挤压丝攻底孔对照表如下：
| 螺牙尺寸 | M1.6 | M2 | M2.5 | M3 | M4 | M5 | M6 | M8 | M10 | M12 | M14 | M16 | M18 | M20 | M22 | M24 | M27 |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 底孔尺寸 | 1.45±0.02 | 1.80±0.02 | 2.30±0.02 | 2.75±0.03 | 3.65±0.03 | 4.60±0.03 | 5.55±0.04 | 7.40±0.04 | 9.30±0.05 | 11.10±0.05 | 13.10±0.05 | 15.10±0.05 | 16.90±0.05 | 18.90±0.05 | 20.90±0.05 | 22.65±0.05 | 25.65±0.05 |
备注：
1. 切削攻牙前底孔尺寸 = 螺牙尺寸 * 0.85
2. 挤压攻牙前底孔尺寸 = 螺牙尺寸 * 0.91
3. 预冲孔 = 螺牙尺寸 * 0.5
4. 切削攻牙后底孔尺寸 = 螺牙尺寸 * 0.86
5. 挤压攻牙后内孔尺寸 = 螺牙尺寸 * 0.88
这些数据适用于不同材质如不锈钢（Al、SECC、SGCC等）的挤压丝攻攻牙底孔尺寸。公差值分别为：±0.02、±0.03、±0.04、±0.05等。请根据具体应用需求选择合适的底孔尺寸。