Tighten the screws

Hold your screwdriver to a higher standard and you'll get greater performance and quality.

Using the right screwdriver for the job can be compared with wearing a loose glove vs. a tight glove.  The glove’s fit and feel greatly affects the grip and ability to get work done. The same is true for screwdrivers, say industry experts.

“A screwdriver bit should fit the fastener’s head recesses as completely as possible. It should not be shorter or thinner than the fastener for best results,” says Alan Anderson, supervisor of product engineering at Cooper Hand Tool’s Sumter, South Carolina, plant.

Tight fit for torque transfer

“The whole object of the screwdriver’s design is to transfer torque, or turning force, from the user’s hand and into the screw. The mechanical connection from the hand to the screw must be as tight as possible. If it fits snug, it won’t wobble. The tip must fully fit the length and the width of the fastener head to fully transfer the load to the screw face. If the head is thinner and narrower than the screw face, it is more likely to slip out of the head and cause work piece damage or user injury,” Anderson says.

Over time, screwdrivers tips wear and, based on the tool’s quality, can wear out much sooner than expected.

“The old adage, ‘You get what you pay for,’ is certainly true for screwdrivers,” says Alan Sipe, senior vice president of sales and marketing at Klein Tools, Inc. “Think about it: an electrician may make almost $40 an hour, but if he or she is trying to work with a $3 tool that makes the job harder and take longer, where is the economy in that? A high-quality screwdriver costs $6 or $7 while an inexpensive one may cost $3. The difference in productivity for the worker makes up the cost differential very fast,” he says.

To achieve the best fit for the job, Sipe and Anderson agree the tip must precisely fit the head. Failure to do so will damage the screw head and even the screwdriver.

Phillips screws and screwdrivers are the most misused, says Anderson. “Workers often try to get by with the wrong-sized screwdriver for the Phillips head,” he says. “That is a mistake because the Phillips style head is a brand that requires careful machining to reach the proper tolerance to maximize driver/screwhead contact. It should fit so the tip and head act as one.”

Phillips screw head sizes are designated as zero, which is the smallest, to four, which is the largest. “Typically, you will find the zero head screwdrivers on a 1/8" shank; a No. 1 head on a 3/16" shank; No. 2 on a 1/4" shank; No. 3 on a 5/16" shank and a No. 4 on a 3/8" shank,” says Anderson,

“Many screwdrivers have the tip style stamped on the head of the handle so users can pick the right screwdriver quickly and easily from their tool pouches while working,” says Sipe. Klein takes that one step further by indexing or lining up the tip of the screwdriver with the Klein’s Tip-Ident marking on the end of the handle of the tool. This allows the user to align the tip with the handle end in tight places.

While standard and Phillips-style heads dominate the fastener industry, several other head types are gaining acceptance. “The Torx and the Robertson heads are gaining popularity,” says Sipe. “We are seeing deck builders and electrical companies adopting the Robertson head, which is similar to Torx. These multi-sided designs offer an exacting fit. They fit so tightly that you can put the fastener on the tip then reach into the work piece without the fastener falling off the tip,” he says. The multiple sides also improve torque transmission so more force can be exerted without cam-out.

Screwdriver design

Screwdrivers have three components: The handle, the shaft and the tip. The component’s quality reflects the tool’s overall quality.

A variety of handle designs have been introduced over the years, claiming ergonomic features and benefits. However, the ribbed handle remains the most popular.

“Powered drill/drivers are used in highly repetitive fastening and screwdrivers are mainly used for small jobs at hand,” says Sipe. “Even with ergonomic designs, users aren’t experiencing great fatigue from repetitive work.”

However, the tri-lobe design has its fans. “We have tested the tri-lobed design and users find it offers the most torque transfer,” says Anderson, “The screwdriver should offer a comfortable grip where you don’t feel the hard edges while you are gripping it.”

Handle materials must meet demanding specifications set out by the American Society for Testing and Materials (ASTM). It requires screwdriver handles to perform at temperatures greater than 125 F yet not shatter or break at below-freezing temperatures.

While the translucent plastic handle style is an ever-popular choice, co-molded handles, where the solid, cellulose handle has softer durometer material incorporated into it, improves comfort and grip. “The cushion-grip design varies across brands, and it improves the user’s grip so torque is transferred more efficiently,” says Anderson.

The shaft can speak volumes about the tool’s quality, the experts agree. “Shaft finish is a good indicator of quality. The smoother the finish, the higher quality the tool,” says Sipe.

Go for uncoated tips

Both experts agree that the highest-quality screwdrivers have coated shafts and uncoated tips. “The chroming or coating process pulls heat treatment from the metal, which is important to tip durability,” says Sipe, “The tips should be profiled or machined, not stamped or swaged, especially on Phillips screwdrivers.”

“The Phillips fit is very exacting and a screwdriver carrying the Phillips name pays a license fee and must meets exacting tolerances,” adds Anderson. “Screwdrivers that are stamped or labeled as cross-cut screwdrivers won’t fit as precisely and are more likely to cam out of the head under torque,” he says.

The blade or tip finish should be consistent and free of chips and nicks. Dents or scratches are imperfections that can point to an inferior tool,” Anderson adds.

For even greater control, some Phillips screwdrivers have horizontal ribs etched or machined across the flutes. “These anti-cam-out ribs (ACR) create greater frictional forces against the screw head for greater torque transfer,” says Anderson.

Some screwdriver styles incorporate helpful tools. “We offer a screwdriver with a spur at the top which allows the electrician to catch a stripped wire end and bend it into a perfect loop for connecting to a fixture. It doesn’t affect the tool’s strength and adds versatility,” Sipe says.
 

Screwdriver use tips Screwdrivers are single-purpose tools that end up being used incorrectly for many jobs. This can greatly shorten their useful life and even make them dangerous to use. Here is what the experts suggest to get the safest and most productive use from your screwdrivers: They aren’t chisels, so don’t use them that way. Although screwdriver tips are hardened, they aren’t engineered to take extreme forces across the face of the tip from striking which will damage or bend the tip. “Using a screwdriver as a chisel is torture on the tool,” Sipe says. Don’t use them as a punch or pry bar. While that thin tip can mimic the actions of a pry bar, it can’t take the forces from using the tool as a lever. “A screwdriver can fail under these stresses. It is not built for it and is it worth the risk to have it break and cause an injury?” asks Anderson. Use the right tip with the right fastener. Standard and Phillips screwdrivers are often pressed into service to tighten or loosen the wrong fastener size. Using the wrong size will lead to cam-out, which strips the head and may even damage the screwdriver blade. Don’t modify tips. If you need a thinner tip, get a screwdriver with the right tip size. Any change in the tool greatly compromises its ability to do the job. Replace the tool when it’s worn or damaged. “The nominal price of a screwdriver isn’t worth the cost of delaying its replacement. Slower work or an injury will offset the cost difference quickly. Quality tools last much longer than low-cost tools, which makes them an even better value,” Sipe says. Use insulated screwdrivers as a secondary protection method. Common screwdrivers should never be used on powered circuits. Electricians may use insulated screwdrivers that allow them to be used on live circuits up to 1,000 volts. “This is a secondary level of protection. Gloves that have an electrical rating are the first method of protection,” Sipe says.

Published in the March 2004 issue of Contractor Tools and Supplies magazine.

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