Fixing an out of true chuck

Trying to drill a hole accurately with a wobbly bit is a pain in the backside. This pain I lived with for several months until I figured out what was wrong. When I bought this eggbeater, I never had such issues, but since I dismantled the chuck for cleaning several months back, I noticed the wobble started.

I will go through the steps I have taken to find a solution. You can also follow these steps when you’re next at flea markets before buying a hand drill. You don’t want lemons because these hand drills aren’t cheap anymore.

The first thing I checked was the bit. I laid it flat on my table and rolled it. There were no irregularities, for good measure I placed it in my drill press and it was fine. So, I crossed that off the list.

Open and close the jaws in the chuck and watch if the jaws open and close evenly together. If not, get a new chuck.

Next unscrew the chuck completely off the threaded shaft and inspect the shaft. Crank the drill and eyeball shaft carefully. Your eyes will pick up any irregularities if the shaft is bent. You’ don’t need any expensive gizmos for this.

Threaded shaft must run true and straight

Next pop out the jaws and inspect the flat milled back that holds the bit. This must be clean, undamaged, and milled perfectly flat. It is highly unlikely that it isn’t perfectly flat, so inspections by eye are close enough. There can’t be any dings.

By now I was frustrated and I mean really frustrated. I checked everything I could check, and they all passed with flying colours, but did I. There was one last thing I didn’t notice when I put the darn thing back together again. Since I don’t know the part name, the two pictures will give a better picture of what I’m referring too.

Incorrectly seated
Correctly seated

That’s right folks, that part that I’m pointing too was flipped the wrong way round. The bit rests in the cylindrical depression you see in the middle, which aids in keeping the bit centred (centered for the yanks) coupled with the jaws holding the bit in place. These two combined aid the drill bit from wobbling whilst drilling. Amazing, isn’t it? Something that’s so easy to miss can lead to months and months of frustration and hair loss.

7 thoughts on “Fixing an out of true chuck

  1. I disassembled my Miller’s falls’ chuck last night after I saw your post.
    I checked the runout on the shaft with an indicator, deburred and stoned all the edges and gave everything a good clean.
    The chuck is still wobbly.. 😐

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    1. Hang on a sec. Is this a typo error or did you say the chuck is still wobbly? If it is then the shaft is bent. You said you checked it but there could be nothing else. Also when you said you stoned all the edges, I am not sure as to what edges you are referring to.

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      1. My chuck design is quite different. The jaws have parallel faces that are guided in the chuck’s body. Lots of edges. Deburring these made the chuck very smooth. I took pictures but can’t seem to post them here. Maybe I’ll write a blog post about it.
        Total indicator runout on the chuck is 0.1 mm. Although I don’t have any reference to say it’s good, I can’t see it by eye.

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