Tightening a Loose Chuck

Tightening a Loose Chuck

My faithful old drill press has gotten into the bad habit of losing its chuck at the most inopportune moments. What is to be done to ensure it stays on its seat?

Michael Dresdner: The first step is to clean the mating surfaces of the taper, both male and female. The chuck is held in place by pressure on a two-ended taper – usually a #2 Morse going into the quill, and a shorter, straighter taper going into the chuck itself. If even a small amount of oil, including sebaceous oil from your skin, gets on the taper, it will not hold. Clean the surfaces with naphtha, wipe them dry, and refit the chuck. If it is the larger Morse taper that is falling out, most specialty woodworking outlets and virtually all machinist supply catalog companies sell a plastic cleaning gizmo that does a great job of cleaning the female half of the taper.

After cleaning, pop the taper into the freezer for a bit. That will shrink it slightly. Wipe it off to ensure there is no water on it, and while it is still very cold, set it into the quill or chuck – whichever side has fallen out. Open the chuck all the way so that the jaws are recessed into the chuck body, and place a parallel slab of softwood on the drill table. That will protect the jaws as you press the taper home. Make sure everything (the board, the drill table, and the quill) are at 90 degrees to one another, then pull down on the drill press handle, using the gears to press the chuck into place on the taper, and the taper into the quill, by forcing the bottom of the chuck against the softwood board.

Freezing the taper will shrink it slightly so that when it warms back up to room temperature, the pressure fit will be even more snug.

Lee Grindinger: Try this. Clean the tapered shaft and the tapered bore thoroughly with a solvent such as acetone. Let it dry. Place the chuck in a 300-degree oven for at least a half hour. I’ll caution you that this could get a bit odiferous. Then, using an oven mitt, place the chuck on the shaft and use the pressure of the drill press itself to hold the chuck in place for a few minutes. If neither piece is damaged this will cure your problem. The heat will expand the chuck slightly and as it cools and shrinks it will grip the tapered shaft very tightly.

Posted in: