Levels Hot Dogs Abrasive Grains Sandpaper
Today on "how it's made"... Levels... Hot dogs... Abrasive grain... And sandpaper. The level was invented in the 17th century to keep structures plumb and true. Without it, buildings would lean, floors would be crooked, and maps would have inaccurate elevation information. No matter what you're making, this critical tool always gives it to you straight. It's a centuries-old concept, but still measures up. Center the little bubble, and you're perfectly straight. Production begins with a length of laminated birchwood. An automated router carves out several holes, three of which will enclose the vials. The other two will serve as handgrips. Next, it's time to tackle the wood's perimeter. Grooves are cut along the length of the wood for the level's brass binding. Strips of brass are unwound into a forming machine. Rollers iron out the curl from the coiling. Other rollers then crimp the brass. This process will allow the strip to fit into those grooves in the wood. Lengths of brass binding are loaded into a machine that slides them into place. This reinforces the edges of the wood. Over at another station, a machine melts and molds the plastic for the vials. Each one is slightly curved inside so the bubble has a place to sit. The vials wind their way through a vibratory feeder. It takes them to a gripper that rotates each one so the open end faces up. In goes a squirt of yellow mineral spirits, leaving just enough room for a bubble to form. A robotic arm plugs the vials with plastic caps. Then this sonic welder melts the caps onto the vials using high-frequency sound waves. Now it's time for inspection. A tiny camera photographs the bubble and sends the picture to a computer that makes sure the bubbles are the right size. For this production run, the bubble should be about half an inch wide. If it's on the mark, the computer allows the vial to move on. A printer then hot-stamps centering marks onto the vial. But this spirit vial isn't quite ready for business. First it needs to bake for 24 hours. The heat exposes any flaws, and the defective vials are rejected. The vial is illuminated with a bright red light as it slowly spins between rollers. A camera photographs the bubble, and a computer scans the image to check for shifting. Too much shifting could compromise the level's accuracy. The vials that pass the test then go on to a molding system. Melted plastic is injected into the crevices to make a cradle for each vial. Next, a technician glues the cradled vials in the openings in the wooden framework. This is precision work. Each vial has to sit perfectly level, so technicians rely on a magnified image to check their progress. Some vials are installed vertically to gauge if the walls are plumb, while the horizontal ones let you know if the floor is level. Acrylic-rimmed windows are fitted over the vials to protect them. Rubber caps are screwed on to both ends of the level. And finally, the trademark stamp goes on. These levels are now ready to straighten up any jobsite. When we return, the real skinny on an all-american favorite. Hot dogs are an all-american fare. But most likely it was german sausage makers who first came up with the idea. In fact, there are reports of german immigrants selling them from pushcarts in new york's bowery as far back as the 1860s. A century and a half later, hot dogs are still the number-one treat on the street. Traditional hot dogs are made from a mix of pork, beef, and chicken. The cuts they start with are called trimmings-- pieces of meat left over from cutting steaks or pork chops. The trimmings are ground the same way butchers chop up hamburger meat-- by pushing the cuts through grated metal plates. Processed chicken trimmings are added to the ground meat, followed by food starch, salt, and other flavorings. These flavorings vary depending on where the hot dogs are to be sold because people in different regions have different tastes. Water is sprayed into the mix, and everything is blended together in a big vat. Corn syrup adds a dash of sweetness. The addition of even more water helps to disperse the ingredients and make the hot dogs juicier. Another machine then purees the meat batter into a fine emulsion and vacuums out any air. Long rolls of cellulose tubing are loaded into the stuffing machine. It pumps the meat puree into these casings, twisting it every 5 1/4 inches-- the length of one hot dog. It takes just 35 seconds to make a chain of hot dogs that would span a soccer field twice. Then three of those hot-dog chains are linked together to make an even longer string, and they're loaded several at a time into another machine, which drapes the hot dogs onto moving racks. The process is carefully timed so that a twist always lands on the bar. The racks shunt the hot dogs through a liquid smoke shower, then into an oven with several cooking zones. The liquid smoke seeps through the casing and adds flavor to the dogs as they bake. Hot out of the oven, these franks are drenched in cold, salty water to chill them in preparation for packaging. The hot dogs then file down to an unloading zone. Here, a machine pulls them off the bars onto a conveyor. Then the hot dogs slide off the conveyor into metal containers. If you've been wondering about those black stripes on the casings, all is about to be revealed. The stripe is a marker attached to the casing. The absence of a black stripe means the hot dog is cooked and ready for packaging. Inside the peeler machine, a tiny knife slits each casing along the top. Then steamy air blows the casings right off the dogs. This machine peels 700 hot dogs a minute. An inspector makes sure the casing has been completely removed and that there are no defects in the dogs. Then it's into a device that looks like a plastic bicycle chain. The sprockets position the hot dogs for packaging. This factory manufactures an incredible 300,000 hot dogs an hour. That's close to 2 1/2 million per shift. They really do churn them out like sausages. Fire up the grill, and a mouthwatering meal is just minutes away. Up next, the hot scoop on abrasive grains. It takes true grit to make sandpaper, as in abrasive grains. People have been using abrasive minerals to sand and polish things for centuries. Today, these minerals undergo heavy processing to make the grade, from very superfine to very coarse. Whether you're working on metal or wood, the right grade of abrasive grit is essential for finishing the job. The factory starts with bauxite, a naturally occurring mineral that resembles clay. They add alumina, a white powdery material that's actually derived from bauxite. The bauxite and alumina are blended with other minerals, then released into an electric arc furnace. Here, three large electrodes use intense electrical current to heat the mix to over 3,600 degrees fahrenheit. That's hotter than an active volcano. In fact, the mixture looks a lot like lava as the minerals melt and blend together. Standing well back and using a long ladle, a technician takes a sample for chemical analysis. If the mix is right, the molten minerals are emptied into a big steel pot. The searing liquid weighs several tons, so a crane is needed to transport it to a cooling area. 24 hours later, with the material hardened, it's time to bring in the wrecking ball. It cracks open the hardened concoction, which is still quite hot at the core. The wrecking ball is dropped repeatedly to break up the hardened minerals. Next, the lumps of abrasive material are transferred to a conveyor system. Metal-plated crushers break them up into fist-sized chunks. A magnet picks up any excess iron. And then it's into the roll crusher, where iron cylinders grind the chunks to bits. Workers assemble screens in decreasing mesh sizes to make a kind of shaking sieve. It sifts the mineral particles through the screen with largest mesh first, then continues to sort the grits in progressively smaller sizes. For some perspective, we placed a quarter against the various mesh sizes. As you can see, only the finest particles could pass through tightest weave. The bits of grit bounce across the screens and fall into hoppers--  a different one for each size. The coarsest grains will be used for rough-sanding jobs. The smaller the grain, the finer the finish. The finest grits are virtually microscopic. The next step is to inspect the grain's shape. A sample is funneled into a cup. Then it's weighed. A higher weight means the bits are densely stacked and therefore blockish in shape with blunt edges. A lower weight means they're flat and sharp. A different test is used for the most minuscule grits. The particles are suspended in an an electrolyte solution. Then an electrical charge is applied. This allows inspectors to count and evaluate the grits via computer. Now these abrasive grits are ready to be packaged and shipped out. Coming up, we'll go to the sandpaper factory, where the abrasive grits meet their ultimate destiny. We'll have the nitty-gritty on that process next. To make sandpaper, you need a lot of grit. There are thousands of tiny abrasive grains on a single sheet. The whole idea is to create friction. By rubbing the sandpaper against wood or metal, you can remove defects and create a uniform surface. It's ironic that something so abrasive can make things look so smooth and polished. Sandpaper often isn't made from paper at all, but fabric like poly cotton. The cloth is unwound into a machine with a printing press. Rollers lined with rubber printers stamp product information onto the cloth. The cloth then travels underneath the printing press, where more rollers apply a heat-setting adhesive to the unprinted side. A computerized system measures the density of the coating to ensure that it's been applied correctly. Then the cloth is pulled one floor down to the electrostatic pit. Here, the environment is kept hot and humid-- perfect for applying abrasive grains to the cloth electrostatically. The grains are poured onto a conveyor belt in the pit. The conveyor moves the grains under the rolling cloth and between electrodes and ground plates. The system generates an electrical field that triggers a mini sandstorm. Once airborne, the abrasive grains stick to the adhesive-coated cloth and become embedded in it. This method allows for even distribution of the grains across the cloth. The grain-coated cloth now rolls out of the pit and back up to the main level of the factory. A technician cuts a swatch of the sandpaper, then peels away layers and makes three different cutouts-- one of the cloth alone, another of the cloth with the adhesive coating, and a third, the grain- and adhesive-coated cloth. He weighs each cutout to confirm that the sandpaper has been formulated precisely to specification. He also examines the gritty surface under a microscope to make sure the grains are standing up evenly. This production run gets the go-ahead, so workers move the sandpaper through a hundred-yard-long oven. It has three different heating zones, each progressively hotter. The increasing heat bakes the grains into the adhesive. The sandpaper is now rough enough, but it's not quite ready for use. In the next step, a coat of resin is rolled over the gritty surface, binding the grains to the base. After the resin is cured to the surface, these jumbo rolls of sandpaper are stored in a warehouse until it's time to cut them down to size. Some rolls are sliced into big sheets. These will be made into commercial sanding belts-- the kind used in heavy manufacturing. Another machine punches out sanding discs. And at this station, four rolls of sandpaper are simultaneously unwound into a machine. It carves the four layers into rectangles. These rectangles won't be used for sanding, but as grip tape for skateboards. From refinishing your furniture to nose-grinding at the skate park, sandpaper will always give you an edge. And with so many grits to choose from, there really is a sandpaper for every job.