A hydraulic line that has to cross a tank wall, a frame plate or a manifold panel needs a sealed pass-through. The 6C metric bulkhead fitting does that job with two 24° cone light series ends, built to DIN 2353 and ISO 8434-1. This guide covers the size range, thread list, pressure ratings and the hole preparation needed before installation.
What Is a 6C Metric Bulkhead Fitting?
The 6C is a straight bulkhead union with metric male 24° cone ends on both sides. Both ends use the light series (L series) dimensions of DIN 2353. The body carries a longer threaded section and a hex so it can be clamped through a panel with a locknut.
Each end seals the same way as a standard metric compression fitting. The tube slides into the cone. A cutting ring bites into the tube wall when the nut is tightened. The metal-to-metal contact at the 24° cone makes the seal. No O-ring sits in the fluid path, so there is no elastomer to age out.
The Problem It Solves: Lines That Must Cross a Wall
Without a bulkhead fitting, a tube either stops on one side of the panel or runs through a bare hole. Both options fail in service:
A bare hole lets the tube chafe against sheet metal until the wall thins and the line bursts.
A hose routed around the panel adds two extra couplings and two extra leak points.
A fitting threaded into the panel wall itself puts all the bending load on the thread.
A bulkhead fitting removes all three problems. The body takes the clamping load. The tube enters and leaves through sealed cone connections. The number of couplings in the line stays unchanged.
Key Features of the 6C Panel-Mount Design
Two 24° cone ends. Light series geometry on both sides, so both tubes use the same cutting ring family.
Through-panel thread. The body thread is long enough for panels, frame plates and thin tank walls.
Hex for counter-holding. The installer holds the body with a spanner on one side and turns the locknut on the other. The body does not rotate while the cone is being seated.
Set delivery. Nuts and cutting rings ship with the body, matched to the correct series.
Machined body. The cone is cut on a CNC lathe, not cast. Cone finish controls weeping under pressure cycling.
6C Specifications and Materials
Item
Value
Standard
DIN 2353, ISO 8434-1 interface
Series
Light series (L)
Sealing form
24° cone with cutting ring
Body material
Carbon steel C45, cold drawn or hot rolled
Plating
Zn-Ni alloy, 8–12 μm, 240+ h salt spray (ASTM B117)
Optional material
Stainless steel 316L for marine or chemical duty
Temperature range
−40 °C to +120 °C (NBR), −40 °C to +150 °C (FKM)
Working pressure
315 bar up to 18 mm tube; 160 bar from 22 mm (static, 4:1 safety factor)
Panel hole values allow 1 mm clearance over the thread major diameter. Increase the clearance if the panel is painted, galvanised or if two fittings share a common mounting plate.
How to Mount a 6C Bulkhead Fitting Through a Panel
Check the panel. The surface must be flat where the locknut and washer seat. Reinforce thin plate with a backing plate.
Drill or punch the hole. Use the clearance in the size chart. Deburr both faces. A burr holds the washer off the surface and starts a leak path.
Fit the body. Slide the body through from the tank or machine side. Put the washer and locknut on from the outside.
Tighten the locknut. Hold the hex with a spanner so the body cannot turn. Snug the locknut, then give it a final quarter turn.
Prepare both tubes. Cut square, deburr inside and out, and slide the nut and cutting ring on with the cutting edge facing the tube end.
Seat the cone. Lubricate the cone and ring, hand-tighten the nut, mark it, then turn 1.5 turns for light series.
Pressure test. Bring the circuit to working pressure and check both sides of the panel for weeping before the machine goes back to work.
Where 6C Bulkhead Fittings Are Used
Hydraulic reservoirs. Return and suction lines entering through the tank wall.
Mobile equipment frames. Lines crossing from the engine bay to the boom or chassis.
Valve manifolds and power packs. Panel plates on compact hydraulic units.
Agricultural machinery. Tank and frame pass-throughs on tractors and harvesters.
Industrial machines. Presses and injection moulding units with safety guards between pump and tool.
Why Source Bulkhead Fittings from Ruihua Hardware
Ruihua Hardware machines DIN 2353 metric fittings as a core product family, so bulkhead bodies share tooling, plating and inspection routines with the rest of the metric range. That keeps material traceability simple on mixed orders.
C45 carbon steel as standard, with 316L stainless quoted against drawing.
Zn-Ni plating with 240-hour salt spray results available per batch.
Sets shipped complete — body, nuts and cutting rings from the same production lot.
Customised thread combinations and body lengths quoted from drawings or samples.
Frequently Asked Questions
What sizes does the 6C metric bulkhead fitting cover?
Tube outside diameters of 6, 8, 10, 12, 15, 18, 22, 28, 35 and 42 mm. Threads run from M12 x 1.5 to M52 x 2.
How large should the panel hole be?
Drill 1 mm larger than the thread major diameter. A burr left on the hole edge will hold the washer off the panel and cause a leak.
Can it be used on a hydraulic tank wall?
Yes. A bonded seal or O-ring under the locknut is recommended on painted or rough surfaces.
Is stainless steel available?
Yes, quoted against drawing. Standard production is C45 carbon steel with Zn-Ni plating passing 240 hours neutral salt spray per ASTM B117.
Does the fitting ship with nuts and cutting rings?
Yes. Ordering the complete set avoids mixing light and heavy series parts.
Get a quote for DIN 2353 bulkhead fittings. Send the tube size, thread combination, panel thickness and quantity. Ruihua Hardware cross-references existing part numbers and returns a quotation within 24 hours. Sample sets with mixed sizes are available for evaluation.
Lynn Liu is a Senior Foreign Trade Specialist at Ruihua Hardware with over 10 years of experience in hydraulic fittings export. She helps global buyers source reliable, cost-effective, and application-ready hydraulic connection solutions from China.
