Anatomy of a Screw
A handheld screwdriver and muscle power used to be the only option for driving screws. The development of a spiral ratchet driver made things easier, but not nearly as much as the development of electric and, more recently, cordless drills.
Drive Designs and Drivers
The three basic screw-drive designs are shown above. The slotted screw was first on the scene. Once screws became standardized, slots did, too, and screwdrivers followed suit. Next came the square drive, developed by Peter Robertson in 1907. The corresponding driver was crafted for an exact fit — within 1,000th of an inch. In 1937, Henry Phillips was granted a patent for his cruciform recess design, which also has a firm fit.
When drilling the clearance and pilot holes and the countersink in hardwoods, three bits (shown below, top) are required. In softwoods, a tapered-bit-and-countersink combo (below, bottom) can be used.
Devices such as Rockler’s Insty-Drive System let you move fast without re-chucking.

The anatomy of the wood screw changed little in the hundred years after Cullen Whipple of Rhode Island was granted a patent in 1849 for putting a gimlet point on what had been a blunt-ended screw to make a self-starting wood fastener. But the past 50 years have seen the development of a variety of head types, shank types and thread types — though all work according to the same principles as the standard wood screw.

As shown in the illustration at right, a screw is a cylindrical wedge with a winding thread wrapped around it. It’s used to join two pieces of wood or something else to a piece of wood, as in the case of attaching the leaf of a hinge to a cabinet door. The piece closest to the head of the screw is the captive piece, and the piece in which the thread of the srew becomes embedded is the anchor piece. As the head of the screw seats in the captive piece and the top edges of the helical thread become embedded in the anchor piece, the pieces are pulled together tightly.

In driving a screw, the aim is to seat the screw without causing damage to its slot or recess. This damage is called cam out, and the key to preventing it is to exert sufficient pressure to keep the driver engaged and control the speed of driving so that you stop when the screw is seated.

You want to avoid cam out because the screw head might become stripped, making the screw difficult to remove without a special extractor bit. A mashed-up screw head is a sorry sight, as well.

One of the keys to avoiding cam out is proper preparation of the material to be joined by the screw. This involves boring a pilot hole in the anchor piece and a clearance hole and a countersink in the captive piece so that the head of the screw will sit flush to the surface when driven. For best results, the clearance hole in the captive piece should be large enough for the screw to freely pass through, and the pilot hole in the anchor piece should be the diameter of the core of the screw, not including the thread.

For hardwoods such as maple, oak, and cherry, three different bits are required to make a countersink, a clearance hole and a pilot hole. If you are going to drive a brass screw into hardwood, it’s good practice to drive a steel screw into the hole first to avoid breaking the softer brass fastener.

In softwoods, a tapered-bit-and-countersink combo works well. The latest and greatest option is a system that combines multiple drives, taper-countersinks or even self-centering bits.