Primary/Junior (Gr. 2-4) "The simplest of tools--levers, pulleys, wedges... are the subjects of the Science Matters: Simple Machines series... their principles are intelligently explained and bolstered by... vivid photos... De Medeiros' description of the object's function is unusually elegant... Subsequent pages describe how counting the threads on a screw can predict how many turns it will take to immerse it, point out where "worm gears" can be found in your home, compare... drill bits, and discuss the invention of the screw in ancient Persia. One gripe... admittedly "Phillips-head" is an informal term; leaving it out is probably a disservice to readers. However, the back matter (including online suggestions, a craft, a quiz, a well-chosen glossary... ) is strong and features... (a) 10-word index... " - Booklist, Oct 1/09.

Includes index.

What is a screw? -- Sharp threads -- Pushing ahead -- Screwy gears -- Gaining an advantage -- Nuts and bolts -- Drilling bits -- Early screws -- Screws on the Web -- Science in action -- What have you learned?.