Witness Machinists Repair a Damaged Engine Block Without Using Any Welds

      Syracuse Crank & Machine, LLC

      As a somewhat jaded, middle-aged individual from the East Coast, I rarely encounter something on social media that I've not seen before. I can still recreate the sound of an AOL dial-up connection from memory, okay? I've been online for quite some time. So, when Caleb shared a reel with me depicting Syracuse Crank & Machine repairing an old damaged industrial engine block using stitching (yes, stitching), I found myself genuinely intrigued. This led me down a brief Internet rabbit hole, so let me introduce you to a metal casting repair method known as Precision Metal Stitching, or Lock-N-Stitch.

      This is a proprietary technique intended as a replacement for scenarios where welding is impractical or has already failed. Instead of fixing a crack or break through heat or friction, this method introduces new metal in the form of pins. These pins resemble small bolts with wider heads, designed to pull the two sides of a cracked casting together. After installation, the large heads can be ground down for a smooth finish.

      To insert the threaded pins into the block, the machinist first needs to drill holes along the crack in a criss-cross pattern to ensure the pins can effectively close the metal gap through torque. Following this, the holes are tapped to accept the threaded pins, and a thread sealant is applied. Once the pins are securely fitted and tightened, the resulting repair should be strong enough to withstand compression in an engine block, for instance. While I hesitate to say it’s “good as new,” the outcomes certainly speak volumes.

      “The repaired, metal-stitched area is gas- and liquid-tight, providing a pressure-tight repair,” states the company’s website. “Moreover, metal stitching mitigates and absorbs compression stresses. It also redistributes tensile strains and spreads the load away from the original failure point, all while preserving the alignment of the original surfaces.”

      As seen above, once the pins have been ground down, the outcome closely resembles a weld—and is surprisingly tidy for a process that appears so… primitive. The company notes this technique is primarily used on cast iron but can also be applied to ductile iron, steel, aluminum, and bronze castings. Pretty fascinating, right?

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