accommodate the neck, which will keep the bolt from turning when the assemblys nut is tightened.

Considerations

Carriage bolt assemblies are commonly used in carpentry and construction; they are well-suited for fastening two structural wood pieces together, especially when extra strength is required. The square neck sinks into the wood as the fastener is tightened, preventing the bolt from turning and countersinking the bolt head at the same time.

Types

Carriage bolt assemblies are available in varying degrees of hardness, or grades. Grades three, five and eight are common strengths. Zinc is the most common coating for a carriage bolt. They are also available in silicon bronze.

Nuts and bolts are the glue that hold together our mechanical contraptions. These simple devices are one of the most important inventions of the mechanical age. The 12.9 bolt is a higher tensile bolt made from alloy steel that is quenched and tempered. They are commonly used at high stress points in connecting devices.

12.9 Bolts

A 12.9 bolt is one of the highest grade of bolts produced. Known for their high tensile strength, they are built with both hex and Torx heads and are available in zinc or chrome finishes. A 12.9 bolt is tightened with a torque wrench to 90 percent of its proof load. Because of their hardened surfaces, lock washers are ineffective because they cant bite into the metal.

MPa

The strength of a 12.9 bolt is rated in MPa, or megapascals. A Megapascal is equal to one million pascals. A pascal is a unit of pressure that is equal to one newton of force applied over an area of one square meter. A newton (N) is a measurement of force relative to gravity. One newton is equal to the force required to accelerate one kilogram, at a speed of one meter per second.

Shear Strength

The shear strength of a bolt is a measurement of the minimum amount of force needed to break the bolt into two pieces. The shear strength of a metal bolt is approximately 0.6 times its tensile strength. A bolt commonly shears where its head meets the threads.

12.9 Shear Strength

The minimum tensile strength of a 12.9 bolt is 1220 MPa. Therefore, the approximate shear strength of a 12.9 bolt is 732 MPa. The minimum yield strength of a bolt is the pressures needed to stretch the metal of the bolt. A 12.9 bolt has a minimum yield strength of 1100 MPa.