The Turn of the Screw, Part One.

How to Operate a Screwdriver.

Almost everyone has used a screwdriver at some point in their life. 

As simple as the tool seems to be, many find it difficult and awkward to use, and many fail to rotate the recalcitrant screw without bloodshed. 

So this article is dedicated to those who approach this simplest of tools with fear and loathing.

Consider the tool itself.  It is far younger than the axe and hammer in Man the Tool Maker’s inventory by several hundred thousand years.

It has but three parts, the handle, the shaft, and the tip, or blade.  There are no moving parts aside from the tool itself.  It is pretty obvious which end to grasp, and the other end will be as far from the grasping hand as the shaft will allow.

Before getting into the intricacies of the handle, let us first discuss how the tool works, the physics involved and some of the engineering considerations for this tool.

There is a blade, a shaft, and the handle.  The blade comes in many shapes and sizes, but for now let us consider the ordinary flat bladed screwdriver.  The wider the blade the more twisting power the screwdriver has because in effect the blade is two levers, each the length of half the diameter of the screw slot which is used to turn the screw.

Therefore if the only screwdriver available is less than the total width of the slot, place it so that one side of the blade is at the end of the slot.  That way the screwdriver will be powering the screw at its maximum torque on the one side.

The best choice is a blade the same width as the slot.  It should fit the slot tightly.  Most blade problems come from the condition of the blade.  If the blade tip is rounded and eroded (the usual condition), file it flat on both sides, and square across the tip so its edges are sharp.

A second problem is the hardness of the blade. Soft steel erodes and the blades wear into blunt instruments suited only for damaging the rims of paint cans. Chromium and vanadium added in tiny quantities makes steel hard and tough. Look for those words on the shaft of the tool, or the name of a famous maker that sells tools with a lifetime warranty. Avoid chrome plated tools, the chrome is too hard to file and often flakes off, it usually hides an inferior grade of steel.

Choosing the correct shaft.  Square shafts are really cool because a wrench can be used on the shaft to help turn the screw if it is really stuck. The longer the shaft, the easier the tool gets to use.

When you twist the screwdriver, your hand keeps making tiny errors of position as it tries to maintain the blade in a vertical position in the slot of the screw.  Short shafts translate these tiny errors into big changes of angle, whereas long shafts make the angle errors smallest.  Use the longest shaft you can for the job.

Handles are also important because through the handle, your hand applies the twist.  The fatter the handle the greater the turning power your hand has, because it is all about that radius as a lever principle again.

 

For comfort, the handle should have a smooth flat end that fits your palm.  From my experience of fifty years, smooth almost cylindrical handles are best. 

The worst handles have serrated rubber grips that become irritants, and domed tops that injure the palm when heavy pressure is applied.

Proper use means pressing down with the handle while twisting the thing at the same time.  If that handle tapers to the shaft, your fingers have less torque, and they tend to slide down.  The flat top allows maximum pressure with comfort, while a long straight cylinder gives best grip for the fingers.  Two handed is easy if the handle is big. 

One hand on the top for position and pressure, the other on the handle for turning.  If you need more grip, put on a pair of rubber kitchen gloves.

Most of the operation of a screwdriver needs little power, so usually I press lightly with the top and use my other hand=s fingers to spin the shaft.  No wrist fatigue, faster spinning. 

Turning it one handed, press lightly at the top, and spin the handle with your fingers until you need to apply more torque and begin using your wrist.

About paint in the slot and other problems like partly worn grooves. 

With your sharp ended screwdriver right at the end of the slot, angle it slightly and tap with a small hammer on the side of the blade to drive the paint from the groove. 

This sliding the blade into the slot from the side gives a good fit and better turning due to the tighter fit in the slot. Badly worn screws can be cut with a hacksaw blade to make a fresh groove to turn with. If you do this do not make much of a cut because you are also weakening the already compromised head.

Another trick once the screwdriver is correctly positioned in the slot is to give a sharp rap on top of the handle. this shocks the screw threads in the holding material and frequently makes the removal easier. 

It is not illegal to use WD40 on a screw overnight if it is very resistant.

It soon becomes obvious that a completely equipped person has a multitude of screwdrivers.  Long shaft, short shaft, medium shaft.  Robertson, Phillips, Torx, Star, Flat blade, and more esoteric designs abound. 

Not to mention broken screw extractors, small hacksaw blades, and so forth.

For those handy types that like to shop for, buy and use tools B this is a good thing.

For the rest? 

Hire a handyman B or marry one. 

For the right woman, I can be had.

Next post?  


All about the screws these things turn. And the slots in them that help or hinder the worker.

Here is a picture of three of my stock of screwdrivers. One is an antique from the 1930's the other two are new with a capacity for quickly changing the tip to match the screw to be rotated. Note that all have fairly long shafts for the size of the tip.