Introduction to Liner & Nut for American-Style Ferrule Fittings (Eaton Standard NB200 & NB300)
Publish Time: 2026-04-14 Origin: Site
1. Basic Definition & Function
Eaton Standard NB200 / NB300 are core components of American JIC 37° Triple-Lok hydraulic tube fittings, with clear division of labor to ensure stable sealing and connection:
NB200: Nut — Hexagonal head with internal thread, mainly used for tightening and applying pressure to secure the fitting assembly.
NB300: Sleeve / Front Ferrule — Ring-shaped ferrule with a sharp cutting edge; when tightened, it bites into the tube wall to achieve reliable sealing and gripping.
2. NB200 Nut (American JIC Standard)
Standard: Eaton / Aeroquip, compliant with JIC B-1
Thread: UNF American fine thread (e.g., 7/16-20, 1/2-20, 9/16-18, etc.)
Material: Carbon steel (zinc-plated / black oxide), stainless steel 304/316
Core Functions:
Transmits torque and axially compresses the NB300 sleeve
Engages with the fitting body thread to fix the tubing firmly
Prevents loosening and resists vibration in harsh working environments
Common Sizes (Inch): Matching the outer diameter of hydraulic tubes, with size codes corresponding to tube specifications (detailed in the size matching table below).
3. NB300 Sleeve (Front Ferrule)
Standard: Eaton Triple-Lok JIC 37°
Structure: Single front ferrule with internal cutting edge and external 37° cone (matches JIC fitting body)
Material: High-carbon steel, hardened stainless steel (for wear and corrosion resistance)
Sealing Principle:
Nut tightening → pushes the NB300 sleeve forward
External 37° cone mates with the fitting body’s 37° cone → forms face sealing
Internal cutting edge bites into the outer tube wall → achieves dual effect of gripping and radial sealing
Vibration-resistant and high-pressure rated (up to approximately 40MPa)
Matching Rule: NB300-XX must match NB200-XX of the same size. Example: 1/4" tube → NB200-04 Nut + NB300-04 Sleeve
4. Size Matching Table (NB200 & NB300)
Tube Outer Diameter (Inch) |
NB200 Nut Model |
NB300 Sleeve Model |
Corresponding Thread (UNF) |
|---|---|---|---|
1/4" |
NB200-04 |
NB300-04 |
7/16-20 |
3/8" |
NB200-06 |
NB300-06 |
9/16-18 |
1/2" |
NB200-08 |
NB300-08 |
3/4-16 |
5/8" |
NB200-10 |
NB300-10 |
1-14 |
3/4" |
NB200-12 |
NB300-12 |
1-1/8-12 |
1" |
NB200-16 |
NB300-16 |
1-1/4-12 |
5. Features of American JIC Triple-Lok Fittings (vs. Metric 24° Cone)
Item |
American JIC 37° (NB200/NB300) |
Metric 24° Cone (DIN) |
|---|---|---|
Sealing Surface |
37° external cone |
24° internal cone |
Structure |
Single ferrule (NB300) design (some with rear ferrules) |
Dual ferrule design |
Thread |
UNF American fine thread |
Metric thread |
Application |
Hydraulic systems, oil & gas, construction machinery, marine (US-standard equipment) |
European/Asian standard hydraulic equipment |
6. Selection & Installation Notes
6.1 Selection Tips
Size Matching: The last two digits of NB200/NB300 models correspond to the tube outer diameter (e.g., 04 = 1/4", 06 = 3/8").
Material Selection: Carbon steel for general working environments; stainless steel 304/316 for corrosive environments (e.g., marine, chemical industry).
6.2 Installation Steps & Notes
Prepare the tube: Ensure tube ends are smooth, burr-free, and cut vertically (no bevel).
Assemble components: First install the NB200 nut onto the tube, then slide the NB300 sleeve (cutting edge facing the fitting body).
Tighten: Hand-tighten the nut fully until it contacts the fitting body, then use a wrench to turn 1 to 1¼ turns (adjust according to tube size).
Inspect: After installation, check that the sleeve is fully bitten into the tube wall and there is no leakage under pressure.