Brass Compression Bushing & Tube Sleeves for Lubrication Lines
On this page, compression bushing means the brass ferrule-style sleeve that grips nylon or metal tubing inside a compression nut—not a rotating machine bearing. These parts work with compression fittings and lubrication couplings to seal 4 mm, 6 mm, and 8 mm lines in PDI oil and low-pressure grease circuits.
IsoHiTech supplies threaded compression bushings (30007 / 30008 / 30094), plain sleeves (30091 / 30001 / 30002), and nylon tube inserts (30010 / 30013 / 30041) for field repair and OEM builds.
What These Parts Do in a Lubrication Circuit
In central lubrication, a compression bushing (also called a compression sleeve or olive) sits between the tube and the fitting body. When the nut tightens, the bushing compresses radially on the tube OD and axially against the fitting seat—creating a metal-to-metal and metal-to-tube seal without solder.
Typical locations:
- Branch take-offs from single-line or positive injector mains
- Transitions from rigid nylon to flexible hose
- Service loops near injectors and pump outlets
Not the same as: sintered brass bearing bushings used in pivots and slides. If you need bearing selection, see bearing database; this page covers plumbing hardware for lube lines only.
Product Families on This Page
| Type | P/N examples | Spec | Use |
|---|---|---|---|
| Compression bushing | 30007 | M8 × 4 mm tube | Small metric compression joint |
| Compression bushing | 30008 | M10 × 6 mm | Standard injector branch |
| Compression bushing | 30094 | M12 × 8 mm | Larger secondary line |
| Sleeve | 30091 / 30001 / 30002 | 4 / 6 / 8 mm ID | Support sleeve, ferrule backup |
| Nylon tube insert | 30010 / 30013 / 30041 | 4 / 6 / 8 mm hose | Stiffen soft tube for collet or compression |
Benefits of Using Brass Compression Bushings
Why Brass for Lubrication Compression Parts
- Corrosion resistance — tolerates oil, most greases, and shop moisture better than plain steel olives.
- Controlled deformation — brass bushing compresses evenly on nylon PA11/PA12 without cracking like harder steels on soft tube.
- Reusability — in service work, bushings can often be replaced once while reusing the fitting body (inspect for groove damage).
- Compatibility — pairs with metric and pipe-thread bodies listed on straight, elbow, and reducer couplings.
When to Add a Nylon Tube Insert
Soft-wall tubing collapses under collet or single-ferrule compression. Inserts (30010 / 30013 / 30041) restore round bore and prevent flow restriction—especially with quick-plug elbows and long horizontal runs.
Lubrication Techniques for Brass Compression Bushings
Assembly Procedure (Compression Bushing)
- Cut tube square; deburr OD and chamfer lightly.
- Slide nut → bushing/sleeve → tube insert (if used) onto tube in correct order.
- Insert tube fully into fitting body until it bottoms on the seat.
- Hand-tighten nut, then wrench ¼–½ turn beyond hand-tight for nylon (do not over-crush).
- Pressure-test at 1.25× working pressure before full system start.
Torque & Tube Pairing
| Tube OD | Typical bushing P/N | Notes |
|---|---|---|
| 4 mm | 30007 / 30091 / 30010 | Use insert on soft nylon; clip every 300 mm |
| 6 mm | 30008 / 30001 / 30013 | Most common PDI branch size |
| 8 mm | 30094 / 30002 / 30041 | Check pump port thread before ordering |
Related Components
- Compression fittings catalog — straight, elbow, swing bodies
- Lubrication pipe guide — material and bend radius
- Pipe clips — reduce vibration loosening
- Coupling hub — threaded alternatives to compression
Troubleshooting
| Symptom | Likely cause | Action |
|---|---|---|
| Weep at nut | Under-torque, damaged bushing | Retighten; replace bushing once |
| Crushed tube | Over-torque, missing insert | Cut back tube; add insert; new olive |
| Intermittent blockage | Oval tube, wrong OD bushing | Match 4/6/8 mm P/N exactly |
| Nut spins free | Stripped threads or wrong nut | Replace fitting body set |
Quote bushing kits with your fitting list: contact for a quote.
Before you buy: read our grease fitting types guide.
A brass sleeve compressed by a fitting nut to seal rigid or semi-rigid tubing on a lubrication line. It is not a rotating bearing bushing.
Use compression bushing 30008 (M10 × 6 mm). Add sleeve 30001 or insert 30013 if tube is soft nylon.
Often once if grooves are intact. Replace after every disassembly on critical high-pressure legs.
Yes for soft nylon and long spans—inserts 30010 (4 mm), 30013 (6 mm), 30041 (8 mm) prevent collapse.
Compression suits field-cut tube lengths; threaded couplings suit factory-fixed ports and higher torque sealing.
No. This page covers tube compression hardware. For bearing part numbers see bearing database.
Depends on fitting body and tube—typical PDI oil branches are low to moderate pressure. Confirm with your pump datasheet; use heavy-wall tube for grease secondaries.
They support or back up compression on 4 / 6 / 8 mm tube when the fitting design calls for a two-piece olive stack.
Clamp within 50 mm of the joint using pipe clips; avoid unsupported long branches.