1 Discard any hammer with mushroomed or chipped face or with cracks in the claw or eye sections. 2  Wear safety glasses or goggles, or a face shield (with safety glasses or goggles).  Strike a hammer blow squarely with the striking face parallel to the surface being struck.
The first jet airplane was the Heinkel He 178 made in Germany in 1939, right before the outbreak of World War II .
1916 - The first tank prototype, nicknamed mother, was created by Britain during World War 1. 1926 â Robert Goddard launches the first liquid-fueled rocket. 1935 â First flight of the DC-3, one of the most significant transport aircraft in the history of aviation; 1939 - First jet engine powered aircraft, the Heinkel He 178, takes flight.