Best Impact Wrenches For Head Bolts: Top Picks Reviewed

Impact wrenches are powerful tools that can be used to tighten or loosen hex-head bolts, nuts, and lag screws. They are particularly useful for automotive work and heavy-duty tasks such as removing lug nuts or large, rusted bolts. When choosing an impact wrench, it is important to consider factors such as power, torque, speed, control, battery life, size, weight, build quality, ergonomics, noise level, warranty, customer support, and price. While impact wrenches are effective for removing head bolts, some people prefer to use a breaker bar to avoid the risk of breaking the bolt heads. Others recommend using a propane/MAPP gas torch to heat the bolt before removal, especially in the case of tight bolts. Additionally, it is generally recommended to avoid using an impact wrench when installing head bolts.

Impact wrenches vs. impact drivers

When it comes to impact wrenches and impact drivers, there are several differences to note, and each has its own advantages and disadvantages.

Drive Styles

Impact drivers use a 1/4-inch hex collet that accepts 1/4-inch hex shank bits. Impact wrenches, on the other hand, typically use a square drive that you attach a socket to. There are also 7/16-inch hex impact wrenches used by utility workers. While impact drivers come in a limited range of styles, impact wrenches cover a much broader range of performance levels and have more specialty versions.

Power Sources

Corded impact drivers do exist, but most construction sites now use cordless models, with 12V and 18V/20V Max being the most common voltages. Similarly, impact wrenches also come in corded and cordless versions. However, the classic impact wrench sound that you might associate with a mechanic's shop or race track is powered by air (pneumatic). Most tradespeople use cordless models, while mechanics tend to rely on pneumatic impact wrenches.

Torque

In general, impact wrenches offer more power (torque) than impact drivers. However, some high-powered impact drivers in the 18V/20V max class, especially on 12V platforms, can rival the torque of compact impact wrenches. Impact wrenches start around 100 ft-lbs (1200 in-lbs) and can produce well over 1000 ft-lbs (12,000 in-lbs) of torque. Impact drivers, on the other hand, typically produce up to 2000 in-lbs of torque (167 ft-lbs).

Speed

Impact drivers tend to have higher maximum speeds, often reaching 3600 RPM or more, while cordless impact wrenches usually max out under 2000 RPM. Pneumatic (air) impact wrenches are the exception, with some models capable of reaching 8000 RPM.

Size

Impact drivers are typically more compact and lightweight than cordless impact wrenches. With impact wrenches, the size and weight of the tool usually increase with its power level. Pneumatic impact wrenches are an exception, as they don't have a motor, so they can sometimes be lighter than impact drivers.

Use Cases

Impact drivers are screwdriving specialists, suitable for working with fasteners that require a driver bit, such as slotted, Phillips, square, or Torx. They are also capable of drilling with compatible shank bits. Impact wrenches, on the other hand, are ideal for working with hex head fasteners like nuts and bolts or timber screws, where you use a socket to grab around the fastener.

Price

Impact drivers are generally more affordable, with budget models starting at $100 and premium models costing around $250. Impact wrenches are more expensive, with prices ranging from $250 to $500 or more.

In summary, both tools have their unique uses, and the right choice depends on the specific tasks you need to perform. Impact drivers are versatile and suitable for a wide range of DIY projects, renovations, and simple carpentry. Impact wrenches, with their higher torque, are better suited for heavy-duty applications like removing and installing heavy-duty bolts and nuts.

Cordless, corded, or air-powered wrenches

When it comes to choosing the right impact wrench for head bolts, you have three main options: cordless, corded, or air-powered tools. Each type has its advantages and considerations, so let's explore them in detail to help you make an informed decision.

Cordless Impact Wrenches:

Cordless impact wrenches offer unmatched mobility and convenience. With advancements in battery technology, these tools have become viable alternatives to their pneumatic counterparts. You can easily take them wherever you need to work without being tethered to a compressor with an air hose. They are ideal for both heavy-duty and compact applications. The higher-end cordless impact wrenches produce greater torque, with outputs ranging from 225 foot-pounds for sub-compact models to an impressive 1,500 foot-pounds for the most powerful options.

Cordless impact wrenches provide multiple speed and torque settings, allowing you to adjust the power according to the task at hand. They are extremely comfortable to use, as the concussive blows are smoothly transferred to the fastener, reducing the reactionary torque felt in your hand, wrist, or arm. Additionally, they offer excellent control to prevent over-tightening of fasteners or spinning off lug nuts.

Corded Impact Wrenches:

Corded impact wrenches, also known as electrical impact wrenches, provide consistent power without the need to worry about battery recharging. They are a good choice if your workspace has limited access to outlets and you want uninterrupted power delivery. These tools are available in various sizes, with the 1/2-inch impact wrench being the most common and suitable for most applications.

Air-Powered Impact Wrenches:

Air-powered impact wrenches, also known as pneumatic impact wrenches, were traditionally the go-to choice for professional mechanics. They deliver high torque output and are often more affordable than their cordless counterparts. However, they require a significant investment in an air compressor that can output close to 100 psi to run effectively. Air-powered impact wrenches tend to have higher torque capabilities, but they are less portable and require a compressed-air setup.

In summary, the decision between cordless, corded, or air-powered impact wrenches depends on your specific needs. Cordless models offer unmatched mobility, corded models provide consistent power, and air-powered models deliver high torque at a lower cost but with reduced portability. Consider the nature of your work, the accessibility of power sources, and your budget when making your choice.

Torque requirements

Torque is a measure of an impact wrench's ability to drive in lag bolts or loosen nuts, and it is the most important representation of power for an impact wrench. Most cordless impact wrenches can produce torque outputs of over 250 foot-pounds, which is more than enough power to drive in the fattest lags and loosen rusty, corroded nuts.

The torque output of an impact wrench depends on the model. Sub-compact models can produce 225 foot-pounds of torque, while the most powerful impact wrenches can produce 1,500 foot-pounds of torque. The higher-end and pricier cordless impact wrenches generally produce the greatest amount of torque.

The torque output of an impact wrench is also affected by the bolt size. Smaller fasteners have smaller amounts of metal, so they can handle less torque before breaking or stripping out. A torque wrench will have a maximum torque it can produce, and the user must set the torque for the specific bolt size. For example, a torque of 1100 ft/lbs on a 5/8-inch bolt may snap a 1/2-inch bolt, so the user must refer to the recommended torque for the specific bolt size.

The type of bolt head also affects the torque output of an impact wrench. A socket head cap screw (Allen key) will have a different torque spec than the same size bolt with a full-size hex head. The wider the torquing area, as in a full-sized hex head, the greater the potential for torque.

In addition to bolt size and type, thread pitch also plays a role in determining the torque output of an impact wrench. A finer thread pitch will result in higher clamping force for a given torque.

Risk of over-tightening

When using an impact wrench, there is a risk of over-tightening due to the tool's high torque output. This can lead to damage to the fastener or the material it is being tightened against. To avoid over-tightening, it is recommended to use the lowest setting on the impact wrench and finish with a torque wrench. This will give you a better ''feel'' for how the tool is working and help you judge the appropriate torque setting.

Additionally, some impact wrenches have modes that automatically slow down the wrench after a bolt has been broken loose, preventing over-tightening and spin-off. These modes can be very useful when working with similar fasteners, such as lug nuts, as they allow you to get a consistent torque value for each fastener.

Dial-down adjustment settings when tightening fasteners, and always refer to the manufacturer's recommendations for torque values. If you are working on a vehicle, for example, a Haynes manual or shop manual can provide you with the recommended torque values for various fasteners.

It is also important to note that impact wrenches should not be used on certain types of fasteners, such as spark plugs and head bolts, as they can easily damage soft metals and thin threads. For these types of fasteners, it is recommended to use a torque wrench or hand tools to tighten them appropriately.

By following these guidelines and using the appropriate tools, you can effectively avoid the risk of over-tightening when using an impact wrench for head bolts.

Size and weight

When choosing an impact wrench for head bolts, size and weight are important factors to consider. The size and weight of the impact wrench will impact its ease of use, manoeuvrability, and user comfort during operation.

Impact wrenches come in different sizes, including 1/4-inch, 3/8-inch, and 1/2-inch variants. The 1/4-inch impact wrench is ideal for small, delicate tasks, while the 3/8-inch wrench is a versatile "do-it-most" tool. The 1/2-inch impact wrench, however, is designed for heavy-duty applications involving large nuts and bolts. When selecting an impact wrench, it is crucial to consider the size of the bolts or nuts you will be working with to ensure the wrench can effectively engage and apply the necessary torque.

In addition to the drive size, impact wrenches also vary in terms of tool body size. They are typically available in full-size, compact, and sub-compact options. Full-size impact wrenches have larger and longer tool heads, allowing for higher torque specifications. They are well-suited for removing stubborn, rusted nuts and bolts but may not fit into tight spaces. On the other hand, compact and sub-compact impact wrenches feature shorter and less bulky tool heads, making them more manoeuvrable in confined areas. While they have lower torque specifications than their larger counterparts, they provide sufficient torque for most assembly and disassembly tasks encountered by the average user.

The weight of an impact wrench is another important consideration. Heavier impact wrenches tend to have beefier components and can deliver higher torque. However, they can be more challenging to handle, especially during extended use, as they can cause fatigue in the user's wrists, arms, or forearms. Lighter impact wrenches, on the other hand, are easier to manoeuvre and reduce user fatigue, making them more comfortable for prolonged use.

When selecting an impact wrench, it is essential to strike a balance between size and weight to ensure optimal performance and user comfort. A compact and lightweight impact wrench may be more suitable for working in tight spaces or overhead applications, while a heavier and more powerful wrench may be preferred for heavy-duty tasks involving large bolts or nuts. Ultimately, the decision should be based on the specific requirements of the task at hand.

Frequently asked questions