- Effective Thread Length Calculator helps engineers, designers, and machinists determine how much of a bolt’s thread is actually engaged and fully effective in holding a joint. This tool is essential in mechanical design, structural engineering, and manufacturing because the strength of a bolted connection depends on the length of thread that is properly engaged between the fastener and the mating component.
此计算器属于 fastener and mechanical design calculator category. It helps ensure the bolt is used within safe and efficient design limits, especially when working with tapped holes or nuts in machinery and structures.
formula of Effective Thread Length Calculator
地点：
- L_e = Effective Thread Length (units: mm, inches)
- L_engaged = Actual length of thread engagement between the bolt/screw and the mating component
- For bolt and nut: L_engaged = thickness of the nut or portion of the bolt thread inside the nut
- For bolt in a tapped hole: L_engaged = depth of the tapped hole – chamfer or incomplete thread at the start
- L_full_thread = Length of the fastener’s thread that has fully formed threads
- L_full_thread = Total thread length – (length of incomplete threads at start + run-out at end)
笔记:
- Incomplete threads at the start are usually about 1–2 pitches
- Run-out length is about 1–3 pitches, depending on manufacturing method
- Thread standards such as ISO 965 和 ASME B1.1 provide more accurate values based on thread type
The final effective thread length is the shorter value between L_engaged and L_full_thread, because only the overlapping part with complete threads can effectively hold the load.
快速参考通用术语表
| 按揭年数 | 描述 |
|---|---|
| L_e | Effective thread length where full engagement occurs |
| L_engaged | Actual overlap between bolt thread and mating part |
| L_full_thread | Length of fastener with full, usable threads |
| Incomplete thread | Thread portion not fully formed, usually at start or end of bolt |
| 用完 | Tapered end section where threads become incomplete |
| 沥青 | Distance between adjacent threads, used to estimate incomplete sections |
| 螺纹孔 | A hole in a material with internal threads created using a tap |
Example of Effective Thread Length Calculator
Let’s calculate the effective thread length for a bolt used in a tapped hole.
- Bolt thread length = 25 mm
- Incomplete threads at start = 2 pitches = approx. 2.5 mm
- Run-out at end = 2 pitches = approx. 2.5 mm
- L_full_thread = 25 – (2.5 + 2.5) = 20 mm
- Tapped hole depth = 18 mm
- Chamfer/incomplete thread at start = 1.5 mm
- L_engaged = 18 – 1.5 = 16.5 mm
现在应用公式：
L_e = Minimum of (16.5 mm, 20 mm) = 16.5 mm
回答: The effective thread length is 16.5 mm
This means that even though the bolt has 20 mm of usable threads, only 16.5 mm are engaged due to the tapped hole depth.
最常见的常见问题解答
Effective thread length directly impacts the strength of the threaded connection. A shorter length may lead to failure under load, while an overly long bolt may be unnecessary and cost more.
Not always. Only the portion that has complete threads and is fully engaged with the mating part is considered effective. Incomplete threads or thread run-outs do not contribute to load-bearing.
As a rule of thumb, incomplete threads at the start or run-out end are usually 1 to 3 times the pitch of the thread. For precise values, refer to fastener standards like ISO 965 or ASME B1.1.