Felt

Felt is a compressed textile rather than a filament: wool, part-wool or synthetic fibres consolidated into sheet and then cut into wheels, pads, strips and shaped inserts. It works by area contact, so it is specified by density and thickness, not by diameter and trim.

Felt is used in custom cleaning brushes for controlled polishing, wiping, liquid transfer and sealing where a continuous compliant surface is preferred.

Where a project stalls on material choice, the comparison is normally against Wool, Microfiber and Cotton Yarn, and it turns on working temperature.

Compare Felt with Wool, microfiber, cotton yarn, nonwoven abrasive. Change material when wet stiffness, temperature, chemical resistance, conductivity, particle shedding, or surface marking becomes the limiting factor.

Felt covers a broad range, from a soft conformable pad to a dense firm polishing wheel; density and thickness are the figures that get stated. Contact pressure here comes from felt density and thickness together with how hard the wheel or pad is loaded. A soft thick felt conforms and polishes; a hard dense felt holds its edge and concentrates pressure on a small area. There is no trim length to specify.

The published material figures, set against the grades it competes with. The finished brush is rated from the whole assembly: face, backing and adhesive each have their own limit.

The part people get wrong: the number that decides scrubbing pressure is diameter over trim length, not the grade name. Two brushes in this material can behave nothing alike.

Felt is a compressed sheet rather than a filament, so it has no polymer absorption figure — what it holds is set by density and thickness.

Absorbent porous structure for wiping, washing, drying and liquid transfer.

What this means for your application: water changes the working diameter and the spring rate together, so wet performance has to be checked rather than assumed from a dry trial.

A practical check: soak a sample for an hour and re-measure the trim. If it has moved enough to change the contact band, the grade is wrong for the duty.

Ambient to 120°C.

Where it stops working: A face that stays compressed after the load comes off means the answer is a different compound or foam grade, not more thickness.

The usable limit also moves with thickness, density and how hard the face is pressed. A thick low-density pad under light load tolerates more than a thin dense one under heavy pressure.

Compatible with water and mild detergent; solvent and oxidizer resistance follows the fiber, foam and binder chemistry.

The same cleaner can be harmless or destructive depending on how strong it is, how hot it runs and how long it sits. Quote the concentration and the dwell time, not just the product name.

Before you commit to a quantity: Give the felt density, the sheet thickness, and the cut shape. Then say whether it runs wet, at what temperature, and what cleaner it meets.

Felt is a compressed textile supplied in sheet 3–300 mm thick and cut into wheels, pads, strips and shaped inserts. Density and thickness are the two figures: density decides whether the face conforms or holds an edge, thickness decides how much of that is left once it has worn down.

A soft thick felt conforms and polishes; a hard dense felt holds its edge and concentrates pressure on a small area. Say which of the two the job needs and the density follows from it.

Finishing available on this material: cutting, perforation and composite coating.

Controlled polishing, wiping, liquid transfer and sealing where a continuous compliant surface is preferred.

Brush types built with this fill:

• Custom Strip Seal Brushes

If the sample comes back rejected: Unspecified felt density or fiber content produces unpredictable pressure, absorption, wear and chemical response.

A usable specification carries the construction, the thickness and density or Shore figure, the cut shape and backing, and the service conditions: wet or dry, temperature, and what the cleaner actually is.

The mistakes that most often send a sample back:

• Selecting Felt from the material name alone without setting thickness, density or Shore hardness, and the cut shape
• Using dry stiffness to predict wet behavior without checking moisture absorption or liquid exposure
• Ignoring trapped abrasive particles, chemical concentration, temperature, or contact motion when assessing surface risk

Reference standards behind the figures on this page: ISO 139; ISO 5079; ISO 20743.

Source: SAE International — SAE J314 — wool and part-wool felts. Felt is specified by density and thickness rather than by fibre alone, and J314 is the grading system most industrial felt is bought against. Density is what decides whether a felt wipes, polishes or seals.