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I have a large bench drill on a floor pillar, (see image 1) but one day when i wanted to drill a very fine hole( 3mm) with the same accuracy that you can with this kind of drill, i found that the chuck jaws wouldn't grasp any a drill smaller than about 8mm
so instead of whipping out and buying ( perhaps you can - since it comes with a tool for removing the current chuck) a chuck that would take finer drills, i found another way to do it by salvaging a smaller chuck from a dead portable electric drill
What you will need;
and old power electric drill
( i am sure you could apply the same principle to an old hand drill to)
screw driver to fit the screws on the drill
Step 1: Getting the parts...
1.) First take the old power drill and remove all the screws, and then pry the two halves the drill apart.... It should look a bit like this inside ( image 1)
2.) Locate the two retaining screws for the chuck drive bearing assembly and remove.(image 2)
3.) Then lift the entire assembly out of the drill, you may need to pry the gear wheels a bit. ( image 3)
4.) Now place the entire bearing assembly in to a vice with the chuck hanging down and use a punch and hammer to drive the chuck shaft out of the bearing - make sure you catch it. ( image 4 - hit here)