Threads, Fasteners & Springs — For inch threads, pitch (in inches) equals 1 divided by the threads per inch (TPI); therefore, stating pitch = 12 / TPI is incorrect.

Introduction / Context:
Pitch is the axial distance from a point on one thread to the corresponding point on the next thread of the same start. In inch systems, threads per inch (TPI) directly determine pitch by a reciprocal relation.

Given Data / Assumptions:

• Unified (inch) thread specification.
• TPI = number of threads per 1 inch of axial length.
• Pitch is measured along the axis, same start to next.

Concept / Approach:
If a screw has TPI threads over one inch, the spacing between adjacent threads is 1/TPI inches. The statement 12/TPI would imply 12 inches per “thread,” which is dimensionally wrong for pitch.

Step-by-Step Solution:
1) Define pitch: axial distance between adjacent threads (same start).2) Compute pitch = 1 / TPI.3) Compare with 12 / TPI—this yields twelve times the correct value.4) Conclude the given statement is incorrect.

Verification / Alternative check:
Example: 20 TPI → pitch = 1/20 = 0.05 in; using 12/20 would give 0.6 in, clearly wrong.

Why Other Options Are Wrong:
TPI/12 has wrong units; saying pitch is independent of TPI ignores the definition; for multi-start, lead = pitch * starts, but pitch remains 1/TPI for each start.

Common Pitfalls:
Confusing “lead” with “pitch”; mixing inch and foot units.

Final Answer:
Incorrect