{ "slug": "standard-tolerances", "title": "CNC部品の一般公差：ISO 2768とIT等級", "description": "四つの精密等級に応じたISO 2768一般公差、IT01からIT18までのIT等級、各CNC工程が実際に保証できる公差 — 図面に記載すべき等級とともに解説。", "lang": "ja", "tables": [ { "caption": "線形寸法のISO 2768-1一般公差（mm）", "columns": [ "呼び寸法範囲（mm）", "ISO 2768-f", "ISO 2768-m", "ISO 2768-c", "ISO 2768-v" ], "rows": [ { "呼び寸法範囲（mm）": "0.5 – 3", "ISO 2768-f": "±0.05", "ISO 2768-m": "±0.1", "ISO 2768-c": "±0.2", "ISO 2768-v": "—" }, { "呼び寸法範囲（mm）": "3 – 6", "ISO 2768-f": "±0.05", "ISO 2768-m": "±0.1", "ISO 2768-c": "±0.3", "ISO 2768-v": "±0.5" }, { "呼び寸法範囲（mm）": "6 – 30", "ISO 2768-f": "±0.1", "ISO 2768-m": "±0.2", "ISO 2768-c": "±0.5", "ISO 2768-v": "±1.0" }, { "呼び寸法範囲（mm）": "30 – 120", "ISO 2768-f": "±0.15", "ISO 2768-m": "±0.3", "ISO 2768-c": "±0.8", "ISO 2768-v": "±1.5" }, { "呼び寸法範囲（mm）": "120 – 400", "ISO 2768-f": "±0.2", "ISO 2768-m": "±0.5", "ISO 2768-c": "±1.2", "ISO 2768-v": "±2.5" }, { "呼び寸法範囲（mm）": "400 – 1000", "ISO 2768-f": "±0.3", "ISO 2768-m": "±0.8", "ISO 2768-c": "±2.0", "ISO 2768-v": "±4.0" }, { "呼び寸法範囲（mm）": "1000 – 2000", "ISO 2768-f": "±0.5", "ISO 2768-m": "±1.2", "ISO 2768-c": "±3.0", "ISO 2768-v": "±6.0" }, { "呼び寸法範囲（mm）": "2000 – 4000", "ISO 2768-f": "—", "ISO 2768-m": "±2.0", "ISO 2768-c": "±4.0", "ISO 2768-v": "±8.0" } ] }, { "caption": "どの精密等級を指定すべきか", "columns": [ "等級", "精度レベル", "典型的な用途", "コストへの影響" ], "rows": [ { "等級": "f (fine)", "精度レベル": "一般公差として最高の精度", "典型的な用途": "精密部品、特定のはめあいを要しない接合面、厳しい外観要求", "コストへの影響": "中級比 +15–30%" }, { "等級": "m (medium)", "精度レベル": "標準CNC", "典型的な用途": "一般的なCNC切削部品。最も広く使われる等級で、加工部品の大半に適合します。", "コストへの影響": "基準値" }, { "等級": "c (coarse)", "精度レベル": "緩い", "典型的な用途": "板金部品、構造用溶接物、非重要鋳物、大型アセンブリ", "コストへの影響": "中級比 −10–20%" }, { "等級": "v (very coarse)", "精度レベル": "最も緩い", "典型的な用途": "溶接構造、荒鋳物、非精密加工部品、非常に大きな寸法", "コストへの影響": "中級比 −20–35%" } ] }, { "caption": "IT等級 — 公差数値が意味するもの", "columns": [ "IT等級", "実務上の意味", "1–3 mm", "6–10 mm", "18–30 mm", "50–80 mm", "120–180 mm", "250–315 mm" ], "rows": [ { "IT等級": "IT01", "実務上の意味": "ブロックゲージ基準", "1–3 mm": "0.3", "6–10 mm": "0.4", "18–30 mm": "0.6", "50–80 mm": "0.8", "120–180 mm": "1.0", "250–315 mm": "1.2" }, { "IT等級": "IT0", "実務上の意味": "基準標準器", "1–3 mm": "0.5", "6–10 mm": "0.6", "18–30 mm": "0.9", "50–80 mm": "1.2", "120–180 mm": "1.5", "250–315 mm": "2.0" }, { "IT等級": "IT1", "実務上の意味": "精密ゲージ", "1–3 mm": "0.8", "6–10 mm": "1.0", "18–30 mm": "1.5", "50–80 mm": "2.0", "120–180 mm": "2.5", "250–315 mm": "3.0" }, { "IT等級": "IT2", "実務上の意味": "高精度ゲージ", "1–3 mm": "1.2", "6–10 mm": "1.5", "18–30 mm": "2.5", "50–80 mm": "3.0", "120–180 mm": "4.0", "250–315 mm": "5.0" }, { "IT等級": "IT3", "実務上の意味": "超精密加工", "1–3 mm": "2.0", "6–10 mm": "2.5", "18–30 mm": "4.0", "50–80 mm": "5.0", "120–180 mm": "6.0", "250–315 mm": "8.0" }, { "IT等級": "IT4", "実務上の意味": "精密研削／ワイヤEDM", "1–3 mm": "3", "6–10 mm": "4", "18–30 mm": "6", "50–80 mm": "8", "120–180 mm": "10", "250–315 mm": "13" }, { "IT等級": "IT5", "実務上の意味": "ゲージ製作", "1–3 mm": "4", "6–10 mm": "6", "18–30 mm": "9", "50–80 mm": "13", "120–180 mm": "16", "250–315 mm": "20" }, { "IT等級": "IT6", "実務上の意味": "精密機械加工", "1–3 mm": "6", "6–10 mm": "9", "18–30 mm": "13", "50–80 mm": "19", "120–180 mm": "25", "250–315 mm": "32" }, { "IT等級": "IT7", "実務上の意味": "精密はめあい（軸受・軸）", "1–3 mm": "10", "6–10 mm": "15", "18–30 mm": "21", "50–80 mm": "30", "120–180 mm": "40", "250–315 mm": "52" }, { "IT等級": "IT8", "実務上の意味": "一般精密機械加工", "1–3 mm": "14", "6–10 mm": "22", "18–30 mm": "33", "50–80 mm": "46", "120–180 mm": "63", "250–315 mm": "81" }, { "IT等級": "IT9", "実務上の意味": "一般機械加工（ISO 2768-m相当）", "1–3 mm": "25", "6–10 mm": "36", "18–30 mm": "52", "50–80 mm": "74", "120–180 mm": "100", "250–315 mm": "130" }, { "IT等級": "IT10", "実務上の意味": "中精度", "1–3 mm": "40", "6–10 mm": "58", "18–30 mm": "84", "50–80 mm": "120", "120–180 mm": "160", "250–315 mm": "210" }, { "IT等級": "IT11", "実務上の意味": "緩い公差の機械加工", "1–3 mm": "60", "6–10 mm": "90", "18–30 mm": "130", "50–80 mm": "190", "120–180 mm": "250", "250–315 mm": "320" }, { "IT等級": "IT12", "実務上の意味": "極めて荒い機械加工", "1–3 mm": "100", "6–10 mm": "150", "18–30 mm": "210", "50–80 mm": "300", "120–180 mm": "400", "250–315 mm": "500" }, { "IT等級": "IT13", "実務上の意味": "木型製作と荒加工", "1–3 mm": "140", "6–10 mm": "220", "18–30 mm": "310", "50–80 mm": "440", "120–180 mm": "580", "250–315 mm": "740" }, { "IT等級": "IT14", "実務上の意味": "粗い低品質作業", "1–3 mm": "250", "6–10 mm": "370", "18–30 mm": "520", "50–80 mm": "740", "120–180 mm": "1000", "250–315 mm": "1250" }, { "IT等級": "IT15", "実務上の意味": "非常に粗い", "1–3 mm": "400", "6–10 mm": "600", "18–30 mm": "840", "50–80 mm": "1200", "120–180 mm": "1600", "250–315 mm": "2000" }, { "IT等級": "IT16", "実務上の意味": "概略／未指定", "1–3 mm": "600", "6–10 mm": "1000", "18–30 mm": "1400", "50–80 mm": "2000", "120–180 mm": "2600", "250–315 mm": "3200" }, { "IT等級": "IT17", "実務上の意味": "極めて概略的", "1–3 mm": "1000", "6–10 mm": "1600", "18–30 mm": "2400", "50–80 mm": "3300", "120–180 mm": "4300", "250–315 mm": "5300" }, { "IT等級": "IT18", "実務上の意味": "一般製作作業", "1–3 mm": "1400", "6–10 mm": "2500", "18–30 mm": "3500", "50–80 mm": "4800", "120–180 mm": "6300", "250–315 mm": "7600" } ] }, { "caption": "各CNC工程が実際に保証できる公差", "columns": [ "工程", "標準（代表的）", "精密（追加コスト）", "超精密（高コスト）", "IT相当" ], "rows": [ { "工程": "CNC Milling (3-axis)", "標準（代表的）": "±0.025mm", "精密（追加コスト）": "±0.005mm", "超精密（高コスト）": "±0.002mm", "IT相当": "IT8 → IT5 → IT3" }, { "工程": "CNC Milling (5-axis)", "標準（代表的）": "±0.010mm", "精密（追加コスト）": "±0.005mm", "超精密（高コスト）": "±0.002mm", "IT相当": "IT7 → IT5 → IT3" }, { "工程": "CNC Turning", "標準（代表的）": "±0.025mm", "精密（追加コスト）": "±0.005mm", "超精密（高コスト）": "±0.002mm", "IT相当": "IT8 → IT5 → IT3" }, { "工程": "Swiss-Type Turning", "標準（代表的）": "±0.010mm", "精密（追加コスト）": "±0.005mm", "超精密（高コスト）": "±0.002mm", "IT相当": "IT7 → IT5 → IT3" }, { "工程": "Surface Grinding", "標準（代表的）": "±0.005mm", "精密（追加コスト）": "±0.002mm", "超精密（高コスト）": "±0.001mm", "IT相当": "IT5 → IT3 → IT2" }, { "工程": "Jig Boring", "標準（代表的）": "±0.010mm", "精密（追加コスト）": "±0.005mm", "超精密（高コスト）": "±0.002mm", "IT相当": "IT7 → IT5 → IT3" }, { "工程": "Wire EDM", "標準（代表的）": "±0.010mm", "精密（追加コスト）": "±0.003mm", "超精密（高コスト）": "±0.001mm", "IT相当": "IT7 → IT4 → IT2" }, { "工程": "Sinker EDM", "標準（代表的）": "±0.015mm", "精密（追加コスト）": "±0.005mm", "超精密（高コスト）": "±0.002mm", "IT相当": "IT8 → IT5 → IT3" } ] } ] }