3 Jaw Chuck troubles

[Toolles]

My dad has a 3 jaw chuck, brand unknown, that is very hard to operate. I have never had one apart and can't tell him what to do to fix the trouble. Can anyone help me with what to expect when tearing into a chuck?
toolles

 

[Cuda]

More than likely it's just filled with fine chip dust, often you can just remove the jaws and clean the scroll under the jaws and the jaw teeth, if that don't work you have to take it apart and clean it all real good, it's very simple to do, make sure the jaws are numbered or marked so they can be reinstalled in the same slot, when putting it back together you usually install #1 jaw first, it will have a tooth closest to the point then rotate scroll until #2 jaw catches the scroll and then #3.

 

[redlee]

3 Jaw chucks are really simple to take apart and clean, just look at it and see how its put together, remove your jaws, remove backplate if it has one , then usually 3 screws to remove the back plate- sometime you can use the screws to tap it apart. Remove the pinion retaining pins and slide the pinions out, remove the scroll plate- I use a flat piece of Alum. or wood to tap out the scroll plate. I also mark the chuck halves to put it back together the same way.