Machines with a metal frame tend to be more durable and heavy-duty, which makes them more suitable for these heavy fabrics. That doesn’t mean a model with a plastic frame won’t be able to sew them, but it might not sew them as quickly. No matter what type of machine you have, it helps to use the right kind of thread and needle for heavy fabrics. Denim needles are larger and thicker, and denim thread is heavier and thicker than average thread.