My honey needs his Carhardts. They are made tough, but zippers seem to give out long before the things need patches. I've replaced the zipper on his overalls and today it was the zipper on his old coat. That thing had four rows of stitching on each side of the zipper! Taking it out was a major production, putting it back in wasn't as hard. I have to sing the praises of my old Husqvarna Constitution 200. It went through three layers of duck cloth and the zipper.
See the stained old coat? You can't really make out the new zipper. Honey was very happy.
If you're thinking about buying a sewing machine, I'm a big advocate for the Husqvarna.
God bless your evening.