精度選定SNT 依母螺紋之等級(1、2、3級等)決定螺絲攻之精度表1. 公制螺紋(M) 表2. 美制螺紋(U)規 格牙距螺 絲 攻 精 度規 格牙數螺 絲 攻 精 度1級母螺紋2級母螺紋1級母螺紋2級母螺紋M3 M4 M4.5 M5 M5.50.5GH3GH4GH5GH6No.544GH3GH4GH5GH6M3 M3.50.35GH3GH4GH5GH6No.5 No.640GH3GH4GH5GH6M3.50.6GH3GH4GH5GH6No.836GH4GH5GH6M40.7GH4GH5GH6GH7No.6 No.8 No.10 32GH4GH5GH6M50.8GH4GH5GH6GH7No.10 No.1224GH4GH5GH6M61GH4GH5GH6GH7No.1228GH4GH5GH6M4 M4.5 M60.75GH4GH5GH6GH7U 1/420GH4GH5GH6GH7M7 M8 M91GH4GH5GH6GH728GH4GH5GH6M10 M110.75GH4GH5GH6GH7U 5/1618GH5GH6GH7GH8M10 M11 M121GH4GH6GH7GH824GH5GH6GH7M8 M9 M10 M121.25GH5GH6GH7GH8U 3/816GH5GH6GH7GH8M10 M11 M121.5GH5GH6GH7GH824GH5GH6GH7M121.75GH5GH7GH8GH9U 7/1614GH5GH6GH7GH8M14 M15 M161GH5GH6GH7GH820GH5GH6GH7GH8M17 M18 M20 M22 M24 1GH5GH6GH7GH8U 1/213GH6GH7GH8GH9M14 M15 M161.5GH5GH7GH8GH920GH5GH6GH7GH8M18 M20 M22 M24 1.5GH6GH7GH8GH9U 9/1612GH6GH7GH8GH9M14 M162GH6GH7GH8GH918GH6GH7GH8GH9M171.5GH6GH8GH9GH10U 5/811GH7GH8GH9GH10M18 M20 M22 2GH6GH8GH9GH1018GH6GH7GH8GH9M18 M20 M22 2.5GH6GH8GH9GH10U 3/410GH7GH8GH9GH10M242GH6GH8GH9GH1016GH6GH7GH8GH9M243GH6GH8GH9GH10U 7/89GH7GH8GH9GH1014GH6GH7GH8GH9U 18GH8GH9GH10GH1112GH7GH8GH9GH10表3. 英制螺紋(W)規 格牙數螺 絲 攻 精 度備註:(1)各等級之文字大者為參考用標準精度，視加工材及作業條件之適用情況，可選擇前後項的精度而變更之。 (2)表1.2.3確定之絲攻精度其公差12.7um(0.0005)的階段狀公差。 GH6時為12.76=77um為上限容許差，下限容許差則為77-12.7(13)=64um1級母螺紋2級母螺紋W 1/8 44GH3GH4GH5GH6W 5/3240GH3GH4GH5GH6W 3/2436GH4GH5GH6W 1/420GH4GH5GH6GH7W 5/1618GH5GH6GH7GH8W 3/816GH5GH6GH7GH8W 7/1614GH5GH6GH7GH8W 1/212GH6GH7GH8GH9W 9/1612GH6GH7GH8GH9W 5/811GH7GH8GH9GH10W 3/410GH7GH8GH9GH10W 7/89GH7GH8GH9GH10W 18GH8GH9GH10GH112.加工材攻牙速度與攻牙油選定基準螺 帽 種 類切削速度 m/min切削油劑切削速度計算式：螺帽冷間成型軟材2535 V = D N硬材20301000螺帽熱間成型軟材2535不水溶性切削油硬材2030V：切削速度(m/min) 螺帽經熱處理調質2530HRC2535D：TAP外徑(mm)3036HRC1020N：迴轉速(r.p.m)不 銹 鋼 螺 帽15253.螺帽絲攻形狀 M7(U1/4)以下 M8(U5/16)以上表1.公制普通牙 表2.公制細牙規 格A(全長)B(牙長)C(柄徑)刃數規 格A(全長)B(牙長)C(柄徑)刃數25山30山(SUS)25山30山(SUS)M3 0.558.712.5152.33M4 0.558.112.51533M3.5 0.658.515182.33M5 0.562.612.51543M4 0.758.317.52133M6 0.7567.218.822.54.53M4.5 0.755818.822.53.53M7 0.757018.822.55.53M5 0.862.820243.83M8 0.757618.822.56.55M6 167.425304.63M9 0.758918.822.57.55M7 17025305.63M8 17725306.65M8 1.257731.337.565M9 18925307.65M9 1.258931.337.575M10 18925308.65M10 1.58937.54585M10 1.258931.337.585M11 1.510237.5458.85M12 1.2510231.337.5105M12 1.7510243.852.59.55M14 1.2511431.337.5125M14 2114506011.25M12 1.510237.5459.55M16 2127506013.15M14 1.511437.54511.25M18 2.513362.575145M16 1.512737.54513.15M20 2.513362.57516.55M18 1.513337.545155M22 2.514662.57517.55M20 1.513337.54516.55M24 3165759018.55M22 1.514637.545195M27 3165759021.55M24 1.516537.54521.55M18 21335060155表3.美制普通牙M20 2133506016.55M22 21465060195規 格A(全長)B(牙長)C(柄徑)刃數M24 2165506020525山30山(SUS)No. 4-40UNC58.815.919.123表4.美制細牙No. 5-40UNC58.715.919.12.23No. 6-32UNC58.619.823.82.43規 格A(全長)B(牙長)C(柄徑)刃數No. 8-32UNC58.21