Home
Back
Pitch Diameter Formula:
| From: | To: |
Pitch diameter is the diameter of an imaginary cylinder that passes through the threads where the width of the thread and the width of the groove are equal. It is a critical measurement in thread design and manufacturing.
The calculator uses the pitch diameter formula:
Where:
Explanation: The formula calculates the pitch diameter by subtracting twice the thread height from the outer diameter. The constant 0.6495 represents the standard thread height factor for unified threads.
Details: Accurate pitch diameter calculation is essential for proper thread fit, strength analysis, and manufacturing precision in mechanical engineering and machining applications.
Tips: Enter outer diameter in inches and threads per inch. Both values must be positive numbers greater than zero for accurate calculation.
Q1: What types of threads does this formula apply to?
A: This formula is primarily used for unified thread forms (UNC, UNF, UNEF) which are common in North America.
Q2: Why is the constant 0.6495 used in the formula?
A: This constant represents the thread height factor for unified threads where H = 0.866025P, and the single thread height is 0.6495P (where P = 1/TPI).
Q3: How does pitch diameter affect thread fit?
A: Pitch diameter determines the tightness of fit between mating threads. Proper pitch diameter ensures the correct balance between ease of assembly and thread strength.
Q4: Are there different formulas for metric threads?
A: Yes, metric threads use a different formula: PD = D - 0.6495 × P, where D is the major diameter and P is the pitch in millimeters.
Q5: How precise should pitch diameter measurements be?
A: For most engineering applications, pitch diameter should be measured to within ±0.0005 inches for precision threads, though tolerances vary based on thread class.