are you using the same thread, top and bottom? Also your needle needs to fit your thread (check out Superior Threads for explanation) Change your needle (I use 90/14), then sew a straight line.....if the tension is OK, don't mess with the settings. If the thread is rough the larger eye of a topstitch 90/14 might handle it. Otherwise, I would order the closest match from Superior and have a chat with your friend.