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Thread engagement and pullout estimate calculator

Engineering calculators (Beta)

Compare female-thread pullout, male-thread stripping and bolt tension from effective engagement and separately established allowables.

Inputs

Choose units and enter numbers. Full-width digits and fractions such as 1/8 or 1 3/8 are accepted. Changing a unit converts the entered value.

Results

Reference calculation only. Results do not certify suitability for an actual design or its safety.

Diagram

Inputs: select a blue symbol to edit Results: red-orange values and lines

Formula and applicability

Fd=kF; As≈πdₘLe/3; Fh=Asτh; Fb=Asτb; Ft=Atσa; Lreq=3Fd/[πdₘ min(τh,τb)].

Displayed values are rounded. Diagrams illustrate the calculation conditions. Initial material and fluid properties are examples; replace them with values for the actual material, temperature and conditions.

Reference
Using this information as a reference

Equations assume particular loads, supports and deformation ranges. Check inputs, units and the applicability of each equation. Diagrams explain conditions; they are not manufacturing drawings or proof of safety.

Material values are typical values or reference ranges, not certified product properties or ready-to-use design allowables. They vary with standards, product form, dimensions, temper and temperature. Check the specifications and inspection certificates for the actual product.

Displayed safety factors and checks apply only to the supplied inputs and calculation model. They do not automatically establish the safety of a complete design, including code compliance, service life, fatigue or joints. For actual design, manufacture and use, separately verify applicable regulations and standards, product specifications, and the necessary tests and engineering review.

Calculations do not submit input values to a server. Results are not an automatic code-compliance or safety determination.

この計算で求められること

有効なかみ合い長さと材料ごとの許容せん断応力から、めねじ・おねじの抜けとボルト引張を分けて比較します。

入力・結果・適用条件を確認する

主な入力

  • ねじの有効径 dₘ
  • ピッチ p
  • 完全ねじ部の有効かみ合い長さ Le
  • ねじに作用する最大軸力 F（締付け分を含む）
  • 軸力に掛ける比較倍率 k
  • めねじ側の許容せん断応力 τh（例）
  • おねじ側の許容せん断応力 τb（例）
  • ボルトの引張応力断面積 At
  • ボルトの許容引張応力 σa（例）

得られる結果

  • 比較倍率後の軸力 Fd (N)
  • めねじの概算比較荷重 (N)
  • おねじの概算比較荷重 (N)
  • ボルト引張の比較荷重 (N)
  • 両側の抜けに必要な概算長さ Lreq (mm)
  • ピッチ単位で切り上げた必要長さ (mm)
  • 必要な完全ねじ山数の概算 (—)
  • 3つの比較の最小余裕 (—)

Fd=kF; As≈πdₘLe/3; Fh=Asτh; Fb=Asτb; Ft=Atσa; Lreq=3Fd/[πdₘ min(τh,τb)].

一般的な金属ねじの初期検討用の経験的なせん断面積近似です。1/3はねじの不完全なかみ合いを見込む係数で、特定のJISねじ公差の精密計算ではありません。有効径と完全ねじ長さは実物・規格条件で確認し、面取り・逃げ・不完全ねじを除きます。軸力Fは外力だけでなく締付け分を含む最大ねじ負荷です。許容応力は使用温度・材料・設計基準に合う値を別途決めて入力します。薄肉ボスの割れ、曲げ、疲労、クリープ、インサート、樹脂ねじ、ねじ山ごとの不均等負担は判定しません。

関連する計算

What this calculator does

Compare female-thread pullout, male-thread stripping and bolt tension from effective engagement and separately established allowables.

Inputs, outputs and applicability

Inputs

  • Thread pitch diameter dₘ
  • Thread pitch p
  • Effective engagement Le of complete threads
  • Maximum thread axial force F, including preload
  • Comparison multiplier k on axial force
  • Female-thread allowable shear τh (example)
  • Male-thread allowable shear τb (example)
  • Bolt tensile-stress area At
  • Bolt allowable tensile stress σa (example)

Results

  • Factored axial force Fd (N)
  • Estimated female-thread comparison load (N)
  • Estimated male-thread comparison load (N)
  • Bolt tensile comparison load (N)
  • Estimated engagement Lreq for both thread sides (mm)
  • Required length rounded up to whole pitches (mm)
  • Estimated number of complete threads required (—)
  • Smallest of the three comparison margins (—)

Fd=kF; As≈πdₘLe/3; Fh=Asτh; Fb=Asτb; Ft=Atσa; Lreq=3Fd/[πdₘ min(τh,τb)].

Empirical shear-area approximation for preliminary assessment of ordinary metal threads, not an exact JIS tolerance calculation. The 1/3 factor accounts approximately for imperfect mating. Verify pitch diameter and complete engagement, excluding chamfers and incomplete runout. F includes preload and the maximum in-service thread load, not external force alone. Independently establish allowables for material, temperature and design criteria. Thin-boss splitting, bending, fatigue, creep, inserts, plastic threads and individual-thread load distribution are not assessed.

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目的から順に確認する設計ガイド

図で条件を整理してから計算し、最後に実際の部品仕様を確認します。

Purpose-based design guides

Understand conditions with diagrams, calculate, then verify actual specifications.