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On The Tool Truck

On The Tool Truck: Punches & Chisels

Question:  What are the most important punches and chisels for an automotive technician?

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Answer: 

An auto technician is going to use a wide variety of punches and chisels, as is any mechanic in most fields, but there are a lot of overlooked details that are good to know, which will help you buy the right ones and make them last.

Pin punches are exactly that, made for driving out retaining pins of all types. The tips are a consistent diameter and you can get regular or extended length sets, which can be useful for deeper holes. A shorter pin punch is going to naturally be more rigid and provide better control, especially on the smaller sizes, so you may want to use a shorter one to break a pin loose, and once you’ve got it moving, switch to the longer tip if needed.

A variation to these is the roll pin punch, which has a small radiused bump on the end to center the tool on the end of a roll pin. It’s best to use a roll pin punch for a roll pin because if you use a standard pin punch, you can damage the end of the roll pin, making it much more difficult to remove.

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Tapered drift punches are designed to align holes in different pieces of material so that the fasteners can be installed. They are sometimes called alignment punches, and this is in reality all that they are designed to do. By driving one through two holes that are not aligned, the taper will draw the holes into alignment.

A prick punch is one with a very fine tip used to make light markings on metal. These are more commonly used for machining and fabrication when transferring pattern markings, but are very useful to make reference marks on clean metal. Don’t hit them too hard or you can damage the tip.

A center punch is basically a heavy-duty version of a prick punch, and it will make a deep enough mark to allow a drill bit to start without walking. We use center punches frequently to make markings on metal, because generally the deeper mark won’t have an effect on the workpiece, but keep in mind that it does distort the molecules of the metal around it, so if you’re working with thin material, soft metals or the internal components of an engine or transmission, be cautious.

Chisels are designed to remove material with their hardened, sharpened point. The type we use for automotive repair is the cold chisel, named simply because they are designed to remove material and cut cold metal. Having a number of different sizes is useful, and it’s important to remember that the end of a chisel is heat treated. When a chisel begins to dull, you can sharpen it with a hand file, but don’t use a grinding wheel. Getting the end too hot will change the heat treating and it’ll never hold a good sharp edge again.

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The striking end of a chisel or punch is designed with radiused edges to direct the force of the hammer through the center of the tool. If these edges begin to flatten, the force is not directed the same and the ends can begin to split. Dressing these radiuses, also with a hand file, will keep your punches and chisels in top shape.

The best add-ons for a punch and chisel set are a punch and chisel holder, which saves your fingers on a missed swing, and a good pair of safety glasses. You can’t be too careful.

If you have a question for TechShop’s Tool Truck Driver, send an email to [email protected] Your question could be addressed in the next issue of TechShop.

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