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Question

Difficulty: MediumScrewdrivers

An automotive technician observes that a fastener recess is cross-shaped with slightly rounded internal corners and a blunt, flat center. Using a sharp, pointed cross-slot driver causes the tool to slip out under torque. Which screwdriver is designed specifically to engage this blunt-bottomed cross recess?

  1. A
    Frearson screwdriver
  2. Phillips screwdriverAnswer
  3. C
    Robertson screwdriver
  4. D
    Torx screwdriver

Answer

Phillips screwdriver
The Phillips screwdriver is specifically designed with a blunt tip, 30-degree flutes, and rounded internal corners to seat fully inside standard Phillips fasteners without bottoming out prematurely.

Step-by-Step Solution

1
Analyze the fastener head geometry described in the scenario.
The fastener has a cross-recess pattern characterized by a blunt center and rounded internal corners.
Accurate identification of the fastener recess geometry is necessary to select the matching driver profile.
2
Differentiate between standard cross-slot screwdriver designs.
The Phillips design uses a blunt tip and 30-degree flutes, whereas the Frearson design uses a sharp point and 45-degree flutes.
Using a pointed Frearson driver in a Phillips fastener causes the tip to bottom out before the wings fully seat, causing cam-out.

Key Concept

Cross-recess screwdriver tip geometry and proper fastener engagement
Estimated Time:1m 0s
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Topics

Screwdrivers

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