I'm sure many of us have had wheel bearings go out and had the inner part of the bearing weld or seize itself onto a spindle... or had other circumstances where two pieces of metal have become fused together by heat expansion making them near impossible to separate. Then there are man-made welds (done by a welder of any sort) in which we intentionally join metal together and want it to hold. Now, take my car trailer. Any man made weld with a welder, no matter how good the person is at welding, will break and not hold. After not checking wheel bearings for 9 years on my trailer and having them in perfect shape last June, and re-packing them properly with new grease last June, one of them decided since it was finally properly maintenanced that it would fry itself 7 months after having new grease. Now, the inner part of the bearing has fused itself to the spindle by such strength that far surpasses any other weld on my trailer. In order to break it away from the spindle seems to require such force as no man made weld would ever handle. Why is this. End of my complaint against the laws of physics for today.