Cork, Leather and Felt
Cork, leather and wool felt are the compliant natural materials: sheet goods that are cut, punched, skived and stitched rather than machined, chosen for how they yield, seal, wipe and hold oil rather than for strength. Natural cork is a closed-cell bark at 0.12–0.24 g/cm³ that compresses by half and recovers, insulates at about 0.04 W/m·K and barely bulges sideways when squeezed; cork-rubber composition binds cork granules in nitrile or neoprene into gasket sheet for oil, fuel and vibration; leather is collagen fiber tanned with vegetable tannins (firm, mouldable, tool-friendly) or chromium salts (soft, supple, heat- and water-resistant); SAE J314 wool felt in F-1 hard to F-3 medium grades and FA wool-synthetic blends is the standard wiper, wick, seal and polishing material. All of them creep under sustained load, take up moisture and live below about 100–120 °C.
Popular cork, leather and felt grades
Compare in the explorer| Grade | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|
| Natural Cork | — | 1 | 0.16 | Excellent | — | Low-pressure gaskets, pads, stoppers, thermal breaks |
| Cork Composition (Cork-Rubber) | — | 2 | 0.75 | Excellent | — | Oil-resistant gaskets and anti-vibration mounts |
| Vegetable-Tanned Leather | — | 22 | 0.92 | Good | — | Tooled, moulded and burnished straps, cases, seals |
| Chrome-Tanned Leather | — | 26 | 0.9 | Very good | — | Soft, water-resistant gloves, grips, upholstery |
| SAE F-1 Wool Felt | — | 3 | 0.32 | Excellent | — | Hard felt wipers, seals and polishing pads |
| SAE F-3 Wool Felt | — | 2 | 0.3 | Excellent | — | Medium felt wicks, dust seals and pads |
| SAE FA-1 Synthetic-Wool Blend Felt | — | 1 | 0.3 | Excellent | — | Low-cost padding and light seals |
Choose cork, leather and felt for
Oil-pan, cover and low-pressure flange gaskets; anti-vibration and levelling pads under equipment; wipers, wicks and oil-retaining seals on shafts and ways; polishing, burnishing and buffing pads; straps, grips, holsters, cases and wear-facing trim; stops, bumpers and cushions where a polymer would be too hard or too slick; and prototype soft goods in small quantities cut from sheet without tooling.
Look elsewhere when
The seal sees pressure above a few bar or must hold a set compression for years (an NBR, EPDM or Cast Silicone gasket), the part runs above about 100–120 °C (silicone, PTFE or a graphite gasket), oil and fuel contact is continuous on plain cork or felt (Cork Composition (Cork-Rubber) or a nitrile sheet), size must hold across humidity (leather and felt swell and stretch — use a polymer), the wear surface is dry and fast (UHMW-PE or PTFE), or the product must be animal-free (a synthetic microfiber or TPU-coated fabric).
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Cork, leather and felt by application
- Gaskets and seals
- Cork Composition (Cork-Rubber) for oil pans, covers and flanges to a few bar; Natural Cork for dry, low-pressure and thermal-break joints; SAE F-1 Wool Felt or SAE F-3 Wool Felt for grease-retaining shaft seals and dust wipers on slideways.
- Vibration and levelling pads
- Cork Composition (Cork-Rubber) sheet 3–12 mm under machines, compressors and instruments; Natural Cork where the load is light and the pad must not creep sideways; SAE F-1 Wool Felt as a firm damping layer.
- Straps, cases and grips
- Vegetable-Tanned Leather where the part is cut, tooled, edge-burnished and expected to hold shape; Chrome-Tanned Leather for soft, sweat- and water-resistant grips and linings; Split Leather and Bonded Leather Board for linings, insoles and backing.
- Wicks, wipers and polishing
- SAE F-3 Wool Felt oil wicks and pads, SAE F-1 Wool Felt polishing bobs and wipers, Rawhide mallet faces, and Vegetable-Tanned Leather strops and burnishing wheels.
Working with cork, leather and felt
- Cutting and machining
- All three are die-cut (clicking or steel-rule dies), knife-cut, laser-cut or waterjet-cut from sheet rather than milled. Laser cuts cork, felt and vegetable-tanned leather cleanly with a dark sealed edge; chrome-tanned leather lasers with more odour and a harder edge. Leather is skived to thickness and split; felt is sliced from block to 1.5–25 mm; cork sheet and rod turn and sand with woodworking tools. Tolerance of ±0.3–0.5 mm on a die-cut part is realistic; thickness varies about ±10 % across a sheet.
- Joining and fastening
- Contact adhesive and polyurethane glue bond cork and cork-rubber to metal, and pressure-sensitive adhesive backing is standard for gaskets and pads. Leather is stitched with waxed thread, riveted, laced or bonded with contact cement; edges are skived before folding. Felt is bonded with contact or hot-melt adhesive, needle-punched to a backing or held by its own compression in a groove. Nothing here welds, and screws pull through without a washer or a metal edge.
- Finishing
- Vegetable-tanned leather is dyed, oiled, waxed, embossed, stamped and edge-burnished; chrome-tanned leather arrives finished from the tannery and takes little more than a protectant. Cork is used raw, sanded, waxed or varnished; cork-rubber is left as sheet. Felt is used as cut and can be dyed or laminated to a backing. Hot-foil stamping takes on leather; laser engraving takes on all three.
- Movement and moisture
- Leather stretches 5–15 % under load, absorbs water, and vegetable-tanned leather shrinks and hardens if dried wet — wet-form it deliberately, never above 60 °C. Wool felt absorbs up to a third of its weight in moisture, compresses permanently by 10–20 % under sustained load and can mildew if kept damp. Cork is the most stable of the three — under 1 % dimensional change across normal humidity — but it dries and crumbles above 120 °C and in prolonged UV. Store all three flat, dry and out of sunlight.
Other natural material series
Cork, Leather and Felt — frequently asked
What is cork, leather and felt?
Cork, leather and wool felt are the compliant natural materials: sheet goods that are cut, punched, skived and stitched rather than machined, chosen for how they yield, seal, wipe and hold oil rather than for strength. Natural cork is a closed-cell bark at 0.12–0.24 g/cm³ that compresses by half and recovers, insulates at about 0.04 W/m·K and barely bulges sideways when squeezed; cork-rubber composition binds cork granules in nitrile or neoprene into gasket sheet for oil, fuel and vibration; leather is collagen fiber tanned with vegetable tannins (firm, mouldable, tool-friendly) or chromium salts (soft, supple, heat- and water-resistant); SAE J314 wool felt in F-1 hard to F-3 medium grades and FA wool-synthetic blends is the standard wiper, wick, seal and polishing material. All of them creep under sustained load, take up moisture and live below about 100–120 °C.
Which grade of cork, leather and felt should I use?
Natural Cork for low-pressure gaskets, anti-vibration pads, stoppers and thermal breaks where a closed-cell, chemically inert, near-incompressible sheet is wanted; Cork Composition (Cork-Rubber) for engine, gearbox and cover gaskets, mounting pads and anti-skid feet, because the rubber binder adds oil resistance, strength and a controlled compressibility plain cork lacks. Vegetable-Tanned Leather for anything that is tooled, wet-formed, burnished or must hold a shape — sheaths, straps, cases, seals for vintage equipment, strops and polishing wheels; Chrome-Tanned Leather for soft, supple parts that see water and wear — gloves, upholstery, grips and garments; Split Leather as the lower-cost suede-faced layer for linings and pads; Bonded Leather Board for insoles, heel stacks and backing; Rawhide for mallet heads, drum heads and lacing that must be rock-hard when dry. SAE F-1 Wool Felt for wipers, seals, dampers and polishing pads that must resist wear; SAE F-3 Wool Felt for oil wicks, pads and dust seals where softness and absorbency matter; SAE FA-1 Synthetic-Wool Blend Felt when cost matters more than durability in padding and light seals.
Which grade of cork, leather and felt is easiest to machine?
Split Leather (machinability excellent, 90/100), then Bonded Leather Board (85/100).
Vegetable-tanned or chrome-tanned leather?
Vegetable-Tanned Leather is firm, dense and holds a shape: it tools, stamps, wet-moulds, burnishes and ages to a patina, which is why sheaths, belts, saddlery, strops and machine parts are made of it — but it stains and stiffens with water and shrinks if it dries wet. Chrome-Tanned Leather is soft, stretchy and stable, resists water and heat better (it survives near-boiling water where vegetable tan shrinks around 75 °C), takes bright colours and is the leather of gloves, upholstery and garments; it cannot be tooled or burnished. Structural or shaped parts: vegetable; soft, wearable, wet-service parts: chrome.
What do the SAE felt grades F-1, F-3 and FA-1 mean?
SAE J314 classifies pressed wool felt by density and wool content. F-1 is the hard, dense, all-wool grade for wipers, seals, polishing bobs and parts that must resist wear and hold their shape under a shaft; F-3 is a medium-density all-wool felt that stays softer and more absorbent — the choice for oil wicks, dust seals and cushioning pads; FA grades blend wool with synthetic fiber for lower cost and go into padding, light seals and sound damping where the wool properties are not critical. Specify the grade and thickness; sheet tolerance is about ±10 %.