crow's-foot spanner A wrench that is used for gripping the nuts on the ends of tubes. It is similar to a box-end wrench but, instead of encircling the nut completely, it has a narrow opening just wide enough to allow the wrench to fit over the tube, and thick jaws to increase the contact area with the nut. This allows for maximum contact on plumbing nuts, which are typically softer metals and therefore more prone to damage from open-ended wrenches. common
Compressed air is the most common power source for impact wrenches, providing a low-cost design with the best power-to-weight ratio. A simple vane motor is almost always used, usually with four to seven vanes, and various lubrication systems, the most common of which uses oiled air, while others may include special oil passages routed to the parts that need it and a separate, sealed oil system for the hammer assembly. Most impact wrenches drive the hammer directly from the motor, giving it fast action when the fastener requires only low torque. Other designs use a gear reduction system before the hammer mechanism, most often a single-stage planetary gearset usually with a heavier hammer, delivering a more constant speed and higher "spin" torque. Electric impact wrenches are available, either mains powered, or for automotive use, 12-volt, 18-volt or 24-volt DC-powered. Recently, cordless electric impact wrenches have become common, although typically their power outputs are significantly lower than corded electric or air-powered equivalents. Some industrial tools are hydraulically powered, using high-speed hydraulic motors, and are used in some heavy equipment repair shops, large construction sites, and other areas where a suitable hydraulic supply is available. Hydraulic impact wrenches have the advantage of high power-to-weight ratio.
Cordless impact wrenches come in two body styles: inline and pistol-grip. The inline style of impact wrench looks a lot like a large screwdriver, with a grip behind the hammer and anvil. The pistol style is shaped like a handgun, and the grip rests underneath the motor. Cordless impact wrenches also feature a selection of socket sizes designed to fit nuts and bolts of different sizes. The following table shows what socket sizes work with each impact wrench shape. Inline wrenches work best for jobs where you’re working in tight spaces and simply can’t fit a pistol-type impact wrench. If you plan to work on machinery, especially cars, then an inline impact wrench is a must-have tool.

Wrenches and applications using wrenches or devices that needed wrenches, such as pipe clamps and suits of armor, have been noted by historians as far back as the 15th century.[2] Adjustable coach wrenches for the odd-sized nuts of wagon wheels were manufactured in England and exported to North America in the late eighteenth and early nineteenth centuries. The mid 19th century began to see patented wrenches which used a screw for narrowing and widening the jaws, including patented monkey wrenches.

Many users choose to equip their air-powered impact wrenches with a short length of air hose rather than attaching an air fitting directly to the tool. Such a hose greatly aids in fitting the wrench into tight areas, by not having the complete coupler assembly sticking out the back of the tool, as well as making it easier for the user to position the tool. An additional benefit is greatly reduced wear on the coupler, by isolating it from the vibration of the tool. A short length of hose also prevents the air fitting from being broken off in the base of the tool if the user loses their grip and the tool is allowed to spin.

The DEWALT 20-Volt Max Lithium-Ion 1/2 in. High The DEWALT 20-Volt Max Lithium-Ion 1/2 in. High Torque Impact Wrench with Detent Pin (Tool-Only) is designed for mechanical contractors plumbers automotive mechanics maintenance and repair professionals and remodelers who demand a tool for difficult fastening applications such as driving and removing fasteners or nuts and bolts in wood metal ...  More + Product Details Close
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