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Difficulty: HardGripping and Holding Tools

A technician needs to use tongue-and-groove (water-pump) pliers to loosen a seized cylindrical collar. To maximize gripping force and prevent the tool's joint from slipping out of its adjustment track under heavy torque, how should the pliers be positioned and rotated?

  1. A
    Position the pliers so that the rotational force pushes against the upper jaw, transferring torque directly into the pivot bolt.
  2. Position the pliers so that the rotational force pulls toward the lower jaw, forcing the undercut tongue deeper into the mating groove.Answer
  3. C
    Position the jaws symmetrically across the collar and turn in either direction, as the dual-direction serrations grip equally regardless of rotational orientation.
  4. D
    Position the plier handles perpendicular to the turning axis with the jaw throat facing away from rotation so the joint can freely self-adjust under load.

Answer

Position the pliers so that pulling force is applied toward the lower jaw, which forces the undercut tongue deeper into the mating groove.
Tongue-and-groove pliers are directional gripping tools. When positioned so that the rotational force pulls toward the lower jaw, the torque applied to the handles works with the rotational resistance of the workpiece to seat the tongue deeper into the mating groove channel. This self-energizing clamping effect maximizes grip and prevents the pivot joint from opening or stripping under heavy loads.

Step-by-Step Solution

1
Analyze the mechanical design of tongue-and-groove pliers.
Identify that the tool consists of a fixed upper jaw and an adjustable lower jaw that locks into curved undercut grooves.
Understanding the interlocking mechanism is necessary to determine how applied force interacts with the pivot joint.
2
Determine the direction of applied rotational force relative to the jaws.
When pulling the handles toward the lower (movable) jaw, reaction force from the workpiece pushes the lower jaw inward.
This inward reactive force drives the tongue firmly into the groove channel, locking the adjustment in place and amplifying clamping pressure without straining the pivot bolt.
3
Evaluate the failure mode of reverse operation.
Pulling against the upper jaw forces the lower jaw away from the workpiece, causing the tongue to jump out of the track and rounding the surface.
Correct tool orientation prevents joint damage, workpiece marring, and technician injury.

Key Concept

Directional loading and jaw engagement mechanics in tongue-and-groove pliers
Estimated Time:1m 15s
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Topics

Gripping and Holding Tools

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