Box Wrench Versus Open End Wrench

No respectable toolbox is complete without a collection of both box and open end wrenches. Although they are used for the same basic purpose of tightening and loosening nuts, there are situations where one type of wrench works better than the other.

Box Wrench

A box wrench, also known as a box-end wrench, has an enclosed head that grips all faces of the bolt or nut. This feature provides more leverage and less likelihood of slippage compared to an open-end wrench.

Box wrenches are available with 6-point or 12-point heads for use with nuts or bolt heads with a hexagonal shape. There are also 8-point wrenches for square-shaped nuts and bolt heads.

Open End Wrench

An open end wrench has a U-shaped opening that grips two opposite faces of the bolt or nut. The wrench is often double-ended with a different size opening at each end. The ends typically vary by one size increment, e.g., 1/2" and 9/16".

The ends of an open-end wrench are usually angled about 15 degrees to the axis of the handle. This allows the tool to be flipped over, providing a greater range of movement in tight spaces.

Design Features

Some box wrenches are offset to provide knuckle room and clearance around protrusions and other obstructions. The typical open-end wrench is not offset.

The better quality wrenches, whether box or open-end, are made from drop-forged chromium-vanadium alloy tool steels that are chrome-plated to resist corrosion and simplify cleaning.

Combination wrenches combine a box and an open end on opposite sides of the wrench. Both ends are usually the same size. Such wrenches are very useful because they provide the advantages of both types of wrenches.

Reaching the Fastener

One advantage of an open-end wrench relative to a box wrench is that it allows sliding the wrench into position from the side of the nut or bolt. This is very helpful in situations where there is insufficient room to slide the wrench in from the top. A 12-point box wrench is advantageous in situations where swing is limited, especially compared to an open-end wrench.

Fastener Damage

Because open-end wrenches only grip the fitting on two sides, there is a greater likelihood of rounding the fitting if the wrench slips. To minimize the chances of this occurrence, use a wrench that fits exactly and make sure it fully engages the fitting. It is almost impossible to round a nut with a box wrench unless the wrench is too large.