Metal stitching, sometimes also called cold pinning, has been around for over 100 years. It is a very well established and proven technology. It is mostly used on cast (gray) iron components such as engine blocks and casings although the repair of other materials such as aluminium and bronze is possible too.
The advantages of metal stitching are many:
- Usually, little or no dismantling is necessary. Proper access from one side is generally sufficient.
- Since it is a cold-repair method, no additional stresses, which over time may lead to new cracks, are introduced into the material.
- The original alignments of the parts can be retained. There is no deformation or blemish due to the application of heat. Re-machining after repair is therefore often not necessary.
- The repair seam helps to distribute tensile stresses over a larger area
- If done properly, then the repaired area is liquid and gas tight. QuantiServ has successfully applied water pressure up to 12 bars (174 psi) to a test piece that was repaired by metal stitching.
After determining the extent of cracking, lines of holes are drilled at right angles to the crack. The holes are then converted to slots by connecting the holes. Preformed locks are inserted in the slots forming a connection across the crack. Then holes are drilled along the crack line between each stitch. These holes are tapped for placing special screws to fill the crack. The stitched area is ground to conform to the base metal contour, thus completing the repair.
If the component undergoing repair is not only cracked but if a piece is missing, then we prefabricate a new piece and lock it in place in the same manner as described above.
Over the years QuantiServ’s metal stitching experts have repaired many engine blocks, casings and other castings. We helped their owners and operators to save a lot of money and reduce the equipment down-time from the several months that it typically takes to produce, ship and install a new part to days or weeks at most. And since most of the metal stitching repairs on board ships were carried out during the voyage, any off-hire or other interference with the vessel schedule could usually be avoided.
Our metal stitching specialists recently repaired an extensive damage on a 12-cylinder, 40-bore engine block on a cruise ship. All work was carried out while the ship remained in service:
The following photos show the repair of a marine gearbox cover by metal stitching, carried out last year in Namibia:
Here is an example of a repair of a marine gearbox foot, carried out by QuantiServ’s experts in Russia recently: