What Grease Nipple Extension Fittings Do
A grease nipple extension fitting relocates a grease point from a confined, guarded, or buried bearing location to a spot the grease gun can access. The nipple stays on the bearing; the extension carries grease through a rigid pipe, a high-pressure flexible hose, or an angle adapter, rated for continuous working pressure up to 5,000 PSI (345 bar). US parts lists call the same hardware a grease fitting extension or grease fitting extension tube – nipple and fitting are regional names for the same zerk-standard end. For length selection and routing rules, see the grease nipple extension guide. For choosing the nipple itself, see the grease fitting types guide.
Three Types of Extension Fittings
Rigid Extension Pipes
Straight threaded-end tubes in lengths from 0.5″ to 6″ (20mm to 150mm), in carbon steel with zinc plating, stainless steel 316, or brass; they suit short, straight paths behind guards or frame members.
High-Pressure Hose Extensions
Flexible hose assemblies with fittings at both ends, in 5″, 12″, 20″, and 30″ lengths, custom available. They route around moving parts and hinge lines where rigid pipe would fatigue, at lower flow. For hose beyond extensions, see the high-pressure hose range.
Angle and Swivel Adapters
45° and 90° elbows change the direction of a grease point in tight spaces; swivel and union styles serve access from more than one direction without adding length. Every added joint is another potential leak point.
Technical Specifications
Threads: BSPP (ISO 228-1), NPT, M6x1, M8x1, M10x1, and UNF; dimensions follow DIN 71412. Seals: NBR for petroleum greases, FKM (Viton) for synthetic greases and high temperature, silicone for low temperature, EPDM for chemical resistance.
| Material | Continuous Pressure | Temperature Range | Typical Use |
|---|---|---|---|
| Carbon steel, zinc-plated | 5,000 PSI | -40°C to +120°C | Indoor and mild outdoor industrial service |
| Stainless steel 316 | 5,000 PSI | -40°C to +204°C | Corrosive or washdown and chemical environments |
| Brass | 3,000 PSI | -20°C to +150°C | Pneumatic circuits and non-sparking areas |
| Composite | 4,000 PSI | -40°C to +120°C | Weight-sensitive or electrical-isolation needs |
Grease flow runs up to 25 cc/min through rigid extensions and 15-20 cc/min through hose extensions, varying with ID and length. Unit weight runs from 15 g (20mm rigid) to 180 g (300mm hose assembly).
| Thread | Install Torque | Sealant |
|---|---|---|
| M6x1 | 5-7 Nm | PTFE tape, 2-3 wraps |
| M8x1 | 8-12 Nm | PTFE tape, 2-3 wraps |
| M10x1 | 15-20 Nm | PTFE tape, 2-3 wraps |
| 1/8″ BSPP | 6-9 Nm | PTFE tape, 2-3 wraps |
| 1/4″ NPT | 12-18 Nm | Thread sealant compound |
Installation and Flow Notes
- Clean threads and confirm the thread standard; a mismatched thread leaks even at correct torque.
- Pre-fill flexible hose extensions with NLGI 2 grease before installation so air pockets cannot block flow.
- Keep hose bend radius at least 6x the hose diameter; support the hose every 12-18 in so vibration does not fatigue the ends.
- Longer or smaller-ID extensions flow less; a very long run may need a higher-output pump to deliver the same grease at the bearing.
For standard or custom lengths, send thread size, length, and material through the quote request page.
Where Extension Fittings Are Used
- Conveyor bearings behind guards and press lubrication points inside frames.
- Excavator pins under boom assemblies and points buried in linkage clusters.
- Chassis points blocked by exhaust routing, where the extension moves greasing away from hot surfaces.
- Agricultural implement bearings sitting inside crop residue areas.
- Gang lubrication, where several points are extended to one service location for a one-pass round.
Extension fittings belong to the wider lubrication accessories family.
Frequently Asked Questions
What is a grease nipple extension fitting and when is one needed?
It moves a grease point to an accessible position while the nipple stays on the bearing. You need one when guards or parts block grease gun access, or to group several points for faster rounds: rigid pipe for straight paths, hose around moving parts, angle adapter to change direction.
What types and lengths are available?
Rigid pipes from 0.5″ to 6″ (20mm to 150mm), hose extensions in 5″, 12″, 20″, and 30″ plus custom lengths, and 45° or 90° angle adapters in fixed and swivel styles.
Which thread standards are offered?
BSPP per ISO 228-1, NPT, M6x1, M8x1, and M10x1, and UNF; dimensions follow DIN 71412 so the coupler still fits.
What is the maximum working pressure?
Carbon steel and stainless 316 carry 5,000 PSI continuous, with short-duration burst to 8,000 PSI. Brass is rated 3,000 PSI and composite 4,000 PSI. Keep gun output within the lowest-rated part.
How do I pick the right material?
Zinc-plated carbon steel for indoor and mild outdoor service. Stainless 316 for corrosive or washdown and chemical environments. Brass for pneumatic circuits at moderate pressure. Composite for weight-sensitive installs; avoid impact-prone spots.
Which seal material should I choose?
NBR for petroleum-based greases, FKM (Viton) for synthetic greases and high temperature, silicone for low temperature, EPDM where chemical exposure dominates. Match the seal to the grease.
How much grease flows through an extension?
Up to 25 cc/min through rigid extensions and 15-20 cc/min through hose extensions, varying with ID and length. Longer or smaller-ID runs flow less; confirm grease arrives on the first fill.
How do I stop air pockets in a hose extension?
Pre-fill the hose with NLGI 2 grease before installation so air is pushed out first. Keep bends above 6x the hose diameter and support the hose every 12-18 in.
Do angle adapters and swivels add risk?
Yes. Each added joint is a potential leak path: use the torque table, apply PTFE tape with 2-3 wraps, and confirm the assembly stays dry under working pressure.
How do I order custom lengths or ask about an application?
IsoHiTech Lubrication Systems was founded in 2023, engineering since 2006. Send thread sizes, lengths, materials, and quantities to inquiry@isohitech.com, or use the contact page.
