Screwdriver Tips — Literally!
It will never cease to amaze us how the simplest of functions can be so completely misunderstood. Take turning a screw for example. What we always hear is that we should use the right size tool for the task. And we agree. Everyone in the know always advises us to, “Use a screwdriver that perfectly fits the slot in the screw.” But no one ever explains why. We recently learned why, and it’s because we got a chance to spend some time with expert! We were lucky enough to hook up with a man who designs screws.
We got the opportunity to spend an afternoon with John M. “Brad” Wagner, President of Grabber Screws. Brad is an engineer and entrepreneur whose high-end screw company is international in scope. How simple is it? According to Wagner if you use the right size tip the full force of the blade is exerted against the sides of the screw slot and even the toughest screw can be easily tightened (or dislodged). It’s pretty obvious when the blade is too big – it simply won’t fit into the slot. When things really go wrong is when the blade is too small. This is where Brad’s explanation opened our eyes to how a screwdriver tip works in a screw. “If the tip is too small then its sides won’t fully rest against the sides of the screw slot.” He said, “When only the very corners of the screwdriver tip actually touch the slot walls the actual force transferred from the screwdriver blade to the screw itself is almost null.” The more contact there is between the sides of the screwdriver and the sides of the screw slot then the more force will be transferred from the tool to the screw – given that the same amount of force is exerted. Also, if you have to push on the screwdriver handle — as well as turn — then there is a very good possibility that the screwdriver blade is not properly fitted to the screw. Again, the force needed is in the turn – not the push. That’s why keeping a screwdriver tip in pristine condition is really important.
Since you now know that proper fit means more power transmitted from the screwdriver to the screw then it goes without saying that touching up a screwdriver tip to exactly fit the job is crucial. And although this is a task that can be performed with a hand file it is much easier to do when a bench grinder is used. No, we aren’t suggesting that you purchase a bench grinder, but it is easier. And by the way, they are available at most high schools. How do you feel about adult evening education?
Modifying a screwdriver tip to correct damage or to get the blade to exactly fit a particular screw is easy, but there are a couple of things you’ll need to know – first some nomenclature. The screwdriver has three basic parts: 1) the handle, 2) the shaft, and 3) the tip or blade.
• When filing or grinding the very end of the tip be sure that the resultant surface is shaped to be reasonably perpendicular to the screwdriver shaft.
• When viewing the very end of the tip be sure that it is as close to a perfect rectangle as possible. A trapezoid shape here would be a bad thing. The two large faces of the blade must be parallel with each other and the two edges of the blade also must be parallel to each other. Each of these sets of surfaces should be square to the other.
• The four tapered sides of the blade are not designed to be shaped to any specific angle. Their pitch can be increased or decreased as necessary to achieve the tip width and thickness needed to fit the screw. Also, the actual length of the blade is not important. Again, the key is to get the blade to exactly fit the slot in the screw head.
Besides forming a tip to be square and the proper size the grinding technique also is important. Using a grinder is faster and easier than hand filing, but can be problematic. Better quality screwdriver tips are tempered for hardness and that temper can be lost during the sharpening process if care isn’t taken. Temper is what gives a tool its hardness. If the temper is lost the metal becomes soft. In many cases this can render a tool useless. Grinding can overheat the metal and that can ruin the temper. The solution is to grind just a little at a time – only for a few seconds at a time – and then dip the tip in light machine oil. Water can be used but oil is better. Oil cools slower than water and when you temper you don’t want to cool the metal too quickly. If the tip gets so hot that it discolors (dark blue) the temper is probably lost. Go slow and easy and you won’t have a problem.