What is the strongest way to attach two steel parts together? In this video, we test shrink fitting – a method where steel is heated so it expands, assembled while hot, and then locked together as it cools down. Many people don’t realize that heat alone can create an extremely strong mechanical joint, without bolts, welding, or glue. We compare three different methods: Glue (thread locker) A reasonable shrink fit An unreasonable shrink fit After assembling the parts, we use the hydraulic press to push them apart and measure how much force each method can handle. Some joints come apart surprisingly easily — and one of them gets seriously stuck. This experiment shows: how powerful shrink fitting really is why surface finish and tolerances matter and what happens when a fit becomes too tight If you’ve ever wondered how industrial steel parts are joined — or what happens when you push those limits — this one is for you.