This is an easy fix. it designed to come of easily and can fall off if you dont tighten the side handle. the chuck has a quick release mechanism. place the chuck onto the machine as far as you can. it wont go on all the way. simply pull back the black collar on the chuck toward the front of the chuck and push the chuck on the rest of the way. to ensure that it is on correctly, turn the chuck by hand until it locks into place. Hope this helps.
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This is an easy fix. it designed to come of easily and can fall off if you dont tighten the side handle. the chuck has a quick release mechanism. place the chuck onto the machine as far as you can. it wont go on all the way. simply pull back the black collar on the chuck toward the front of the chuck and push the chuck on the rest of the way.
to ensure that it is on correctly, turn the chuck by hand until it locks into place.
Hope this helps.