Latest Info Hot !: How to Drive Screws Like a Pro

The task of driving screws improved exponentially about 30 years ago with the advent of the battery-powered cordless drill/driver. Today, the ubiquitous drill/driver is the go-to tool for virtually every hole-drilling and screw-driving job.

However, to power-drive screws with speed and precision takes practice, patience, and a few tricks of the trade. Here are some tips and techniques to help you maximize the screw-driving capabilities of your cordless drill/driver.

Back Off the Clutch

Every drill/driver has a slip clutch, which is also called a torque control. It's the adjustable collar located directly behind the chuck. The numbers on the slip clutch represent the amount of torque, or twisting power, that the drill produces. The higher the number, the more torque is delivered to the screw head.

Learning to use the slip clutch properly allows you to drive screws to the correct depth, without under-driving them so that their heads stick up or over-driving them right through the board. As you drive in the screw, the slip clutch monitors the amount of torque applied to the screw. If the force required to drive in the screw exceeds the slip-clutch setting, the clutch will disengage, or "slip." At that point, the chuck stops turning, but the drill motor continues to run.

It takes a little practice to know where to set the slip clutch, but it's best to start at a midrange number. For example, if the drill has 30 clutch settings, set the clutch to 15 and then drive in a screw. If the clutch slips before the screw is fully driven, rotate the clutch setting to a higher number. If the drill drives the screw too deeply, adjust to a lower number.

Generally speaking, use higher slip-clutch settings to drive in large, fat screws, and lower numbers to drive small, thin screws. However, you must also take into account the hardness of the material you're screwing together. Driving screws into plywood and softwoods, such as pine, cedar, and fir, typically requires little torque. But, if you hit a knot or particularly gnarly section of wood grain, you'll have to crank up the clutch. Driving screws into hardwoods, such as oak, maple, and mahogany, requires more torque and higher clutch settings.

Bore Clearance Holes

Mastering the slip clutch might be the most important screw-driving skill, but coming in a very close second is learning to drive screws without splitting the board.

The first step is to predrill a hole through the top board that's equal to or very slightly larger than the diameter of the screw shank. This hole, known as a screw-shank clearance hole, permits the screw to pass cleanly through the top board. That's important, because without any friction in the top board, the screw can pull the two boards tightly together.

Clearance holes are particularly important when driving screws close to the end of a board or very close to the edge, where splitting is common.

Drill Pilot Holes

A pilot hole works in conjunction with a screw-shank clearance hole. A pilot hole is a small-diameter hole bored into the bottom board. Its purpose is to provide a path for the screw to enter the board without splitting it. Again, it's particularly important to bore pilot holes near the ends and edges of boards, but they're also recommended when screw-driving into hardwood or any thin board. The properly sized pilot hole will also prevent screws from snapping in half, which is especially important when driving screws made of brass, a notoriously soft metal.

Below is a chart to use as a general guideline when drilling screw-shank clearance holes and pilot holes. Note that pilot holes in hardwood are slightly larger than those for softwoods. These are the five most common screw sizes, ranging from 4 to 12. (The larger the number, the fatter the screw.)

Screw Size: 4
Clearance Hole: 7/64
Pilot Hole, Softwood: 3/64
Pilot Hole, Hardwood: 1/16

Screw Size: 6
Clearance Hole: 9/64
Pilot Hole, Softwood: 1/16
Pilot Hole, Hardwood: 5/64

Screw Size: 8
Clearance Hole: 11/64
Pilot Hole, Softwood: 5/64
Pilot Hole, Hardwood: 3/32

Screw Size: 10
Clearance Hole: 3/16
Pilot Hole, Softwood: 3/32
Pilot Hole, Hardwood: 7/64

Screw Size: 12
Clearance Hole: 7/32
Pilot Hole, Softwood: 7/64
Pilot Hole, Hardwood: 1/8

Countersink vs Counterbore

The most common screw used today to join wood is the flat-head screw. In most cases, you'll want to drive the screw head either flush with the board's surface, or below the surface.

To make the screw head flush, you must use a countersink bit to drill a shallow hole into the board. This is particularly necessary when working with hardwood. In softwood, you can usually drive the screw head flush without first countersinking the board.

If you want to set the screw head below the surface, you'll need to drill a counterbore hole using either a small-diameter spade bit or brad-point bit. Counterbore holes can then be covered with wood plugs (and sanded flush) or decorative wooden buttons.

Use a Combo Bit

You can use individual bits to drill all the necessary holes prior to driving in the screws. Or, you can use a combination bit. With this single timesaving tool you can bore the pilot hole, screw-shank clearance hole, and countersink or counterbore—all in one motion. Combination countersink bits come in various screw sizes (typically 4, 6, 8, and 10) and are sold individually or in sets.