I have a child's sewing machine and it goes very slow, but is really easy to get straight lines. (Because it's really small and portable I confess to borrowing it myself.) I wish I had it when my girls were smaller. I agree- it's when they show interest and responsibility. The child must be able to follow your instructions, and as long as they can do that, then they can start very young. As with any subject with kids, some are gifted and way beyond their years, and others won't be ready for some time. Take it child by child. If the child has the interest, follows instructions really well, and you have the time to fully pay attention to the child, then enjoy your time together building memories!