The main limitation of a sewing machine is the height that the presser foot will rise, and how strong the motor is.
Most sewing machines aren't designed to sew anything beyond heavy fabrics. You really have to go industrial to get a strong enough machine to take the punishment of jamming a needle into leather, and to handle a thick enough thread.
I'm getting my info through osmosis because the wife is a seamstress and has several machines of differing capabilities. We recently got an old Singer 202 (I think, not my department

) and its foot doesnt rise more than 1/4", not enough to do a sheath, but enough to do heavy canvass and light upholstery leathers. Her industrial walking foot machine is good for light leather, but again, its presser foot doesn't rise far enough for a sheath, but belts are a breeze. Our Tippman BOSS is the only one that I can comfortably say is heavy enough to do anything up to 3/4", NO thicker.
Manual Machine: Tippman BOSS
Electric: Cobra and Artisan
All three are considered heavy duty stitchers not sewing machines. They're made for stitching heavy leathers and do it very well. Cost is a huge factor though.