Since I am a retired Home Economics teacher I am in favor of using my machines to help others learn to sew. I have several machines, vintage and new. I use them all. I see no problems with sewing denim squares. Just be sure to use the proper needle and thread. I would certainly be on hand to teach someone before turning them loose on their own. I love to sew and quilt and I want others to love it also-so I have a measure of responsibility. I would not use machines that I knew to have problems-that is discouraging.