I have been experimenting with sewing leather. I didn't think that my machine could handle sewing leather, but with a Teflon foot, leather needles, sewing very slowly, and paying attention, I can sew lightweight leather on my current sewing machine. In fact, it is very like sewing heavy fabric like denim. However, if I have to sew through more than two layers, my poor machine will not do it. It doesn't seem to have the punching strength to go through that much tough leather.
So in July, I purchased a used industrial Pfaff sewing machine. The sewing machine mechanic said that it was previously used to sew leather on shoes at Nike. Anyway it is equipped with a roller foot, and he set it up so that it uses regular household current and has an adjustable speed knob. It certainly goes fast enough for me even on it's slowest speed. It is kind of scary how fast and powerful it is and I need much more practice on it before I can feel comfortable sewing on it. However, I haven't found any amount of leather that this machine cannot sew. (Well, it is limited by how much I can fit under the presser foot).
I have been practicing and making some things using both this new machine and the regular sewing machine. But I had to get a supply of industrial needles, different bobbins and some heavy duty nylon thread to work with the leather. I will be posting some of my efforts here in the next couple of days.