How many do I need? None. I started with the quest for a key. I had not opened the ancient machine in decades. What was the rush? None. Then in one day I acquired two more sewing machines. These were well built…and heavy! Another? Nope! But low and behold…in an antique shop… a machine was waiting. It’s different yet again…and much the same. And the price …$22. Whoa! A real bargain! Darn! That machine pretty much climbed into the back of the car all by itself.