How to Fix Three-Jaw Lathe Chucks

Three-jaw chucks, used for clamping with metal lathes, wear down as a result of years of hard use. The tool is commonplace with machinists working with metal products. When the chucks become worn, the result is the tool being out of "true" -- calibration -- on the lathe. For accuracy in their work, machinists rely on their chuck jaws to be trued, or re-calibrated. Fixing, or truing, your chucks can be done with a few steps.

Work gloves
Protective headgear
Protective eyewear
Metal drill press
Endmill
Cardboard
Pencil
Box cutting scissors
Metal grinder
Fine metal file

Instructions

- 1
  Place the jaws in the chuck as you normally would.
- 2
  Cut a 1/4-thick steel plate to the same thickness as the chuck with an endmill. Load the plate into the drill press and drill a hole at the center of the plate. Align the hole to match the diameter of the hole on the chuck.
- 3
  Place a piece of cardboard at the three jaw holes. Mark the placement for each of the three jaw holes on the cardboard, creating a template for the steel plate.
- 4
  Trim the cardboard to the size of the steel plate with your scissors. Place the cardboard on the steel plate and drill the holes in the plate.
- 5
  File away excess burring caused by drilling. Slide the steel plate in place over the jaws.
- 6
  Re-bore the jaws, with the steel plate in place as a guide, using the metal grinder. The jaws are now fixed or "true".

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