Metal Stitching

Metalocking and Metal Stitching

Metal stitching or metalocking is a method of repairing cracks in cast metals without the need of welding.

Cold repairs on all cracked or broken components made from cast iron cast steel or aluminium. Breakages usually occur because of overloading, accidents, equipment misuse or flaws in the casting.

The illustration of the Metalock repair system (Metalocking), shown below, is a basic repair to a flat surface. Damage to more complex fractures and castings requires the Metalock Engineer to draw on his skills and knowledge in coping with both the difficulties of the component’s shape, its operation and its environment. This all has to be completed, often with a minimum downtime, frequently involving 24 / 7 working.

Lloyds Register Certificate

Metalock Engineering UK have for many years held the Lloyds Register Certificate (No MNDE/REP/0017/06) for the repair of specified components by metal stitching using the "Metalock" and "Masterlock" processes.

Metal Stitching Repair Process

Metal Stitching Repair Process

  1. The fracture, after a survey and report has been presented to the customer, is positioned, realigned, and firmly held together by special fixtures and clamps.
  2. By the use of special Jigs, groups of holes are drilled across the line of fracture to the tool depth of the casting.
  3. The Metalock Key is a multi-dumbell shaped section of highly ductile alloy, the size and length being selected to suit the type of fracture.
  4. The holes are then joined by the use of pneumatic chisels to conform to the shape of the Metalock Keys.
  5. Individual layers of Keys are inserted in the apertures and peened into a metal-to-metal condition, which becomes almost integral with the parent metal.
  6. Holes are then drilled along the line of the fracture, then tapped,
  7. and filled with studs,
  8. each stud biting into it’s predecessor, resulting in a pressure-tight join and restoring a rigidity to the casting.
  9. A Metalock stud is an important aspect of the Metalock process, bearing in mind that pressure repairs are often required.
  10. The studs are then run down till the heads shear, the remaining rough metal being removed by pneumatic chisels.
  11. The whole repair receives treatment from hand grinders
  12. prior to it’s final coat of paint

The Casting Repair Process

The Metalock process is based on sound engineering principles which have been accepted for more than a century.

The casting repair process
  1. Holes drilled along the line of fracture, tapped and filled with studs.
  2. Holes drilled at right angles to the fracture.
  3. Holes drilled to form shape of Metalock keys.
  4. Layers of keys peened into metal-to-metal condition.

Metalock Casting Repair Diagram

Metalock casting repair diagram
  1. Using a drill jig, rows of blind holes are drilled perpendicular to the direction of the crack, each row to act as a key.
  2. The intermediate partitions are removed with pneumatic chisel.
  3. Metalock keys are driven into the opening and caulked.
  4. Holes for Metalock screws are drilled along the crack between the keys.
  5. The screws are fitted to ensure they overlap, effecting a seal along the fracture.
  6. Finally, the entire installation is caulked to ensure stability and pressure tightness.

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A trusted technique used to repair machines and structures

Whilst the tried, tested and unique repair system is a repetitive operation, the application is as varied as the plant and machinery for which it is designed. This extends from ship’s engines to power presses and petro chem refineries to heritage buildings.

Over the 75 years since the inception of the process, Metalock Engineering has developed special tools, jigs, fixtures and materials to facilitate the repair which enables the restoration of machines and structures to their owner’s satisfaction.

Cracked Marine Gearbox

Images above from top left: Cracked Marine Gearbox. Another Section that's broken off. Gearbox being machined for new insert. Machining complete. Repair complete and gearbox painted red

Some of the advantages of Metalock process:

  • Dampens and absorbs compression stresses
  • Provides a good ‘expansion joint’ for such castings as cylinder liners, diesel heads or any vessels subject to thermal stresses
  • Distributes the tension load away from fatigue points
  • Maintains relieved conditions of inherent internal stresses where rupture occurred
  • Maintains alignment and original surfaces, since lack of heat produces no distortion
  • The vast majority of repairs can be done in situ, with consequent savings in time with little or no dismantling.

Metalock UK has an excellent record with performing cast iron repairs using the cast iron stitching method. Using the metal stitching technique to fix metal cracks is the preferred solution as it is always a challenge to weld cast metals.

Benefits of Metalock metal stitching include:

  • On-site insitu metal stitching repair 24 x 7
  • Less downtime - production is up and running again
  • The procedure and process is recognized throughout the world
  • The cold repair process is far more cost effective than the purchase of new, expensive cast parts
How can we save you time and money, and help you protect your reputation with our casting repair techniques?

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