Talking Power Tool Torque - a longer discussion
Updated: Mar 1, 2019
First of all, what is power tool torque?
The answer is: it's the twisting force a power tool can exert on something it is driving. To put it another way: it's how tightly the power tool will drive a screw or a nut or bolt, or how large a drill bit it will turn to make a hole, or how hard it will try to turn a drill bit before it gets stuck!
An impact screwdriver and an impact wrench depend on producing high torque to drive screws, nuts and bolts, but they don't necessarily need to produce all that much power.
Torque is not power. Torque is not an indicator of how powerful your power tool is. Torque and power are often confused. It is a misconception to say that they are the same; they are most definitely not. Torque is only about how forcefully your power tool can work. Power is about how fast as well as how forcefully your power tool can work. You often need both ratings to try to make a judgement about which power tool is best for you. For further discussions on power tool power please see KwikPro blogs Cordless Tool Power, and Corded Tool Power.
A good way to consider how power tool torque works is to take a look at a two-gear rotary drill head when attached to a KwikPro motor handle. The power – mechanical twisting force and speed - comes from the motor in the KwikPro motor handle and at full throttle is the same whichever gear you select. Nothing changes at the motor end whichever gear you use. Think about it like this, the motor hasn't changed, it is still spinning at the same speed and the maximum twisting force, the torque, it can exert at the input end of the drill head hasn't changed either. In gear 1 the chuck rotates at a relatively slow speed and it's difficult to stop it from turning, but it takes a while to get a hole drilled. If you change to gear 2 the force goes down but the speed goes up. In gear 2 drilling the same size hole as in gear 1 starts off being much quicker until the drill bit gets stuck!
What is torque measured in? If you look up the spec for a power tool such as an impact driver you are most likely to see torque quoted in Nm or lb/ft or ft/lb; sometimes for very low torque you may see Ncm or Nmm or lb/in or in/lb and for very high torque you may see kNm or ton/ft or ft/ton.
Power tools come in all shapes and sizes but which produce most torque. As a guide, larger heavier power tools are likely to have higher torque ratings. In order for a power tool to produce higher torque it will usually need either or both a larger motor and or a larger gearbox. Both of these are likely to be heavier than in power tools producing lower torque.
If you have a choice of cordless power tools all with similar size batteries and they seem to be similar in size and weight how do you decide which is for you? How do you compare power tool torque?
One way some Youtubers have tried is to join two power tools together nose to nose to see which one will out turn the other and for how long. This certainly shows which of the two power tools has the most torque but is it useful? It makes an entertaining video but how much use is it to someone looking to choose which power tool to buy?
As discussed above, having more torque is not the whole story and no guarantee that one power tool will work better for you than another.
Instead, try considering what you want from your power tool: what are you going to use it for most of the time? If it’s a drill, are you going to be drilling lots of large holes and only occasional small holes or vice versa? If it’s an impact screwdriver are you mainly going to be driving large screws or small? Will it be important to get the screws in fast or will it be more important to get them in very tight? Similarly, if it’s an impact wrench will you be driving large nuts and bolts or small, and is speed most important or tightness? Also ask yourself if there is any point in having a power tool that can tighten large screws or nuts and bolts to really high torques if you really only want to tighten small screws or nuts and bolts. Buying larger than you need may not be a great idea. An over-size impact driver will easily over-tighten smaller fasteners and fixings which can result in them shearing off, so whilst the torque may be very impressive it might not be much use to you. Also ask yourself if you need to use the power tool one handed. If you do, do you really want a power tool that is uncomfortably heavy, causes fatigue and can wrench your wrist?
With power drills such as the KwikPro combi and rotary drill heads, which have two gears, the choice is easier because you’ll always have the flexibility of one gear for jobs that need higher torque and another gear for jobs that need higher speed. With these power tools look for good construction and decide on your work priorities. If you need to work one handed a heavy power drill that you cannot hold comfortably will be no use to you, irrespective of how much torque it can produce.
When it comes to impact screwdrivers and wrenches the choice is also about how heavy a power tool you are happy to work with. For example, a very high torque impact driver is likely to weigh considerably more than a medium or low torque rated driver. If you need to use your power tools one-handed or need to carry them up ladders or considerable distances before you can use them, they’re weight may be more important than their maximum tightening torque. The KwikPro impact screwdriver head and impact wrench head are both medium torque rated and very easy to carry with the KwikPro motor handle, and when you need to carry them hands-free it's really easy with the unique dedicated KwikBelt toolbelt
And also consider this: will you be using all your power tools all of the time? If not, would an easy to carry power tool system like
the KwikPro Gold or Silver power tool systems work better for you? The KwikPro systems will provide far superior versatility and convenience as well as all the usual attributes of high quality regular power tools.
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