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Keyless Chuck Loosening Problem.

I use a Hitachi DV 18DGL battery drill for a lot of my work. It is very good and the battery lasts a long time and charges up quickly when needed.


BUT, when in use the keyless chuck comes loose and the drill bit does not turn due to a poor hold. I have two of these drills and the same problem exists with both chucks. Is it a design problem or a bad batch of chucks? I do not know. Other makes of keyless chucks that I have used over the years hold the drill bits securely and do not come loose even if using a hammer action.


Is there a solution? Perhaps I should pour some fine sand into the chucks.


Z.
Parents
  • You called!


    There is a phenomena machinists call 'chuck walk'.  If the chuck is off axis to the work piece rotation (drill bit) as it turns the radial pressure increases and decreases on the tip of jaw 1 as it turns.  Similarly the pressure at the base of jaw 1 decreases and increases (out of phase).  This effect also happens to the other jaws at 120 degree phase.  The result is the work piece 'walks' out of the jaws or the threaded ring 'walks' against the jaws as it is an inclined plane it's easier for it to loosen than tighten.  Pretty soon something unpleasant happens.


    The solution is to re-grind the jaws (easy if you have a lathe or tool grinder, doesn't everyone?) or buy a new chuck.


    Dave Newton.
Reply
  • You called!


    There is a phenomena machinists call 'chuck walk'.  If the chuck is off axis to the work piece rotation (drill bit) as it turns the radial pressure increases and decreases on the tip of jaw 1 as it turns.  Similarly the pressure at the base of jaw 1 decreases and increases (out of phase).  This effect also happens to the other jaws at 120 degree phase.  The result is the work piece 'walks' out of the jaws or the threaded ring 'walks' against the jaws as it is an inclined plane it's easier for it to loosen than tighten.  Pretty soon something unpleasant happens.


    The solution is to re-grind the jaws (easy if you have a lathe or tool grinder, doesn't everyone?) or buy a new chuck.


    Dave Newton.
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