Answer MEP Question 36
Q. What is Metal-locking? What types of repairs are carried out by metal-locking? Describe the repair procedure using Metal-Locking.
A. Metal Locking or metal stitching is a precise mechanical method of making permanent repairs to broken casting and mechanical parts.
There is no heat involved in the method, thus post-repair there is no need to correct any misalignment and warpage, also the repair can be carried out in the restricted area where it is hazardous to carry out hot work. This method of repair does not require any major disassembly.
a. A Jig to drill the holes across the fracture equidistantly,
b. Dumbbell-shaped Nickel alloy metal-lock keys. Which is a ductile alloy. They are available in different sizes.
c. Studs whose heads can be sheared off.
d. A Mechanized chisel to join the drill holes, size is such that to match the contour of the key.
e. Drill machine and drill bits of required size to match the keys and studs.
f. Hammer to tap the keys.
g. A chisel for the removal of remnant rough metal.
h. Grinder to ground the burrs.
a. With the help of a Jig & Drill machine, series of holes are drilled across the line of fracture, to the depth of the workpiece.
d. Holes are then drilled along the line of the fracture, then screwed in with the studs.
f. The remnant rough metal is removed by chisel. Protruding burrs are grounded by a grinder and a coat of paint is applied as required.
There is no heat involved in the method, thus post-repair there is no need to correct any misalignment and warpage, also the repair can be carried out in the restricted area where it is hazardous to carry out hot work. This method of repair does not require any major disassembly.
a. A Jig to drill the holes across the fracture equidistantly,
b. Dumbbell-shaped Nickel alloy metal-lock keys. Which is a ductile alloy. They are available in different sizes.
c. Studs whose heads can be sheared off.
d. A Mechanized chisel to join the drill holes, size is such that to match the contour of the key.
e. Drill machine and drill bits of required size to match the keys and studs.
f. Hammer to tap the keys.
g. A chisel for the removal of remnant rough metal.
h. Grinder to ground the burrs.
B. Cast Iron components when cracked are not advised to repair by welding whereas metal locking is a suitable method to carry out such repair. Also, steel, bronze, or aluminum structures or components are also repaired by metal locking.
C. Procedure:- A skilled technician or engineer is required to carry out this repair. Shore-based workshops approved by classification societies are generally available for such repairs.
Following are the steps to carry out metal locking:-a. With the help of a Jig & Drill machine, series of holes are drilled across the line of fracture, to the depth of the workpiece.
b. Drill holes are then joined in common by using a mechanized chisel.
c. Keys are then driven into the aperture and peened into a metal-to-metal condition, causing the key to virtually become integral with the parent metal.
e. Stud as screwed in should bite into the predecessor, forming a pressure-tight joint. This makes the casting a more rigid body. The heads of the studs are sheared off.
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