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Question

Difficulty: MediumStandard Measurement and Layout Tools

A machinist needs to locate and scribe the exact center point on the end of a round steel bar before drilling. Which component of a combination square set is specifically designed to straddle cylindrical stock and bisect its circular cross-section?

  1. A
    Protractor head
  2. Center headAnswer
  3. C
    Square head
  4. D
    Trammel head

Answer

Center head
The center head attachment fits onto a standard steel rule and has two symmetrical arms forming a V-notch. When placed against a cylindrical workpiece, the edge of the attached blade automatically bisects the circular cross-section. Scribing two lines at different angles produces an intersection at the exact center of the round bar.

Step-by-Step Solution

1
Identify the workpiece geometry and the required layout task.
The workpiece is a round cylinder, and the objective is finding the center point on its end face.
Choosing the correct layout tool depends directly on the geometry of the workpiece.
2
Analyze the specialized attachments available in a standard combination square set.
A combination set includes a square head (for 90-degree and 45-degree flat layouts), a protractor head (for variable angles), and a center head (with a V-shaped notch).
The center head has two arms forming an angle that positions the attached rule exactly along the diameter of any round stock placed inside it.
3
Determine the layout procedure with the center head.
Scribing a line along the rule, rotating the head roughly 90 degrees, and scribing a second line creates an intersection at the exact geometric center.
Two intersecting diameters pinpoint the true center of a circle.

Key Concept

Identifying combination square attachments and their specific layout functions
Estimated Time:45s
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Topics

Standard Measurement and Layout Tools

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