Brass compression sleeves – also called ferrules – are the ring that bites into the tube outside as the compression nut is tightened, forming the seal of the joint. This page covers the sleeve only – the fitting body and nut are ordered separately. For a complete metric fitting, see our metric compression straight tube fittings; for tool-free grease lines, see push-to-connect grease line fittings; and for imperial micro-bore runs, see 1/8 inch tube x 1/4-28 UNF compression fittings.
Ferrule Designs and Pressure Ratings
Three designs cover most centralized lubrication lines: single ferrule for ordinary oil and grease lines, double ferrule for higher pressures, and the Heavy-Duty Series for the most demanding grease lines. Working pressure, declared burst rating, and service temperature are listed below.
| Design | Working Pressure | Declared Burst Rating | Service Temperature |
|---|---|---|---|
| Single ferrule | 150 bar (2,175 PSI) | 600 bar (8,700 PSI) | -20°C to +120°C |
| Double ferrule | 400 bar (5,800 PSI) | 1,600 bar (23,200 PSI) | -40°C to +150°C |
| Heavy-Duty Series | 630 bar (9,135 PSI) | 2,520 bar (36,540 PSI) | -40°C to +175°C |
Material, Strength, and Surface Finish
Sleeves are machined from CuZn39Pb3 brass, also named CW614N: minimum tensile 380 MPa (55,000 PSI), minimum yield 180 MPa (26,000 PSI), hardness 80 – 120 HV, sealing surface Ra 1.6 micron. Standard finish is natural brass; nickel plating of 5 – 8 micron is available, and lead-free CW511L or CW602N on request.
Installation: Tightening Turns and Torque
Hand-tighten the nut, then turn it through the first-assembly range while holding the body with a backup wrench; re-assembly uses the smaller range with a new sleeve. Turns by tube outside diameter:
| Tube OD | First Assembly | Re-Assembly |
|---|---|---|
| 4 – 6 mm (1/8″ – 3/16″) | 1-1/4 turns | 1/4 turn |
| 8 – 10 mm (1/4″ – 3/8″) | 1-1/4 turns | 1/4 – 1/2 turn |
| 12 – 16 mm (1/2″ – 5/8″) | 1 turn | 1/4 – 1/2 turn |
| 18 – 25 mm (3/4″ – 1″) | 3/4 – 1 turn | 1/4 turn |
With a torque wrench, tighten to the initial then final value, holding the backup wrench on the flats listed:
| Tube OD | Initial Torque | Final Torque | Backup Wrench Flats |
|---|---|---|---|
| 6 mm | 10 – 12 Nm | 18 – 22 Nm | 14 / 17 mm |
| 8 mm | 15 – 18 Nm | 25 – 30 Nm | 17 / 19 mm |
| 10 mm | 20 – 25 Nm | 35 – 42 Nm | 17 / 19 mm |
| 12 mm | 30 – 35 Nm | 50 – 60 Nm | 22 / 27 mm |
| 16 mm | 45 – 50 Nm | 70 – 85 Nm | 27 / 30 mm |
| 20 mm | 60 – 70 Nm | 95 – 115 Nm | 30 / 36 mm |
Tube Compatibility and Wall Thickness
The sleeve grips metal tube directly within the wall ranges below. Plastic tubing always needs an internal tube support insert so the bore does not collapse.
| Tube Material | Compatible Wall Thickness | Notes |
|---|---|---|
| Copper | 0.8 – 2.0 mm | No insert required |
| Brass | 1.0 – 2.5 mm | No insert required |
| Aluminum | 1.0 – 2.0 mm | No insert required |
| Mild steel | 1.0 – 3.0 mm | No insert required |
| SS304 / SS316 | 1.5 – 3.0 mm | No insert required |
| PA66 nylon | 1.5 – 2.5 mm | Insert required; 120°C continuous limit |
| PA12 | 1.5 – 3.0 mm | Insert required; flexible to -40°C |
| PU | 2.0 – 3.5 mm | Insert required; 80°C limit |
For a ready-made PA12 line, see our PA12 tubing in a 6 x 1.5 mm wall.
What Is Supplied
Supply is the sleeves themselves, in the design and size ordered. Bodies, nuts, and support inserts are separate line items, so you stock the component that wears out, not whole fittings. Each sleeve is inspected for finish and size before packing.
Limitations and Ordering Notes
- A sleeve alone does not complete a joint; the body and nut must match the same tube outside diameter and thread form.
- A compressed sleeve is permanently deformed; fit a new one when a joint is opened.
- Plastic tubing (PA66, PA12, PU) needs a support insert, or the sleeve squeezes it shut.
Thread forms and sealing arrangements vary between families; confirm the thread form and sealing arrangement when ordering. Unsure which sleeve fits? ask our engineers to confirm the sleeve size.
Frequently Asked Questions
Do you sell the complete fitting, or only the ferrule?
Only the ferrule – the sleeve by itself; body and nut are ordered separately. Choose our metric compression straight tube fittings for a complete joint, our push-to-connect grease line fittings for tool-free lines, and the 1/8 inch tube x 1/4-28 UNF compression fitting page for imperial micro-bore runs.
Is a ferrule the same thing as a compression sleeve?
Yes. Both names describe the same ring-shaped sealing component; ferrule is the catalog term, compression sleeve describes its job.
How do I choose the right sleeve size?
Match the sleeve to the tube outside diameter, not the thread. Groups run from 4 – 6 mm to 18 – 25 mm tubing; sleeve, body, and nut must share the same group.
Can I use plastic tubing with these sleeves?
Yes, but only with an internal tube support insert. PA66: 1.5 – 2.5 mm wall, 120°C limit; PA12: 1.5 – 3.0 mm wall, flexible to -40°C; PU: 2.0 – 3.5 mm wall, 80°C limit. Our PA12 tubing in a 6 x 1.5 mm wall pairs with these sleeves.
Can I reuse a sleeve after taking the joint apart?
No. The sleeve deforms permanently during tightening to lock onto the tube; fit a new sleeve whenever a joint is opened.
How tight should I tighten the nut?
Use the first-assembly turns or initial-to-final torque values above, holding the body with a backup wrench on the listed flats; extra turns distort the tube.
The joint weeps slightly after assembly – what should I check?
Check that the tube end is square, deburred, and fully bottomed, then confirm final torque. If it still weeps, cut back the tube end and fit a new sleeve.
Should I choose brass or stainless steel sleeves?
Brass sleeves cover most oil and grease lines and are what this page supplies. In corrosive atmospheres, confirm sleeve and fitting material together when ordering.
What finishes and lead-free options are available?
Natural brass is standard. Nickel plating of 5 – 8 micron adds surface protection, and lead-free CW511L or CW602N is available on request.
Who makes these sleeves, and how do I order?
IsoHiTech Lubrication Systems, founded in 2023, engineering since 2006, manufactures these sleeves for centralized lubrication lines. To request a quotation or confirm sizing, write to inquiry@isohitech.com.
