What is Punch Tool?
A punch is a tool used to indent or create a hole through a hard surface. They usually consist of a hard metal rod with a narrow tip at one end and a broad flat “butt” at the other.
When used, the narrower end is pointed against a target surface and the broad end is then struck with a hammer or mallet, causing the blunt force of the blow to be transmitted down the rod body and focused more sharply onto a small area. Typically, woodworkers use a ball-peen hammer to strike a punch.
A punch tool is a small and narrow piece metal rod featuring a sharp point. A punch tool features a sharp point at the end. The other end of the punch tool features a larger and blunter tip.
To use a punch tool such as this, a worker presses the sharp end against a workpiece, after which he or she hits the blunt end with a hammer or mallet. When the hammer or mallet hits the punch tool, the tool’s sharp end will cut into the workpiece.
Although there are several types of punch tools, most of them use this otherwise basic design. They require the use of a separate tool, such as a hammer or mallet, to “punch” a workpiece.
Hollow vs Solid Punch Tools
Punch tools are often classified as either hollow or solid, depending on their interior composition. Hollow punch tools, of course, have a hollow interior, whereas solid punch tools have a solid interior.
Hollow punch tools are used to create holes in workpieces by puncturing the surface. Solid punch tools, on the other hand, are used to remove material from workpieces or to drive components pins, rivets, etc. into workpieces.
Types of Punch Tools
Mechanical engineering workshops extensively use various types of punches. A few of the basic types include center punch, prick punch, pin punch, and drift punch.
Workshops use punches for locating centers for drawing circles, punch holes in sheet metals, start holes for drilling, remove damaged rivets, bolts, or pins, and transfer the location of holes in patterns. Some punches used are hollow.
Types of punches are as follows:
- Centre punch
- Prick punch
- Solid punch
- Transfer punch
- Drive punch
- Pin punch
- Roll pin punch
- Hollow punch
- Dot punch
- Letter stamps
- Tablet punch
1. Centre Punch
A center punch is used to mark the center of a point. It is usually used to mark the center of a hole when drilling holes. A drill has the tendency to “wander” if it does not start in a recess. A center punch forms a large enough dimple to “guide” the tip of the drill.
The tip of a center punch has an angle between 60 and 90 degrees. When drilling larger holes, where the drill bit is wider than the indentation produced by a center punch, the drilling of a pilot hole is usually needed. An automatic center punch operates without the need for a hammer.
An automatic center punch is a hand tool used to produce a dimple in a workpiece (for example, a piece of metal). It performs the same function as an ordinary center punch but without the need for a hammer.
When pressed against the workpiece, it stores energy in the spring, eventually releasing it as an impulse that drives the punch, producing the dimple. The impulse provided to the point of the punch is quite repeatable, allowing for uniform impressions to be made.
Applications:
The automatic center punch mechanism has been used for a wide variety of other applications. These include
- Marking and starting a hole for drilling without the bit “walking” out of alignment
- Letter stamp sets
- Glass-breaking tools used in rescue work and a common tool for a car thief.
- Impact tool for hardness testing
- Pin presses for electronic assembly
- In many applications, such as hardness testing, the mechanism does not have an adjustment for impulse strength, and may require periodic calibration checks.
2. Prick Punch
A prick punch is similar to a center punch but used for marking out. It has a sharper angled tip to produce a narrower and deeper indentation. The indentation can then be enlarged with a center punch for drilling.
The tip of a prick punch is 40 degrees (the angle depends on what type of prick punch one is using). It is also known as a dot punch. This is also made of high carbon steel; prick punch is also made hard and tempered.
3. Solid Punch
Solid punches are one-piece rod-shaped tools made of metal designed to be struck by a hammer. They are typically used to drive objects such as pins or to form impressions on a workpiece. Solid punches can vary in diameter, length, and tip depending on the job to be performed. Below is a brief description and characteristics of the most common solid punches.
Solid punch is used for boring holes in blacksmith and sheet metal operations. These are used in different measurements according to the jobs. These are produced of high carbon steel, hardened, and tempered.
While using these in hot jobs it is essential to cool them in cold water. These are used in rough works because holes made with a solid punch are not exactly according to measurements and are not clean.
4. Transfer Punch
A transfer punch is a punch (usually in an index set) of a specific outer diameter that is non-tapered and extends the entire length of the punch (except for the tip). It is used to tightly fit the tolerances of an existing hole and, when struck, precisely transfer the center of that hole to another surface.
It can be used, for example, to duplicate the hole patterns in a part, or precisely set locations for threaded holes (created by drilling and tapping) to bolt an object to a surface.
5. Drive Punch
A drive punch is a tool for punching holes in leather and fabric. It is struck with a mallet on top of a cutting board to cut precisely-sized holes into your work. These drive punches are high-quality steel, and they automatically empty themselves of punched material through the side barrel so there’s never any clogging.
For driving out damaged rivets, bolts, and pins that are bound up in holes, you should use the drive punch. The drive punch has a flat face instead of a point. The width of its face defines this type of punch, for example, 1/8-in or 1/4-in. The sides of a drive punch will taper all the way down to the face, but sometimes you may need to use a punch with a straight shank. This is called the pin or drift punch.
In practice, you first use a drive punch to drive the pin or bolt that is to be removed until the hole blocks the progress of the punch.
6. Pin Punch
These types of punches are somewhat different from other punches. It is comparatively larger in length. Instead of being pointed in shape, these are parallel. It is used for tight-fitting pins.
Pin punches can fully turn the rivets and pins out of a hole until they exit the hole, which cannot be done by the other punches. You then use a pin punch to drive the bolt or pin the rest of the way until it is ejected from the hole. Be careful not to use a prick or a center punch to remove bolts or pins from holes, as the point of the punch will spread the object making it even more difficult to remove.
7. Roll Pin Punch
Spring punches also called roll pin punches, are used to drive roll pins. Standard pin punches should never be used on a rolling pin. Because of the hollow, thin wall construction of a rolling pin, a standard pin punch will often collapse, mar, or distort the end of the pin or be driven into, and jammed inside, the hollow core of the roll pin.
When choosing a roll pin punch, select one that is no larger than the compressed diameter of the pin. If a punch is used that is larger than the pin, the surrounding metal in which the pin is seated can be damaged. Also, a roll pin punch should not be used which is smaller than the compressed diameter of the pin. If this occurs, it may be possible to drive the punch through the hollow center of the roll pin.
Roll pin punches are designed with a small projection in the center of the pin tip to support the circumference of the roll pin. The tips of roll pin punches are not flat and should never be used on regular solid pins. If a roll pin punch is used on a solid pin, it will mar or mark the pin.
If the end of a roll pin punch is damaged or deformed, it should be discarded. It is virtually impossible to regrind the tip of the roll pin punch and properly shape the center projection.
When using a roll pin punch, make sure the axis of the shank of the roll pin punch is in line with the axis of the roll pin. Do not can’t the roll pin punch off to one side. When you strike the roll pin punch, hit it directly on the top of its head. If you strike the head of the roll pin punch at an angle you may bend the shank.
8. Hollow Punch
It is a special type of a hardened steel punch with hollowness. It is used for cutting holes in metal, cardboard, fabric. These are available in different sets for holes of different sizes. As they are hollow, the metal which is cut with them falls out through the grooves built on its side. Thus, we can make a number of holes in little time and the holes are quite clear.
Hollow punches make clean holes in gaskets, leather, plastic, rubber, vinyl, and other soft materials, are used for leather craft, clothing, handbags, jacket, webbing, canvas, and for any custom leather works.
9. Dot Punch
The dot punch is similar to a center punch but typically thinner, lighter, and having a sharper tip, used for marking the center of a hole that is to be drilled, or (more generally) for making an indentation in the surface of an object. However, it is more accurate as the dot produced is smaller.
Both the center and dot punches are used in the same way. A ball pein hammer is used to tap the head of the punch and this delivers enough force to the point of the punch to put a small indentation into the surface of the material.
11. Letter Punch
Also known as letter stamps or number stamps, letter punches are used to emboss the impression of a letter or number into a workpiece. They are most common in the reverse image, this allows the end result to be immediately readable, however, they may be made as a positive image.
This is essential in the case of die or mold making and ensures that the finished product will be readable, as a die is a negative image.
12. Tablet Punch
Tablet punches and dies are also known as tablet tools or punch and die tooling, or compression tools. It is essential to have superior quality tablet tools for excellent performance, high productivity, and long tooling life.
A tablet tool determines the uniformity of size, shape, imprint, and weight of the tablets. The die and punches are fit on the tablet press machine single punch tablet press machine or rotary press machine. To make a tablet from powder, the granulated material is metered into a cavity formed by two punches (lower punch and upper punch) and a die.
Then the punches are pressed together with a force to compress the material together in the middle die from opposite directions. With the external pressure of the up punch and the down punch, the materials in the middle die will be compressed tightly.
