|MadSci Network: Engineering|
Historically lead shot has been produced in "shot towers." You can find a number of links on the internet to historic shot towers including the shot tower in DuBuque, Iowa, http://www2.iptv.org/interactive/miss/journal/trip8/dubuque.html Potosi, Missouri http://www.bchm.org/Photos/p365.html Baltimore, Maryland, http://www.baltimore.to/ShotTower/ and Tasmania http://www.talune.com.au/waterways/shottower.html Buck Conner provides a very interesting history into manufacturing bullets and shot at the following site: http://www.klesinger.com/jbp/lbus.html In the article, you also find a clue as to how shot is made today. Historically, molten lead was dropped through holes in a copper plate in order to form shot. As the lead shot dropped down the tower, surface tension caused the lead droplets to form into round balls. At the bottom of the tower, the partially solidified balls dropped into a water bath where they were cooled. The shot was then screened in order to separate the shot by size; shot that was out of round was then returned to the top of the shot tower to be remelted once again. The taller the shot tower, the larger shot that could be successfully produced, since the larger shot needed more time falling to cool. As implied in Mr. Conner's article, large shot towers can be replaced by providing a forced flow of cold air up a shorter tower, the speed of the air flow will help to determine how large shot can be successfully produced. Modern manufacturers try to protect their manufacturing secrets well. However at http://www.stepfour.com/jobs/titless.htm I found a listing for three jobs that help to understand how shot is being produced today; a shot dropper (http://www.stepfour.com/jobs/502362010.htm ), a shot polisher and inspector (http://www.stepfour.com/jobs/509485014.htm ), and a shot bagger (http://www.stepfour.com/jobs/920687170.htm ). In the description for the shot dropper, we learn that he is responsible for controlling the temperature of the kettle which hold the molten lead, the rate that the molten lead flows out of the kettle, watching for plugging of the shot plate and controlling the flow of metal to be melted into the kettle. The shot polisher and inspector operates a glass plate sorting machine that separater round shot from out of round shot, screens the shot to obtain the proper size, and sends out of specification material back to the shot dropper to be remelted. Lastly, the shot bagger loads the shots in bags for shipment. There may be higher technology methods to produce shot by chopping wire into short lengths and machining them into round shapes, but dropping molten lead into a stream of cold air is a simple technology that is hard to beat. Thanks for your question. To get some idea http://www.stepfour.com/jobs/502362010.htm rop for Extruding process Federal Cartritge
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