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It is not only safe to tighten any type of fastener to specified torque but is the right thing to do. In fact, safety and installation inspectors measure the torque on fasteners to ensure they are installed correctly and to the proper torque.
It is quite easy to apply and measure torque on nuts and bolts because you only need a torque wrench and the right size of a socket. With screws, it is a different ball game unless a screw head has an external hex shape to let you use a wrench or spanner.
Most screws have a round head on the outside and a drive slot in the center where you insert the screwdriver tip. There are more than a dozen types screw drives that I know of including but not limited to slotted/flat-head, Phillips, torx, internal hex, and positive. Accordingly, there are just as many types of screwdrivers as the shapes of screw drive slots.
When you want to tighten these types of screws to a specific torque, you must use a torque screwdriver or an ordinary screwdriver with a hex-shaped handle.
In this post, I show you how to use a torque wrench on an ordinary screwdriver to torque screws to spec.
How to torque screws without over tightening and under tightening
You can use either a hand screwdriver or power tools such as a drill or impact driver to install or remove screws. However, these tools will not tighten a fastener to spec. You need a torque wrench to apply just the right amount of torque.
As I have mentioned, torquing a screw to specification with a torque wrench is not a straightforward job. You not only need a torque wrench and socket, but also a screwdriver with a proper handle.
When I say a screwdriver with a proper handle, I mean a screwdriver handle that is designed for use with wrenches or sockets. Otherwise, it may not be possible to use a torque wrench on just any type of screwdriver to tighten screws to spec or to measure the torque on screws.
Screwdrivers that are designed to be used with wrenches have grooved or ridged plastic or metallic handles. These types of handles allow a wrench or socket to slide over so that you can apply more axial pressure for tightening or loosening screws.
More importantly, these ridged screwdriver handles also allow you to use a regular torque wrench on the screwdriver to tighten screw fasteners to the specified torque. This is the little know secret on why some screwdrivers have ridged plastic handles. Now you know 🙂
What else do you need to know?
Before using a torque wrench, box-end wrench, or ring spanner on a screwdriver, you need to know the following:
1. Size of the screwdriver handle
Screwdriver manufacturers do not label the size of the grooved handles. So, trial and error is the easiest way to determine the size of the wrench that would fit. If you have a wrench set, spanner set, or socket set, you can try each size until you find the one that fits snugly. Once you establish the right size, label the handle to make it easier to pick the right one next time.
2. Type of screwdriver handle
Not all screwdriver handles are shaped for use with wrenches. Only the grooved handles allow a spanner to slide over. Mostly, those ridged handles are made of hard plastic. This makes them withstand stress to prevent rounding off.
3. Torque specification
Some screws such as wood screws and machine screws have very fragile heads. They can easily be stripped by too much torque. Since a wrench on a screwdriver allows you to apply additional axial pressure to a screw, it is important to know how much torque you need in order to avoid stripping the screw head.
Sometimes you might even damage the tip of your screwdriver when you apply too much torque. Different screwdrivers are designed to handle different amounts of torque. So you need to be very careful when using a wrench as leverage for your hand screwdriver.
In a nutshell, when selecting a screwdriver, do not just look at the shape of the tip. It is also important to look at the shape of the screwdriver handle. If you need to tighten screws to a specified torque value, you need a screwdriver with a grooved handle. Such screwdrivers do not provide the most comfortable grip, but on the other hand, they let you slide over a box-end wrench or socket.