My Mom got her 15 in 1936 while my Dad and his brother, who lived with them, worked in the mines. Mom mended the men's work overalls as well as making baby clothes on her 15. During the war they when we had rationing in this country, they went to Mexico and bought denim by the bolt. She made everything from jeans to jackets, even wool lined coats, on that machine. The 15 will easily sew through 4 layers of denim for jean seams. It's just as strong today as it was in 1936.