美制外螺纹（2A）常用规格极限尺寸表（粗牙）公称尺寸螺纹系列代大径极限中径极限螺胚直径和每英寸牙数最、最大最、最大小径 max最小最大8-320.15710.16310.13990.14280.12483.583.61(0.164-32)3.99034.14273.55353.62713.169910-240.18180.18900.15860.16190.13794.074.10(0.190-24)4.61774.80064.02844.11233.502712-240.20780.21500.18450.18790.16394.724.75(0.216-24)5.27815.46104.68634.77274.16311/4-200.24080.24890.21270.21640.18765.455.48(0.250-20)6.11636.32215.40265.49664.76505/16-180.30260.31130.27120.27520.24316.946.98(0.3175-18)7.68607.90706.88856.99016.17473/8-160.36430.37370.32870.33310.29708.408.44(0.375-16)9.25329.49208.34908.46077.54387/16-14UNC0.42580.43610.38500.38970.34859.839.87(0.4375-14)10.815311.07699.77909.89848.85191/2-130.48760.49850.44350.44850.404111.3411.38(0.50-13)12.385012.661911.264911.391910.26419/16-120.54950.56090.50160.50680.458712.8012.84(0.5625-12)13.957314.246912.740612.872711.65105/8-110.61130.62340.55890.56440.511914.2714.32(0.625-11)15.527015.834414.196114.335813.00233/4-100.73530.74820.67730.68320.625517.2817.33(0.750-10)18.676619.004317.203417.353315.88777/8-90.85920.87310.79460.80090.736820.2720.32(0.875-9)21.823722.176720.182820.342918.71471"-80.98300.99800.91000.91680.844623.2223.27(1.000-8)24.968225.349223.114023.286721.45281. 螺胚直径指滚丝前的尺寸，数值为依经验公式计算而得，在实践中需验证。2. 标记示例：10-24UNC-2A（或 0.190-24UNC-2A）、3/8-16UNC-2A（或 0.375-16UNC-2A）（注：表中上行斜体数值单位为英寸，下行为毫米）美制外螺纹（2A）常用规格极限尺寸表（细牙）公称尺寸和螺纹系大径极限中径极限［、径螺胚直径每英寸牙数列代号最小最大最小最大最小最大8-360.15770.16320.14240.14520.1293.653.67(0.164-36)4.00564.14533.61703.68813.279110-320.18310.18910.16580.16880.15084.244.27(0.190-32)4.65074.80314.21134.28753.830312-280.20850.21500.18860.19180.17124.824.85(0.216-28)5.29595.46104.79044.87174.34851/4-280.24250.24900.22250.22580.20525.695.71(0.250-28)6.15956.32465.65155.73535.21215/16-240.30420.31140.28060.28430.26037.177.20(0.3175-24)7.72677.90967.12727...
