Gasket material

Cork-Rubber Gasket Material

Cork-rubber is granulated cork bound in an elastomer; the cited maker uses nitrile, nitrile/SBR and neoprene/nitrile binders. It is sold for oil and fuel joints at low pressure, and that maker offers grades for transformers and switchgear. We cut it to your drawing on the waterjet.

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Family: Cork granules in an elastomer binder
Temperature: 110 C (230 F) maximum in fluids; minimum -30 C (-22 F) at 3 mm and thicker, -20 C (-4 F) below 3 mm
Thickness: 0.8 mm to 13 mm (about 1/32 in to 1/2 in)
Formats: Sheets 1.2 x 1.0 m and 1.2 x 1.2 m
Designations: ASTM F104 (F224000M2, F225000M2); MIL-C-6183 / SAE AMS-C-6183
Product: Sheet gaskets waterjet-cut to your drawing in Orange, California

Figures are the cited maker or standards values; the sheet datasheet and your application govern the final choice.

Every common gasket sheet material is quick for us to source, and we cut it to your print on our waterjet. The other sheet materials are on the waterjet-cut gaskets page.

What cork-rubber seals

Cork-rubber is granulated cork bound in an elastomer: on the cited Nebar™ sheet the cork is nitrile-bonded below 3 mm and bonded with a neoprene/nitrile blend at 3 mm and above [S2]. Its maker rates it for fluids to 110 C at a recommended system pressure of 0.5 MPa, reports its swell in ASTM oils, fuel and transformer oil, and offers grades for transformers and switchgear [S2]. The MIL-C-6183 grades are specified for gaskets that need aromatic fuel and oil resistance [S1].

Above the maker's recommended 0.5 MPa system pressure or its 110 C fluid ceiling [S2], compressed fiber or solid rubber sheet is the usual choice.

Reading the callouts

ASTM F104 is the classification for nonmetallic gasket sheet, cork compositions included; rubber compounds fall under ASTM D2000 instead [S3]. The Nebar sheet carries the F104 line callout F224000M2 below 3 mm and F225000M2 at 3 mm and above [S2]. MIL-C-6183 has been superseded by SAE AMS-C-6183 [S1]. Put the full callout on the drawing and the sheet is matched to it.

Specifications

Cork-Rubber specifications

Values as published by the cited sources; [Sn] refers to the source list below
Property	Value (in / mm, C / F as stated)	Source
Composition	Cork granules bonded in synthetic rubber (the MIL-C-6183 scope); on the Nebar sheet, nitrile/SBR below 3 mm (predominantly nitrile-bonded) and a neoprene/nitrile blend at 3 mm and above	[S1, S2]
Hardness	65 to 85 below 3 mm; 65 to 80 at 3 mm and above	[S2]
Temperature, maximum in fluids	110 C (230 F)	[S2]
Temperature, minimum	-20 C (-4 F) below 3 mm; -30 C (-22 F) at 3 mm and above	[S2]
Pressure	0.5 MPa (5 bar, 73 psi), the maximum the Nebar datasheet recommends	[S2]
Thickness	0.8 mm to 13 mm on the Nebar sheet	[S2]
Formats	Sheets 1.2 x 1.0 m at 2.5 mm; 1.2 x 1.2 m at 3 mm and above	[S2]
Designations	ASTM F104 line callout F224000M2 below 3 mm and F225000M2 at 3 mm and above; MIL-C-6183 (superseded by SAE AMS-C-6183) for aromatic fuel and oil resistant gaskets	[S2, S1, S3]

How we cut it

Gaskets are waterjet-cut to your drawing in Orange, California. Send a DXF, DWG or PDF with the thickness, the material or the specification callout, and the quantity. There is no die to build, so a single prototype and a repeat run go through the same setup, and a revision needs only a new file. The sheet comes from the sheet makers we buy from, to the callout on your print; the cutting is ours.

Where Cork-Rubber is used, and the usual alternatives

The print or the sheet datasheet governs; these are the sheets usually specified instead:

Buna-N solid sheet: when the flange is machined flat and carries a bolted load with pressure behind it.
Compressed non-asbestos fiber: when the joint runs hotter than 110 C or sees more pressure.
Cellulose fiber: when a thin paper-type gasket does the job in oil or water.
Closed-cell sponge: when the lid seals against weather rather than oil.

Frequently asked

Is cork-rubber the same as cork-nitrile?

Cork-nitrile is cork-rubber with a nitrile binder. The cited maker's grades use nitrile, nitrile/SBR and neoprene/nitrile binders. Name the binder or the callout on the print.

What does MIL-C-6183 cover?

Cork-and-rubber composition sheet: cork granules held in vulcanized synthetic rubber, made for gaskets that meet aromatic fuels and oils. The military document is superseded by SAE AMS-C-6183, so new prints usually name the AMS version.

Can cork-rubber take hot water or steam?

Not above the 110 C fluid ceiling on the cited sheet. Hot water and steam joints usually take EPDM or compressed fiber sheet.

Which thickness should I ask for?

The one on the drawing. The cited Nebar sheet runs from 0.8 mm to 13 mm. Thicker sheet conforms to rougher faces but needs more bolt load to hold.

Sources

[S1] MIL-C-6183, Cork and Rubber Composition Sheet, for Aromatic Fuel and Oil Resistant Gaskets (S/S by SAE-AMS-C-6183), DLA ASSIST document record (revision B, 1981; Notice 1, cancellation, 1998), https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=5894, accessed 2026-10-13.
[S2] Nebar Brown datasheet, James Walker, BP4931 1122/PDF, Issue 1 (2022) (linked from https://www.jameswalker.biz/en/products/64-nebar-reg-grey), https://jameswalker.canto.global/direct/document/ha943k3jsp37pfo8sd2818br1g/U5Cc5w0lZSg0MCxCLyjSYO0g0Ss/original?content-type=application%2Fpdf&name=Nebar+Brown+datasheet.pdf, accessed 2026-10-13.
[S3] ASTM F104-11(2020), Standard Classification System for Nonmetallic Gasket Materials (public scope), https://store.astm.org/f0104-11r20.html, accessed 2026-09-28.

Nebar is a trademark of its owner. No affiliation or endorsement is implied.

Related guides

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Send the Cork-Rubber gasket drawing and the quantity

Upload a DXF, DWG or PDF of the gasket with the quote request, or a photo of the part with a ruler if no drawing exists. Add the sheet thickness, the durometer or grade, the quantity and whether adhesive backing is wanted. Gaskets are cut in our own shop in Orange, California; a Conquest representative replies. Quotes answered within one business day. A person answers (714) 632-9830, Pacific business hours.

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Last updated October 13, 2026