Barger 
Simple Machines Screw [PDF ebook] 

In Simple Machines: Screw, young learners in grades 1-3 will explore what a screw is and how it is useful. This 24-page title uses real-world examples of simple machine mechanisms and explains how these feats of engineering can make daily work less difficult to complete. The Simple Machines series for grades 1-3 explains how basic mechanical devices, that are used for applying a force, can help make daily tasks much easier. Featuring before- and after-reading activities, a glossary, an index, and comprehension questions, this series helps young learners strengthen their reading comprehension skills while also introducing them to some of the most commonly used simple machines