A torque screwdriver is a screwdriver that has a torque limiting clutch that disengages once the desired torque has been reached. Torque is another way of saying “the amount of force applied”. The reason that you would use a torque screwdriver is prevent over-tightening, which can damage the product or affect the screw threads, therefore affecting the quality of the assembly being built. This is very common in manufacturing and production environments, where a specific torque is determined best by the engineer who designed the product or assembly.
The torque measure by these torque screwdrivers can vary from 6 inches/ounce to 190 inches/pound. There is no screwdriver that can measure this entire range, so you will need to determine the torque range you need before buying a torque screwdriver. You may need to buy more than one, or a torque screwdriver set to cover the range of torque you need to measure.
There are several companies that make torque screwdrivers including Neiko, Craftsman, Wiha, CDI Torque, Klein Tools, Wheeler, and many more.
Torque Screwdriver Set
Most fixed torque screwdrivers are sold in sets. The set will include various screwdriver shafts that vary in the tip (Phillips, torx, straight, etc.) as well as the heart of the kit-the adjustable torque handle. “Break” is a term commonly used to describe the point at which the screwdriver reaches its set torque because the clutch mechanism will suddenly release, causing the feeling that the user broke the screwdriver. Since there is such a huge variance in the torque that can be measured by a torque screwdriver, one handle will not measure the entire range, and the bits will vary based on the torque range they are designed to be used for. It would take several sets to cover the entire range available. The clutch mechanism is built into the handle, and is usually adjustable. If you have your own bits, or wish to purchase your own separately, you can just purchase an adjustable torque screwdriver, and create your own set.
Adjustable Torque Screwdriver
The adjustable torque screwdriver is at the center of every set. There are several different designs available. For example, there is the typical straight handle and there is a straight handle with one side that opens up to 90 degrees from the shaft, allowing you to apply more torque than you can with just a straight handle. There are also handles with a bend or angle built in to allow for easier application of greater torque. For the quickest, easiest assembly with adjustable torque accuracy, you are going to want to get an electric torque screwdriver.
Electric Torque Screwdriver
Electric torque screwdrivers can vary in size, shape, and torque range, just as manual ones do. There are models with clutches, and there are also clutchless models that require an external control module, but have no clutch. The models with a clutch work just like a manual screwdriver in that the clutch breaks at the set torque. The clutchless models, however, simply shut off the power when the proper torque is reached. The advantage of a model with a clutch is that there is no external box that needs to be set, but just a dial or lever that needs to be put at the desired torque. These models are self-contained and easier to transport. The advantage of a clutchless model, however, is the dramatically increased accuracy as well as the increased range of torque they can cover.
Torque Wrench Screwdriver
A torque wrench screwdriver is very similar to a torque screwdriver. It measures torque, and has a manual clutch. The only real difference is that instead of a ¼” female end for attaching screwdriver bits, it has a ¼” male end that allows for the attachment of ¼” driver sockets and has an adaptor if you would like to attach screwdriver bits. The operation is otherwise the same.
Amazon.com Products
The first torque screwdriver on Amazon.com is a model produced by Neiko. This screwdriver includes a complete array of bits. The torque varies from 10-50 inch/lbs. It will also fit any other ¼” bits. It features an extra-long shafts, and soft grip handle. It carries a 1 year warranty, and sells for $56.95 on Amazon.com. This screwdriver has a 4 star rating on Amazon.com. The people who review it have said that it is a great inexpensive screwdriver for occasional, around the house use. They all thought it was good for light use, but were afraid it may not stand up to daily, long-term use. If you are looking for an inexpensive model for light use, this would be a good selection.
The next screwdriver is made by Wiha, which is one of the top names in these products. It measures 10-50 inch/lbs. This model has an integrated window that displays the torque to ensure accurate measurements. The torque setting is adjusted with a tool rather than a dial to protect against accidental changes in the torque setting. There is an audible click when the torque setting is reached. This is a very high quality, precision tool. The people who have bought this screwdriver through Amazon.com have called this the “BMW of torque screwdrivers”. The actual accuracy has tested at 1.2%, rather than the advertised 3% in one case. Every review is positive, and most of the people who purchased this have openly professed that they recommend this screwdriver for someone seeking the best quality for daily, long-term use.. This screwdriver sells for $75.98 on Amazon.com.
The next screwdriver is also a Wiha, so I will skip down to the next brand for another comparison. The next brand is a CDI-Torque. It is actually a Torque Wrench Screwdriver. It is adjustable from 3-15 inch/lbs. This screwdriver is designed specifically for the electronics industry and instrument assembly. The torque is adjusted simply with a unique adjusting knob. To adjust the torque, you must pull the knob out before turning it. This helps to prevent accidental adjustment of the torque. There are no customer reviews on this product.
Summary
Torque screwdrivers are used when specific accuracy of screw torque is necessary to prevent damage to the product being assembled. This is most common in industrial environments, particularly music instruments and electrical applications. If such accuracy is required, the manufacturers will be sure to note the requirements in the assembly instructions. There is a wide variety of screwdrivers available, as well as bits to be used. There is such a wide range of torque adjustments that one screwdriver cannot cover the entire range. There are several models available, depending on your specific application. Be sure to know what torque range you need before you make a purchase.