Technically the Metalock method is simple. A crack in a cast iron component is locked using a key which takes up both tensile and compressive stresses. Screws are “driven” in along the crack in order to take up shear stresses.
During the repair the metal actually "flows" with the hammers to fill the whole of the aperture which compensates for the slight imperfections due to drilling. The keys are very accurately formed to ensure a very good fit in the apertures.
It is possible to determine the tensile strength lost when a casting is fractured and we are able to accurately calculate the amount of strength restored by the Metalock keys.
The apertures for the keys are prepared at set centres and at right angles to and across the line of the fracture to the exact female form of the Metalock keys. The accuracy of this work relies mainly on the experience and craftsmanship of the Metalock engineer although he does make use of jigs and fixtures.
Material Used In Metalock Process
The material used in the Metalock process is a Nickel Alloy. The advantages this material has is its ductility in the annealed condition, giving reasonable tensile strength when work hardened, a low rate of strain hardening and a very low coefficient of thermal expansion, similar to cast iron. Corrosion resistance is greater than steel or cast iron and these qualities make it an ideal material for most repairs.
Variations of the Metalock Process
Masterlocks are often used in conjunction with the Metalock process, in points of high stress concentration or in sections subject to overloading and subsequent fracture. They are comprised of inlays of high strength alloy plate held in place by dowels, cold worked into matching half holes between the parent material and the alloy plate. The Masterlocks vary in size, shape and even material, dependant upon requirements of each repair.
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