Industrial Felt Glossary

Every term you'll meet while spec'ing felt — defined plainly by a manufacturer since 1970.

Air Permeability: The rate at which air passes through felt under a defined pressure drop, measured in cm/sq.ft. or m³/m²/s. Falls predictably as density rises — F-1 felt is ~5–10 cm/sq.ft. while F-55 soft felt is 75–200.
Aramid (Nomex® / Kevlar®): High-temperature synthetic fibre used in blended felt for continuous service to 250 °C. Required for aerospace, fire-rated automotive and industrial filtration applications.
ASTM D461: American test method for wool and part-wool felt. Defines testing procedures for density, tensile strength, oil absorption and other properties. Classes A (Hard) through D (Soft).
Batt: The loose, fluffy layer of carded fibres laid down before felting or needle-punching. Multiple batts are layered to build target density.
Bob: Small mandrel-mounted polishing wheel, typically 10–50 mm diameter. Bobs are turned into shaped profiles (taper-head, conical-head, bullet, bell-head, knife-edge) for getting into tight features on jewellery, dental work and machined parts.
BSI / BS 2471: British Standards Institution specification for industrial wool felt. Largely equivalent to SAE J314 with minor differences in grade nomenclature.
Capillary (Oil Wicking) Height: The height to which felt can draw oil vertically against gravity. Higher density = higher capillary height. Critical for lubrication-wick design (oil reservoirs, transformer oil-wicks, journal-bearing wicks).
Carding: Mechanical separation and alignment of wool fibres before felting. The carded web's orientation determines the dimensional stability and feel of the finished felt.
CBR Puncture Resistance: Geotextile-specific test (EN ISO 12236) measuring how much force is needed to push a 50 mm CBR plunger through the fabric. Spec'd for road sub-base separation.
Coloured Felt: Pressed wool felt dyed in fast colours, available in plain (solid) and mélange (heathered) effects. Premier Felt offers any Pantone or RAL colour match on order.
Compressibility: Percentage thickness loss under load. Soft felts (F-50–F-55) are highly compressible; extra-hard felts (F-1–F-5) are nearly incompressible. Inversely related to density.
Density: Mass per unit volume, measured in g/cm³ for pressed felt. The single most important spec — it determines hardness, oil absorption, air permeability, tensile strength and acoustic behaviour. Industrial range: 0.15 to 0.75 g/cm³.
Die Cutting: Manufacturing process where steel-rule or clicker dies stamp custom shapes (washers, gaskets, rings, wicks) from felt sheet. Premier Felt's in-house die shop produces 1,000s of custom geometries to customer drawings.
DIN 61200: German Industrial Standard for wool felt. Defines grades F1 through F11, broadly corresponding to SAE J314 F-1 through F-55.
ETP (Effluent Treatment Plant): On-site facility that treats process water before discharge. Premier Felt's Bikaner factory operates a full ETP to meet Rajasthan Pollution Control Board norms — water from dyeing and wet-felting is recycled or discharged within statutory limits.
Felting: The natural process by which wool fibres entangle and lock together under moisture, heat and mechanical agitation. The scales along wool fibres open in one direction and lock into adjacent fibres, progressively densifying the mat.
FR (Fire-Retardant) Treatment: Chemical finish applied to felt to raise its fire-resistance rating beyond wool's natural self-extinguishing baseline. Common targets: FMVSS 302 (automotive), UL 94 V-0 (electrical), EN 45545 (rail).
Geotextile: Permeable needle-punch fabric used in civil-engineering applications (road sub-base separation, drainage, erosion control, retaining-wall reinforcement). Premier Felt's geotextiles are polypropylene or polyester needle-punch, 150–800 GSM, up to 6 m wide.
GOTS: Global Organic Textile Standard. Premier Felt is GOTS-certified for organic wool processing — covering raw-material origin, chemistry, social compliance and traceability through to finished felt.
GSM (Grams per Square Metre): Mass per unit area, the principal spec unit for needle-punch and geotextile felt (1.5 oz/yd² ≈ 50 GSM). Range: 100 GSM (thin needle-punch) to 1,200 GSM (heavy industrial geotextile).
Hardness Class: SAE/DIN convention for grouping felt by density: Extra Hard (0.45–0.75 g/cm³), Hard (0.31–0.44), Medium Hard (0.24–0.30), Soft (0.15–0.23).
ISO 9001:2015: International Quality Management System standard. Premier Felt holds active ISO 9001:2015 certification covering raw-material inspection, process control, finished-goods QC and customer-issue handling.
IS 282: Indian Standard for wool felt. The Indian equivalent of SAE J314, used in defence, railway and government tenders within India.
Knife-Edge Disc: A felt polishing wheel ground to a sharp circumferential edge for entering narrow grooves — jewellery channel-setting, watch-bracelet links, automotive trim grooves.
Lubrication Wick: A pressed-felt strip or ring saturated with oil that meters oil onto a moving part (journal bearing, slide-way, chain). Wool's high capillary height makes it the standard wick material.
Mandrel: The metal shaft that a polishing bob is mounted on (typically 3 mm, 6 mm or ¼" shaft). "Mandrel-mounted" felt bobs come pre-mounted; "unmounted" bobs are bare felt with an axial hole.
Mélange: Heathered dye effect produced by blending coloured fibres before felting (vs surface-dyeing the finished sheet). Gives a richer, fade-resistant colour favoured for craft and design applications.
Needle-Punch Felt: Non-woven fabric made by mechanically entangling fibres using thousands of barbed needles. Suitable for synthetic fibres (polyester, polypropylene) and wool blends. Lighter, more porous and cheaper than pressed felt; better for filtration, insulation, geotextiles and equestrian use.
NRC (Noise Reduction Coefficient): A single-figure rating of sound absorption averaged across 250, 500, 1000 and 2000 Hz octave bands. 25 mm Premier Felt: 0.45 (Extra Hard) to 0.64 (Soft) — soft felt absorbs more sound.
Oil Absorption: Maximum oil mass a felt can hold relative to its own mass (>150% by weight typical). The basis of felt's use as oil-wicking lubricator and oil-cleanup material.
Pressed Felt (Pressed Wool Felt): Felt made by the traditional wet-felting / fulling process — moisture + heat + mechanical pressure compresses carded wool batts into a tight, isotropic mat. The strongest, densest, most dimensionally stable felt.
Resin Bonding: Optional secondary process where felt is impregnated with a thermosetting resin to raise stiffness, oil resistance or compressive strength. Used for hard machine bushings and structural gaskets.
SAE J314: Society of Automotive Engineers specification for wool felt grades F-1 through F-55. The de-facto global classification — see our complete SAE grade chart.
Saddle Soaping: Traditional finishing process for equestrian felt: a mild fatty-acid soap is rubbed into the wool to lubricate fibres, soften the hand, and improve moisture wicking.
Square Edge Wheel: Cylindrical felt polishing wheel with a 90° edge profile, as distinct from taper-head, bell-head or knife-edge shapes.
Tensile Strength: Force per unit area required to tear felt in straight pull, kPa or N/m². Range: 1,500 kPa (Soft) to 6,000 kPa (Extra Hard).
VOC / FOG: Volatile Organic Compound emissions / windscreen-fogging mass — interior automotive specifications measured per VDA 278 and VDA 277. Premier Felt's automotive-grade felts meet low-VOC and low-FOG OEM specs.
Wicking: The capillary movement of liquid through felt's fibre network. Wool's hollow fibre structure makes it the natural choice for lubrication wicks, oil reservoirs and moisture-management equestrian felts.
Wool Content: Percentage of the felt's fibre that is wool, by mass. SAE grades F-1 to F-13 require 100% wool; lower grades permit synthetic blends. Higher wool % = better felting, longer service life, biodegradable end-of-life.

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