Process (broaching)

      The process depends on the type of broaching being performed. Surface broaching is very simple as either workpiece is moved against a stationary surface broach or the workpiece is held stationary while the broach is moved against it. Internal broaching is more involved. The process begins by clamping the workpiece into a special holding fixture called a workholder , which mounts in the broaching machine. The broaching machine elevator , which is the part of the machine that moves the broach above the workholder , then lowers the broach through the work piece. Once through , the broaching machine's puller , essentially a hook , grabs the pilot of the broach. The elevator then releases the top of the pilot and the puller pulls the broach through the workpiece completely. The work piece is  then removed from the machine and the broach is raised back up to reengage with the elevator. The broach usually only moves linearly , but sometimes it is also rotated to create a spiral spline or gun-barrel rifling.
      Cutting fluids are used for three reasons. First to cool the workpiece and broach. Second , to lubricate cutting surfaces. Third , to flush the chips from the teeth. Fortified petroleum cutting fluids are the most common , however heavy duty water soluble cutting fluids are being used because of their superior cooling , cleanliness and non-flammability.

Broaching (metalworking)

      Broaching is a machining process that uses a toothed tool , called a broach , to remove material. There are two main types of broaching : linear and rotary. In linear broaching , which is the more common process , the broach is run linearly against a surface of the workpiece to effect the cut. Linear broaches are used in a broaching machine , which is also sometimes shortened to broach. In rotary broaching , the broach is rotated and pressed into the workpiece to cut an axis symmetric shape. A rotary broach is used in a lathe or screw machine. In both processes the cut is performed in one pass of the broach , which makes it very efficient.

A push style 5/16 inches (8 mm) keyway broach; note how the teeth are larger on the left end.

 
      Broaching is used when precision machining is required , especially for odd shapes. Commonly machined surfaces include circular and non-circular holes , splines , key ways and flat surfaces. Typical workpieces include small to medium sized castings , forgings , screw machine parts and stamping. Even though broaches can be expensive , broaching is usually favored over other processes when used for high-quantity production runs.

A broached keyway in the end of an adjustable wrench.

      Broaches are shaped similar to a saw , except the teeth height increases over the the length of the tool. More over , the broach contains three distinct sections : one for roughing , another for semi-finishing and the final one for finishing. Broaching is an unusual machining process because it has the feed built into the tool. The profile of the machined surface is always the inverse of the profile of the broach. The rise per tooth (RPT) also known as the step or feed per tooth , determines the amount of material removed and the size of the chip.  The broach can be moved relative to the workpiece or vice-versa. Because all of the features are built into the broach no complex motion or skilled labor is required to use it. A broach is effectively a collection of  single-point cutting tools arrayed in sequence , cutting one after the other ; i ts cut is analogous to multiple passes of a shaper.

Die operations and types

Die operations and types

Die operations are often named after the specific type of die that performs the operation. For example a bending operation is performed by a bending die. Operations are not limited to one specific die as some dies may incorporate multiple operation types:

Bending:

The bending operation is the act of bending blanks at a predetermined angle. An example would be an "L" bracket which is a straight piece of metal bent at a 90° angle. The main difference between a forming operation and a bending operation is the bending operation creates a straight line bend (such as a corner in a box) as where a form operation may create a curved bend (such as the bottom of a drinks can).


Blanking:

A blanking die produces a flat piece of material by cutting the desired shape in one operation. The finish part is referred to as a blank. Generally a blanking die may only cut the outside contour of a part, often used for parts with no internal features.Three benefits to die blanking are:


1. Accuracy. A properly sharpened die, with the correct amount of clearance between the punch and die, will produce a part that holds close dimensional tolerances in relationship to the parts edges.

2. Appearance. Since the part is blanked in one operation, the finish edges of the part produces a uniform appearance as opposed to varying degrees of burnishing from multiple operations.

3. Flatness. Due to the even compression of the blanking process, the end result is a flat part that may retain a specific level of flatness for additional manufacturing operations.

Broaching: The process of removing material through the use of multiple cutting teeth, with each tooth cutting behind the other. A broaching die is often used to remove material from parts that are too thick for shaving.

Bulging: A bulging die expands the closed end of tube through the use of two types of bulging dies. Similar to the way a chefs hat bulges out at the top from the cylindrical band around the chefs head.

1. Bulging fluid dies: Uses water or oil as a vehicle to expand the part.
2. Bulging rubber dies: Uses a rubber pad or block under pressure to move the wall of a workpiece.

Coining: is similar to forming with the main difference being that a coining die may form completely different features on either face of the blank, these features being transferred from the face of the punch or die respectively. The coining die and punch flow the metal by squeezing the blank within a confined area, instead of bending the blank. For example: an Olympic medal that was formed from a coining die may have a flat surface on the back and a raised feature on the front. If the medal was formed (or embossed), the surface on the back would be the reverse image of the front.

Compound operations: Compound dies perform multiple operations on the part. The compound operation is the act of implementing more than one operation during the press cycle.

Compound die: A type of die that has the die block (matrix) mounted on a punch plate with perforators in the upper die with the inner punch mounted in the lower die set. An inverted type of blanking die that punches upwards, leaving the part sitting on the lower punch (after being shed from the upper matrix on the press return stroke) instead of blanking the part through. A compound die allows the cutting of internal and external part features on a single press stroke.

Die forming

Die forming

Forming dies are typically made by tool and die makers and put into production after mounting into a press. The die is a metal block that is used for forming materials like sheet metal and plastic. For the vacuum forming of plastic sheet only a single form is used, typically to form transparent plastic containers (called blister packs) for merchandise. Vacuum forming is considered a simple molding thermoforming process but uses the same principles as die forming. For the forming of sheet metal, such as automobile body parts, two parts may be used, one, called the punch, performs the stretching, bending, and/or blanking operation, while another part, called the die block, securely clamps the workpiece and provides similar, stretching, bending, and/or blanking operation. The workpiece may pass through several stages using different tools or operations to obtain the final form. In the case of an automotive component there will usually be a shearing operation after the main forming is done and then additional crimping or rolling operations to ensure that all sharp edges are hidden and to add rigidity to the panel.

Die components

Die block
Punch plate
Blank punch
Pierce punch
Stripper plate
Pilot
Dowel Pin
Back gage
Finger stop

Die (manufacturing)

Die (manufacturing)

A die is a specialized tool used in manufacturing industries to cut or shape material using a press. Like molds and stencils, dies are generally customized to the item they are used to create. Products made with dies range from simple paper clips to complex pieces used in advanced technology.

Collet

Collet

A collet (pronounced ) is a holding device—specifically, a subtype of chuck—that forms a collar around the object to be held and exerts a strong clamping force on the object when it is tightened via a tapered outer collar. It may be used to hold a workpiece or a tool.

Nomenclature variations

Generally, a collet chuck, considered as a unit, consists of a tapered receiving sleeve (often integral with the machine spindle), the collet proper (usually made of spring steel), which is inserted into the receiving sleeve, and (often) a cap that screws over the collet, clamping it via another taper.
Usually in shop-floor terminology, the terms collet and chuck are used in contradistinction; users speak of holding a workpiece or tool with either a collet or a chuck. This usage refers to the same distinction as does speaking of using either a collet chuck or another type of chuck (scroll chuck, independent-jaw chuck, etc.); the two usages are different ways of saying the same thing. The difference lies in how one thinks of the overall chain of connection between the machine spindle and the thing being attached to it (workpiece or tool). In general terms, the overall system of holding constitutes a chuck, but practically, the receiving sleeve for a collet is often integral with the machine spindle, and from the point of view of naming the parts that are added on to the spindle, they are either a collet (± cap) or a chuck (such as a scroll chuck).[citation needed]