Middletown, Ohio, USA, had been asked to find a way to roll 3.5% silicon grain-oriented steel down to 0.05 mm for the production of small transformers that would make airborne radar possible. ARMCO’s engineers tried a number of different approaches, all to no avail. Even the use of a narrow four-high mill with very small diameter sapphire rolls failed because the high lateral force caused the rolls to snap in the middle.