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Difficulty: EasyWrenches

While servicing an alternator mounting bracket secured by a 13 mm13\text{ mm} hexagonal bolt, a worker needs to select the correct hand tool. Which tool should be selected to turn this fastener safely without slipping or damaging the bolt head?

  1. A
    A 1/2 in1/2\text{ in} box-end wrench
  2. A 13 mm13\text{ mm} combination wrenchAnswer
  3. C
    A 9/16 in9/16\text{ in} open-end wrench
  4. D
    A standard Phillips screwdriver

Answer

A 13 mm13\text{ mm} combination wrench is the proper tool because it provides an exact dimensional match for a 13 mm13\text{ mm} hexagonal fastener.
The correct choice is the 13 mm13\text{ mm} combination wrench. Metric fasteners must always be driven using metric-sized wrenches of the exact nominal dimension to ensure complete contact across the bolt flats and prevent rounding.

Step-by-Step Solution

1
Identify the fastener specification and size
The fastener is a metric hex bolt requiring a 13 mm13\text{ mm} tool opening.
Matching the fastener standard (metric vs. fractional SAE) is essential to avoid tool slippage.
2
Compare candidate tool sizes against the 13 mm13\text{ mm} fastener
A 1/2 in1/2\text{ in} tool equals 12.7 mm12.7\text{ mm} (undersized), a 9/16 in9/16\text{ in} tool equals 14.29 mm14.29\text{ mm} (oversized), and a screwdriver cannot grip external hex flats.
Using an improperly sized or incorrect category of hand tool damages both the fastener and the tool.
3
Select the exact matching metric combination wrench
The 13 mm13\text{ mm} combination wrench securely engages the bolt head.
An exact match distributes mechanical torque evenly across the fastener's load-bearing surfaces.

Key Concept

Metric versus Imperial Fastener Sizing and Proper Wrench Selection
Estimated Time:40s
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Topics

Wrenches

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