A drill press requires some occasional maintenance to ensure that it continues to run smoothly and drill precisely. If you don't take care of your machine, you can eventually develop damaging rust on the table, run-out and wobble with the quill (which drives the chuck of the drill press and more. By checking a few key areas periodically, you can keep your unit running smoothly and drilling precisely.
Most drill presses use a belt and pulley system for transferring power between the motor and the quill. The entire system is housed in a compartment within the head of the drill press.
Before removing the head cover, unplug the power cord from the electrical outlet, and check the condition of the power cord. Make sure that there are no cracks in the insulation of the cord, and check to see that it is solidly connected to both the plug on the end of the cord and into the motor housing on the back of the drill press. If any damage is present, consider having the cord replaced.
While you're at it, check the condition of the switch on the front of the drill press. There should be no excessive play within the switch, and it should consistently and easily turn the motor on and off. As with the cord, if your switch is damaged, as on other tools, the switch should be replaced.
With the electrical cord unplugged, open the head cover on top of the drill press. Begin by visually inspecting the condition of the belt between the two pulleys. If the belt is worn or is displaying cracking or fraying, replace it with a new belt.
Next, rotate the belt slightly on the pulleys and inspect each of the pulleys fore and aft for any damage or cracks. As with the belt, if a pulley is damaged, it is better to replace it then to continue to use a damaged part.
There are two predominant styles of drill presses: those with multiple pulleys fore and aft (for controlling the speed of the chuck), and those with a single pulley on the motor and quill shaft that employ a variable speed control. In the case of the former, to adjust the speed at which you drill, you'll place the belt on different corresponding sets of pulleys. When you use a larger motor pulley with a smaller quill pulley, the drill chuck spins faster. Conversely, using a smaller motor pulley and a larger drive pulley results in a slower RPM rate for the chuck. Most units of this type will have a chart within the head cover that shows the RPM rate for each corresponding set of pulleys.
If your unit is a multi-pulley system, you should find a small set-screw on both the drive pulley and the quill pulley. Tighten each set screw with an Allen wrench to ensure that the pulleys are securely fastened.
One final step before moving on is to check the tension of the belt. If you squeeze the belt together centered between the pulleys, you should have less than 1/2-inch of deflection. If your belt deflects more than 1/2-inch, check to see that the belt tensioning unit is clean and working properly. You may need to tighten the mounting screw to give the tensioning unit a bit more strength.
If your drill press does not have a tensioning unit, you can loosen the motor mounts with a wrench and slide the motor rearward to place more tension on the belt. Be sure that all of the motor mount bolts are fully-tightened before turning on the drill press.
Check the Quill Tube
Once you know that the pulleys and belt are in good working order, move onto the quill. Remove the chuck and set it aside for the moment. Grab onto the exposed lower end of the quill and move it laterally in any direction, checking for play between the quill and the quill tube of the drill press housing. A loose quill will cause some wobble of the chuck when the drill press is operating, which can cause imprecision. This is especially problematic when using very clean drill bits such as a forstner bit or a sharp-pointed bit such as a spade or auger bit.
If you find that your quill has some wobble, you should be able to tighten the mounting bolt that secures the quill tube into the motor housing with a wrench to reduce or even eliminate the wobble. Then check the quill again for looseness before replacing the chuck.
Clean the Table
Most drill presses come with a solid table, often made from cast iron. While such a table provides a very solid platform from which to work, it is also very susceptible to rust. You can clean the table much like you would that of a cast iron saw table, then protect it using a rust-resistant protectant such as Boeshield T-9. If you allow the rust to remain on the table, it can affect the ability to finish many fine hardwoods and even sanded plywood. By keeping it clean, not only will your table last longer, but your projects will avoid damage from a rusted table.