Punches are used when the head of the hammer is too large to strike the object being hit without causing damage to adjacent parts. A punch transmits the hammer’s striking power from the soft upper end down to the tip that is hardened high carbon steel.
A punch transmits an accurate blow from the hammer at exactly one point, something that can't be guaranteed with a hammer on its own.
When some points need to be drawn on an object like a steel plate to help locate a hole to be drilled in it, a
prick punch can be used to mark the points so they won't rub off, they can also be used to scribe intersecting lines between given points. Its point is very sharp so a gentle tap leaves a clear indentation. Its easier now to draw the lines based on permanent marks.
The
center punch isn’t as sharp as a prick punch and it’s usually bigger. It makes a bigger indentation - called a center - that "centers" a drill bit at the point where the hole is required to be drilled.
A lot of components are either held together or accurately located by pins. Pins can be pretty tight and a group of punches is specially designed to deal with them. This is a
starter drift punch - starter because you should always use it first to get a pin moving.
It has a tapered shank and the tip is slightly hollow so it doesn't spread the end of a pin and make it an even tighter fit. Once the starter drift has got the pin moving a suitable pin punch will drive the pin right out, or in.
The
pin punch is available in various diameters. It’s used to drive out rivets or pins.
Special punches with hollow ends are called
wad punches or hollow punches. They're the neatest tool to make a hole in soft sheet material like shim steel, plastic, leather, or most commonly in a gasket. When being used, there should always be a soft surface under the work, ideally the end grain of a wooden block. If a hollow punch loses its sharpness or has nicks around its edge, it'll make a mess, not a hole.
Numbers and letters like the engine numbers on a cylinder block, are usually made with
number and letter punches that come in boxed sets. As with all punches the rules for using them are the same. The punch must be square with the surface being worked on, not on an angle, And the hammer must hit the top squarely.
There are many applications for blind rivets and there is a variety of types and tools for that may be used to do the riveting.
The
concertina rivet gun, which are sometimes called lazy tongs puts larger rivets in heavy materials.
Riveting pliers are convenient for occasional riveting of light materials. The rivet is inserted into the riveting tool which, when squeezed pulls the end of the mandrel back through the body of the rivet. Because the mandrel head is bigger than the hole through the body, it swells out as it comes through. Finally, the mandrel will snap off under the pressure and fall out leaving the rivet body gripping the two sheets of material together.
A typical
"pop" or blind rivet has a body, which will form the finished rivet, and a mandrel which is discarded when the riveting’s completed.
It's called a 'blind' rivet because there’s no need to see or reach the other side of the hole in which the rivet goes to do the work. In some types the rivet is plugged shut, so it's water-proof or pressure proof.
