Large Drill Conversion to Accept Small Bits




Introduction: Large Drill Conversion to Accept Small Bits

About: Just your average bloke in beautiful New Zealand, solving my seemingly unique problems because I cant find any one else that has.

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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)

Step 2: Result

You should end up with a chuck and two stage shaft similar to that in image 5.

Some times you need to cut a bit off the thinner part of the shaft (away from the chuck - stage b) so that the Jaws of the bench drill clamp around the thicker part of the shaft closest to the chuck (stage a)

So first try it in your bench drill.

If you do need to remove some and don't have a cutting tool capable of doing this hardened shaft, ( like me ) then just grind down the stage (b) shaft only. DON't grind or alter the stage (a) shaft closest to the chuck or you will alter the balance fo the chuck and it will not spin true in the bench drill jaws..

and hey presto you have partially recycled that old power drill and solved the problem....



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    13 Discussions

    If you have a lathe simply turn a rod to fit into your large chuck and center drill a hole for the small bit and install two set screws to run in and lock the shank of the drill from turning.
    The real issue is usually you want higher RPM than the large press can offer with the small bits.

    2 replies

    YEP... if i had a lathe there would be heaps of things i would be doing... IF

    This was something which I was wondering how to do.Cool instructable.

    Well yes you could, at what cost?... hardly the spirit of instructables inventiveness and recycling though is it

    it isnt but i have one right here at my desk so id use that but i would probaly end up making one

    I like the effort in putting up enough pictures to make sense, that's getting a bit of a problem lately with people doing too little effort in that regard, kudos for that, pity they have trouble with the macro though, check out some instructables for making a macro attachment., but they are still good enough to make sense though as they are.

    1 reply

    yes i agree and thank you for the compliment:-) after all the purpose of and instructable is that some one can make it!

    Oh that kind of Macro.... yes i have already taken a new picture to remedy that - the first one was taken in poor light with a cell phone, i must get around to up loading the replacement. But thanks for the macro link - that could come in handy for another project:-)

    Great idea! My drill press is small, but the ones in the shop are huge and won't take small bits. 5/5*