Length of the shaft is irrelevant. Please note that a longer shaft on a screw driver does give you more torque if you are opening a can of paint. The problem set up is wrong, or as a physics professor of mine was fond of saying, your conception is wrong. A perfect illustration of the concept is using a flex tip breaker bar and a socket to loosen a bolt. With the bolt screw , socket screwdriver tip and breaker bar screwdriver shaft all aligned straight up and down, the force applied is your arm strength alone, some base level X.
When you flex the breaker bar fully perpindicular to the screw forming a perfect 90 degree angle, you have the most force you can apply to the bolt. Therefore, the longer screwdriver is capable of giving the flesh a mechanical advantage. I wanted to add two things. First, the above is of course a simplification to illustrate the force on the screw, not the screwdriver. After all, of course the screwdriver is being turned.
Second, I have seen spoon tipped screwdrivers and drivers with the flat ground at other than 90 degrees purposefully to engage a slot at an offset.
Torque is the force applied times the distance from the axis you are rotating about. So the torque of the screwdriver only really depends on the thickness of the handle. Longer screwdrivers tend to have larger diameter handles not always and hence the application of more torque. There is supposed to be a relation between the length of a screwdriver and the force you can produce at the business end — a product of the torsion not torque developed in the driver shaft.
Or is this advertising hype? Mallettowardnone, rusty and Patrick have it correct, torque is the product of the force applied to a lever arm of a certain length, perpendicular to the axis of rotation of the object the force is applied to, in this case a screw. Perpendicular is the key word. Yucky technical stuff alert: Physicists and engineers define Torque as Force x Lever arm length x Sine of angle between lever arm and axis of rotation.
The definition allows for non-perpendicular angles. A larger diameter handle will create a longer lever arm. Longer screw drivers often have larger handles, so you can get more torque that way. First of all, if the screwdriver blade fits tightly in the slot of the screw head, the moment about the blade is the integral of all the moments from the center to the edges of the blade. If the fit is not tight, torque is transmitted only at the edges of the blade, so the moment is merely that applied at the edges, and the radius is half the width of the blade.
The overall actual mechanical advantage, however, can depend on the dimensions of what you are turning with the screwdriver. The increased efficiency of the longer 2 foot length of driver is apparent when you are trying to remove really recalcitrant large gauge screws such as in old door hinges and the increased efficiency is undoubtedly because you are able to use your shoulder and elbow to exert greater torque than you could with a shorter driver.
I just tried and can get exactly the same position and leverage, relative to a flat surface, with both. The footlong was much easier to handle as well. I think the screwdrivers that have square shanks are better than the round shank ones. Makes it easy to add a wrench for some awesome torque, regardless of screwdriver length. Why is a long screwdriver more efficient than a short one?
Factual Questions. Every craftsman knows this to be true, but the question is, why is it so? Link to comment Share on other sites More sharing options The Z Machine Posted August 2, The Man from Laramie Posted August 2, Voice Of Reason Posted August 2, Longer screwdrivers tend to have larger handles. EYLive Posted August 2, BroadwayG Posted August 2, I think the only screwdrivers both of you should be handling are ones made with vodka.
In the context of the question YOU win. But what if the larger screwdriver allows you to apply more force? Jaysus Posted August 2, RudiStein Posted August 2,
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