NPT/NPTF 為60°牙型；BSPT/BSPP 為55°惠氏牙型。NPT 與 BSP 不可互換。
管螺紋與攻牙底孔指南
NPT/NPTF 為60°牙型；BSPT/BSPP 為55°惠氏牙型。NPT 與 BSP 不可互換。
NPTF 靠受控的牙頂牙底干涉密封；底孔依絲攻廠商規定。NPT/BSPT 通常需密封劑；BSPP/G 靠墊圈或 O 形環密封。
tapered · 60°
NPT
| 套筒 · 尺寸 | 螺紋 · 尺寸 | TPI | ° | 攻牙底孔 |
|---|---|---|---|---|
| 1/8 in. | 0.405 in. | 27 TPI | 60° | Q · 0.332 in. |
| 1/4 in. | 0.540 in. | 18 TPI | 60° | 7/16 in. |
| 3/8 in. | 0.675 in. | 18 TPI | 60° | 9/16 in. |
| 1/2 in. | 0.840 in. | 14 TPI | 60° | 45/64 in. |
tapered · 60°
NPTF
| 套筒 · 尺寸 | 螺紋 · 尺寸 | TPI | ° | 攻牙底孔 |
|---|---|---|---|---|
| 1/8 in. | 0.405 in. | 27 TPI | 60° | — |
| 1/4 in. | 0.540 in. | 18 TPI | 60° | — |
| 3/8 in. | 0.675 in. | 18 TPI | 60° | — |
| 1/2 in. | 0.840 in. | 14 TPI | 60° | — |
tapered · 55°
BSPT · R
| 套筒 · 尺寸 | 螺紋 · 尺寸 | TPI | ° | 攻牙底孔 |
|---|---|---|---|---|
| 1/8 in. | 0.383 in. | 28 TPI | 55° | 8.4 mm |
| 1/4 in. | 0.518 in. | 19 TPI | 55° | 11.2 mm |
| 3/8 in. | 0.656 in. | 19 TPI | 55° | 14.75 mm |
| 1/2 in. | 0.825 in. | 14 TPI | 55° | 18.25 mm |
parallel · 55°
BSPP · G
| 套筒 · 尺寸 | 螺紋 · 尺寸 | TPI | ° | 攻牙底孔 |
|---|---|---|---|---|
| 1/8 in. | 0.383 in. | 28 TPI | 55° | 8.8 mm |
| 1/4 in. | 0.518 in. | 19 TPI | 55° | 11.8 mm |
| 3/8 in. | 0.656 in. | 19 TPI | 55° | 15.25 mm |
| 1/2 in. | 0.825 in. | 14 TPI | 55° | 19.0 mm |
表列底孔僅供切削絲攻起始參考，請核對材料與廠商要求。