Handspinning
Handspinners use the number of twists per inch often. Because the amount of twist defines a lot about a yarn, the number of twists per inch is an important measure to recreate a yarn. As a spinner spins, they will often stop every few minutes to check to see that the number of twists per inch are the same throughout the yarn, as well as that the number of wraps per inch (the thickness of the yarn) are the same. Measuring the number of twists per inch while spinning singles also helps the spinner create a balanced yarn plying. Yarns that have relatively fewer twists per inch tend to have a softer hand but are not as strong as yarns with more twists per inch, such as medium twist or hard twist yarns. Yarns that have a very hard twist, enough so that the yarn will double back onto itself when released from tension are called crepe-twist yarns.
Read more about this topic: Twist Per Inch