One other thing about spinner knobs. They are heavy. Where ever they stop the knob will always stop DOWN. You might want to decide if you want the needle down or up when you have the knob down. Then attach it the way you want the needle to end when you stop. If you are teaching them to turn a lot of corners you might want the needle down. If you are teaching them to stop with the needle up you might want to set the knob so the needle is up when the knob is down. Some machines won't work like that - the Franklin Rotary had a pin to release the clutch that got in the way. If they are just sewing holes in bags it won't matter.