• Carlie Sitzman MA, CT

Words with Hidden Meanings in Manufacturing Terminology Part 1

Turning, Extrusion, Rolling

There are a number of seemingly normal, everyday words that take on completely different meanings when used in manufacturing or metalworking settings. This can make manufacturing terminology a bit confusing for laymen and might seem almost comical from an outside perspective. Today, I will take a closer look at some surprising terminology used for the manufacturing processes turning, extrusion, and rolling.


Turning (German translation: das Drehen)


Turning is a machining process during which material to be cut (workpiece) is fastened into a special clamp (chuck) that rotates rapidly around an axis. A cutting blade mounted on a semi-stationary arm is moved toward and away from the rotating workpiece in a controlled manner for the purpose of carving out the desired cylindrical shape. This is reminiscent of a person shaping a vase on a pottery wheel, if the wheel were positioned vertically, the column of clay were replaced with metal, and the person’s hands were replaced with a cutting blade. The machine on which turning operations are performed is called a “lathe”.


1. Chuck (German translation: das Drehfutter, das Spannfutter)


Within the context of turning, a chuck is a special clamp used to secure workpieces. Chucks can take on many forms, but they often look like a very thick disc three or more pincers at the center. The clamping mechanism of a chuck mirrors that of the drill bit fastener in a power drill. Pincers can be moved inward to tighten on the piece or outward to release it. The chuck is affixed to the turning mechanism on a lathe and rotates the workpiece once the machine starts up.


2. Dog (German translation: das Drehherz)


In manufacturing and machining, a dog is a type of clamp used on lathes. It is utilized only during a process called “between centers” turning. During this process, the workpiece is suspended between two centered shafts. Since one of the shafts is secured in the chuck and both shafts are centered, neither of them will cause the workpiece to rotate at the same speed as the chuck. The dog clamps onto the workpiece between the shafts and attaches to the chuck. When the chuck rotates, the dog transfers the circular motion of the chuck to the workpiece, thus causing the workpiece to rotate at the same speed.


3. Facing (German translation: das Plandrehen)


For metalworking applications, the word “facing” is sometimes used in relation to turning on a lathe. Facing is the process of moving the cutting blade over the very end of the workpiece as it rotates in order to create a refined, flat finish.


4. Threading

(German translation: das Gewindedrehen, das Gewindeschneiden)


Threading is a process performed on a lathe. It involves moving the cutting tool along the rotating workpiece in such a way as to create the typical groove pattern on a screw shaft that forms the so-called screw “threads”. These threads are a main feature that differentiates a screw from a nail.


Extrusion

(German translation: das Strangpressen, die Extrusion)


Extrusion is when metal is loaded into a chamber and pushed out a small opening in the chamber using a sort of plunger. This process is similar in nature to the procedure of squeezing toothpaste from a tube. The aim is to achieve a rod with a cross section mirroring the shape and size of the opening in the chamber.


5. Butt (German translation: der Stumpf)


When used within the context of manufacturing, the term “butt” is sometimes associated with extrusion. When metal is extruded, a little bit is always left in the chamber at the end. This extra piece is aptly termed the “butt” and usually has to be cut off once the extrusion process is complete.


Rolling (German translation: das Walzen)


In manufacturing, rolling is a process by which the material to be shaped (workpiece) is rolled between two rollers to flatten it. This is similar to the process used to flatten balls of freshly made pasta dough, but with metal instead.


6. Bloom (German translation: die Bramme, der Vorblock, der Walzblock)


Since metal is a very stubborn substance, it usually has to be rolled several times before the desired thickness is achieved. A bloom is one of these intermediate shapes, achieved after the first pass through the rollers.


7. Soaking (German translation: das Ausgleichsglühen)


When metals are rolled, they are sometimes heat-treated beforehand. Basically, this means the metal is heated up before it is fed through the rollers. Not only does heat treating make the workpiece easier to roll without damaging the metal, but it also changes numerous other characteristics of the metal. This happens because, when metal is heated, the molecules inside the material begin to rearrange themselves. To ensure the finished metal product has a uniform material consistency, the molecules must be given time to rearrange at a certain temperature and come to rest in their new configurations. This is what the soaking stage is for. During soaking, metal is gradually brought up to the desired temperature, then held at that temperature until the desired molecular structure has taken shape within the workpiece. It’s kind of like giving instructions to a large crowd of people. You have to leave time for everyone to follow your instructions and scurry to their designated positions before you move on to the next step.


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