Know-How Notes: Punch & Chisel Guide
Working on your own vehicle means having a lot of different tools, going far beyond those found in the typical tool kits and kitchen drawer. When it comes to specialty tools, there are many different types and uses, using the wrong one can not only damage the tool, but it can make your project take longer than necessary. Punches and chisels certainly fit in that category. Some of the difference in punches are very subtle, but it makes a difference in the effectiveness of the tool.
Punches are available in singles or as part of a kit. Buying a kit is the best way to go for most DIY hobbyists, as you get an assortment of the most commonly used punches (and chisels depending on the kit). Knowing which one to use when is an important piece of knowledge to have. Punches are classified by the shape of the tip. The most common are Prick, Starting, Pin, Aligning, Center, and Drift.
Prick – These punches are used to make light indentations on metal with a light hammer strike. They are not used for making large marks, which can damage sheet metal. These are used in design work, where the punch is used to mark locations on a workpiece directly from a drawing. These are typically used on softer materials like wood, plastic and soft metals.
Center – Similar to a prick punch, the center or starting punch has a sharp tip (typically 60-degrees) that is used to make an indentation in the part to assist in drilling. This keeps the drill bit from walking and helps the bit cut into the part faster.
Taper – The taper punch looks just like sounds, a wide taper running from the handle to the tip. These are designed for starting the removal of pins. The taper gives the punch strength to resist bending. A hammer strike on the taper punch is used to get the pin moving, and then you switch to a pin punch. Taper punches can also be used as aligning punches in many cases. A taper punch should be kept with its corresponding pin punch.
Pin or Drift Pin – Once the pin has been started with the taper punch, the thinner (more delicate) pin punch completes the removal. These punches are thin, designed so that the punch can fully drive out a pin through a long hole. If you try to start the pin removal with a pin punch, you will likely bend it, especially if the pin is stubborn.
Aligning – Similar to taper punches, the aligning punch has a long taper to slide into a hole to align multiple parts through a single hole. These punches are not designed to be struck with a hammer, so don’t.
Transfer – These punches are very useful for transferring the center of one hole to another workpiece. The unique design of transfer punches makes it possible to perfectly center a pilot point for a new hole. The outer diameter of the punch is the size of the existing hole, with a centered punch tip on the inside.
Hole – If you need to make a gasket or template and need a clean hole, the hole punch is what you want. These are typically sold in small packs that include all the common sizes used for DIY projects. Basically you get a punch with a hole in the center and a sharp edge. This allows you to strike holes in gaskets, cardboard, and even thin (very thin) sheet metal without drilling, which usually doesn’t work out to well in thin materials.
Letter – While technically a punch, the letter punch is more commonly referred to as a stamp. When disassembling parts (like and engine) or when marking your tools or equipment, a letter and number stamp set is used. Hold the punch, strike with a hammer and boom, you have a letter or number imprinted on the part.
Chisels are more commonly thought of a woodworking tools, but there are certainly plenty uses for chisels in the automotive world. Woodworking chisels are decidedly different from metalworking chisels. The most common chisels for automotive use are as follows:
Flat – The most common chisel is the flat style. These have a full width edge that is centered on the tool, so that either side of the chisel point has a beveled edge. These are used for busting bolts, chains, and splitting parts.
Rivet – Much like a flat chisel, the rivet chisel has a full-width edge, but unlike the flat chisel, the edge is offset to one side, so that there is a flat cutting edge. This allows the chisel to get under rivet heads to break them apart.
Diamond Point- The diamond point style chisel has 4 cutting edges, instead of a single wide edge. This is useful for cutting holes and V-shaped grooves in metal.
Cape – Essentially a narrowed edge version of the flat chisel, the cape design is not full width of the chisel, rather it tapers to a narrower edge. These are good for squaring rounded corners and getting into tighter spaces where a flat chisel can’t.
Round Nose – These chisels are the opposite of a cape, in that one side is rounded to cut round grooves
Working with chisels and punches requires a deft hand and lots of safety. Holding a punch or chisel by hand is the how most people use them, but it is also the worst way to do it. Instead, spend the few bucks to buy a holder. This keeps your hands clear of the hammer so that your fingernails don’t turn black and fall off after bashing them with a 3-pound sledge hammer. Which brings us to hammers – a striking hammer can be any type, but you typically want a small sledge hammer with a wide head. Dead blow hammers and rubber mallets typically don’t fare well against the hardened steel of a chisel or punch. The smaller the head on the hammer the more likely it is for your strike to glance off the tool and hit you or the part, which is rarely good.
Always practice safe methods when using chisels and punches. All struck tools mushroom on the end over time. These flared edges need to be cleaned up with a grinder so that they do not chip off during a strike or cut your hand during handling. The same goes for your striking tool, if the hammer head is chipped, replace it. Bad things are waiting to happen otherwise.
Check out all the tools & equipment available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on punches and chisels, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.