Nominal Diameter Of Screw Given Unit Bearing Pressure Calculator

Formula Used:

\[ d = \sqrt{\frac{4 \times W_a}{S_b \times \pi \times z} + (d_c)^2} \]

Axial Load On Screw (W_a):

Unit Bearing Pressure For Nut (S_b):

Number Of Engaged Threads (z):

Core Diameter Of Screw (d_c):

Nominal Diameter Of Screw (d):

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1. What is the Nominal Diameter of Screw?

The nominal diameter of a screw is defined as the diameter of the cylinder touching the external threads of the screw. It represents the major diameter of the screw thread and is a critical parameter in mechanical design and engineering applications.

2. How Does the Calculator Work?

The calculator uses the following formula:

\[ d = \sqrt{\frac{4 \times W_a}{S_b \times \pi \times z} + (d_c)^2} \]

Where:

\( d \) — Nominal diameter of screw (m)
\( W_a \) — Axial load on screw (N)
\( S_b \) — Unit bearing pressure for nut (Pa)
\( z \) — Number of engaged threads
\( d_c \) — Core diameter of screw (m)
\( \pi \) — Mathematical constant pi (≈3.1416)

Explanation: This formula calculates the nominal diameter by considering the axial load, bearing pressure, number of engaged threads, and core diameter of the screw.

3. Importance of Nominal Diameter Calculation

Details: Accurate calculation of nominal diameter is crucial for proper screw design, ensuring adequate strength, load distribution, and compatibility with mating components in mechanical assemblies.

4. Using the Calculator

Tips: Enter axial load in newtons (N), unit bearing pressure in pascals (Pa), number of engaged threads (integer value), and core diameter in meters (m). All values must be positive and non-zero.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between nominal diameter and core diameter?
A: Nominal diameter is the major diameter of the screw thread, while core diameter is the smallest diameter of the thread (minor diameter).

Q2: Why is unit bearing pressure important in screw design?
A: Unit bearing pressure determines the contact stress between screw and nut threads, affecting wear resistance and service life of the assembly.

Q3: How does the number of engaged threads affect the calculation?
A: More engaged threads distribute the load over a larger area, reducing the required nominal diameter for a given load.

Q4: What are typical unit bearing pressure values for different materials?
A: Unit bearing pressure varies by material combination - steel on bronze typically ranges from 10-25 MPa, while steel on steel may range from 15-40 MPa.

Q5: Can this formula be used for both metric and imperial screw threads?
A: Yes, the formula is dimensionally consistent and can be used with any unit system as long as all inputs use consistent units.