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Learn Mechanical Engineering at Home Series – Punches and Drifts

written by: Ricky • edited by: Lamar Stonecypher • updated: 11/19/2008

Have you ever wondered what mechanical engineering is all about? I cannot make you a certified mechanical engineer but certainly you can learn a lot about mechanical engineering by reading this Learn from Home series on mechanical engineering.

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    Introduction

    Punches and drifts of various types of extensively used in the mechanical engineering workshop and this article discusses about a few basic types of punches which are commonly including center punch, drift punch, pin punch and so forth.

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    Punches & Drifts

    Center Punch

    The shape of a center punch is somewhat similar to a ball pen and it is made out of cast steel. The tip of the punch is given a nice conical shape while the handle is knurled to provide a grip during its use. The main use of a center punch is to make small points which act as markers during operations such as drilling. If you want to drill at a particular place on a workpiece it might be difficult to do it manually unless there is already a tiny dent or mark to guide the drill and prevent it from going astray, and this is achieved by lightly striking the punch with a hammer after keeping it above the requisite point.

    There could be several other uses to which the punch can be put depending on requirement. For example if a bolt or screw has broken while being loosened and the remaining part is almost embedded entire inside the workpiece it could be extracted by punching a small hole on the broken cross section of the screw and using a hammer to give it a rotary motion slowly but steadily.

    Another use could be to mark certain parts which are being disassembled so that their relative direction or position can be gauged correctly when it is being boxed back.

    Center Punch  

    Pin Punch

    This punch has a parallel shank end and does not have a pointed end like a center punch but instead a flat base. The main use of such as punch is to remove pins from a chain provided the diameter and the length of the shank are compatible with the pin dimensions. Normally the diameter of the punch needs to be slightly less than that of the pin and the pin hole and the chain links need to be kept on a surface which is hard but has a hole beneath the place where the pin would slip out.

    A closely related cousin is the drift punch which differs from the pin punch in that it has a tapered shank rather than a parallel one. As the name suggests it is used to drift out tapered pins from work pieces.

    Pin Punch  

    Key Drift

    This can be said to be a special type of drift punch and has a peculiar tapered shape as can be seen in the diagram. The main use of this punch is to remove keys between a shaft and the wheel or gear mounted using that key. The picture below shows both the side view and the plane view of a typical key drift

    Key Drift  

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