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Difficulty: MediumBolts, Nuts, and Washers

An automotive technician installing an alternator mounting bracket consults the service manual, which specifies an M10×1.5×40\text{M}10 \times 1.5 \times 40 hex cap screw. What does the value 1.51.5 represent in this standard metric fastener callout?

  1. A
    The total number of threads per inch along the bolt shank
  2. The distance in millimeters between adjacent thread crestsAnswer
  3. C
    The tensile strength property class rating stamped on the fastener
  4. D
    The nominal diameter of the unthreaded shank in centimeters

Answer

The value 1.5 represents the thread pitch, defined as the distance in millimeters between adjacent thread crests.
In standard metric fastener notation (M10 x 1.5 x 40), the letter 'M' indicates metric ISO thread profile, the first number (10) represents the nominal major diameter in millimeters, the second number (1.5) represents the thread pitch in millimeters between adjacent crests, and the final number (40) is the length of the bolt in millimeters.

Step-by-Step Solution

1
Deconstruct the metric fastener callout notation M10 x 1.5 x 40 into its standard components.
'M' indicates metric ISO thread; '10' is nominal major diameter in millimeters; '1.5' is thread pitch; '40' is fastener shank length in millimeters.
Metric fastener specifications follow the standard format: Metric Designation + Major Diameter (mm) x Thread Pitch (mm) x Length (mm).
2
Determine the physical definition of thread pitch in metric fastener standards.
A thread pitch of 1.5 specifies that there is a 1.5 mm linear distance from the peak of one thread to the peak of the adjacent thread.
Unlike Imperial threads that count threads per inch (TPI), metric fasteners directly measure the axial distance between individual crests.

Key Concept

Metric fastener callout structure and thread pitch specification
Estimated Time:1m 0s
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Topics

Bolts, Nuts, and Washers

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