Page 223 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 7 Bearings, Couplers, Gears, Screws, and Springs 201

FIGURE 7-13 Counterbore bits can be used to create recesses for bearings (credit:
McMaster-Carr).

If you’re working with metal like aluminum, you can use the same method of drilling
progressively larger holes until you reach the correct outer diameter to hold your
bearing snugly. You can also create counterbores the same way as in wood, but most
of the counterbore bits that can handle metal are not designed to work with portable
handheld tools.
The best way to create holes for bearings in metal is to use a drill press or a milling
machine. A drill press is basically what you get when you mount a portable drill on a
stable structure with a base. A milling machine is a fancier version of a drill press that
allows the base to move in the x, y, and z axes so you can do more than just drill
straight down (see Figure 9-4 in Chapter 9). You can use a counterbore drill bit in a
drill press. The best tool to create a counterbore on a milling machine is called an
endmill. An endmill looks like a drill bit with the tip cut off, so it can create holes with
flat bottoms.