6mm Compression Nut Fittings for Centralized Lubrication
These fittings connect 6 mm outside diameter tubing to pumps, dividers, and bearing points across a lubrication circuit. The nut draws the tube into a 24 degree cone seat, where a ferrule bites and seals. Threads only clamp the assembly together. This page describes the hardware by geometry and dimensions so you can match fittings to your tube runs and port threads.
How the 24 Degree Cone Seal Works
The seal forms at the 24 degree cone and the ferrule, not at the thread. As the nut advances, the ferrule is driven onto the cone, compressing the tube wall and creating a metal-to-metal or plastic-to-metal seal. The thread provides clamping force only. Never add sealant to the cone side, because it can prevent the ferrule from seating correctly and block the lubricant path.
Port sealing depends on the thread type. BSPP (G) ports seal on a bonded washer or a machined face. NPT ports seal on the taper, so sealant is applied to the thread.
Threads, Sizes and Tightening Guidance
Fittings are available with M10x1, M12x1.5, G1/8, G1/4, and NPT versions. Hex sizes are 12 and 14 across the nut, and 14, 17, and 19 across the body. The table below lists typical guidance, supplier reference values for tightening. Always confirm the final torque against your tube material and wall thickness.
| Thread | Typical tightening |
|---|---|
| M10x1 | 15-18 Nm |
| M12x1.5 | 20-25 Nm |
| G1/8 | 12-15 Nm |
| G1/4 | 25-30 Nm |
After the ferrule contacts the cone, turn the nut an additional 1.25-1.5 turns for steel tube, or 1-1.25 turns for nylon tube. Stop if the nut becomes difficult to turn, because over-tightening can crush the tube.
Material and Pressure Guide
Material choice follows the working pressure class and the environment. The table below lists typical working pressure classes for common materials. Use it as a guide when matching fittings to pump output and circuit layout.
| Material | Typical working pressure class |
|---|---|
| Zinc-plated steel (LL series) | 100 bar |
| Nylon | 80 bar |
| High-pressure steel | 250 bar |
| PA12 | 300 bar |
| Stainless 316 | 315 bar |
| Brass | 60 bar |
Steel suits general indoor duty. Stainless 316 is for washdown and corrosive sites. Brass works well for low-pressure gauge lines. Nylon and PA12 are useful where vibration and routing flexibility matter. For tubing selection, see the lubrication tubing and hose selection guide.
What Is Supplied
Each fitting includes a body, a ferrule, and a compression nut. Bodies are machined with the 24 degree cone seat and the requested port thread. Nuts are sized for 12 or 14 across flats, depending on the series. Bodies use 14, 17, or 19 across flats. Tube acceptance is 6 mm outside diameter with a tolerance of about 0.1 mm, and wall thickness from 0.5 to 1.5 mm.
For related hardware such as bulkhead adapters, plugs, and manifold studs, see lubrication accessories. If you are comparing connection styles, the guide on compression versus push-in lubrication fittings explains where each type performs best.
Assembling Tubing Correctly
Cut the tube square and deburr both the inside and outside edges. Slide the nut and ferrule onto the tube, then push the tube fully into the body until it bottoms on the shoulder. Hold the body with a wrench and tighten the nut by hand until the ferrule contacts the cone. Then apply the additional turns listed above. Avoid rotating the tube while tightening, because that can score the sealing surface.
For reuse, inspect the ferrule bite marks on the tube. If the marks are shallow or uneven, replace the ferrule and cut a fresh tube end. Brass fittings are available for low-pressure circuits; see metric brass lubrication fittings. For pump connections, review the grease pump range. To discuss your circuit and request a quotation, contact us for a quote.
Frequently Asked Questions
Which thread do I need on the equipment side?
Match the port thread on your pump, divider, or bearing point. Options include M10x1, M12x1.5, G1/8, G1/4, and NPT versions.
How tight should the nut be?
Follow the table values as a starting point, then add 1.25-1.5 turns for steel or 1-1.25 for nylon.
Does the fitting need thread sealant?
Only on NPT threads. Never seal the 24 degree cone side, where the ferrule must seat on clean metal.
Can I use nylon tubing?
Yes, in the 80 bar class. It uses fewer tightening turns than steel tube.
Which material for washdown areas?
Stainless 316, in the 315 bar class, suits washdown and corrosive sites.
Can fittings be reused?
Reuse is possible when the ferrule and cone are undamaged; inspect bite marks and replace worn rings.
How do I prepare the tube end?
Cut square, deburr, and bottom the tube on the shoulder. Do not rotate it while tightening.
Do you supply brass versions?
Yes, for low-pressure gauge lines; see the metric brass fittings page.
Where do I confirm a full size list?
Send your circuit details through the quotation request page and we will confirm the available threads, hex sizes, and materials.
Who supplies these fittings?
IsoHiTech Lubrication Systems, founded in 2023, engineering since 2006, builds and supports every unit. Email inquiry@isohitech.com for specifications and a quotation.
