Abrasive Cloth: Top 10 Frequently Asked Questions — Answers Procurement and Operators Most Want to Know

Foreword:

In our daily sales and technical support work, we have found that customers’ questions about abrasive cloth are highly concentrated. Rather than having every new customer ask the same questions repeatedly, we have prepared a clear Q&A list. Whether you are responsible for procurement, warehouse management, or workshop grinding operations, the following 10 questions may be exactly what you are looking for.

Question 1: What do “P40” and “P120” on abrasive cloth mean? Does a larger number mean a finer grit?

Answer: Yes. The number after “P” follows the FEPA grit classification system. The smaller the number, the coarser the abrasive grains; the larger the number, the finer the grains.

• • P24～P60：Rough grinding, used for quickly removing oxide scale, weld seams, sprues, and risers.

• • P80～P120：Semi-finish grinding, used to remove marks left by rough grinding.

• • P150～P240：Fine grinding, used to obtain a uniform and delicate surface, often for brushing or pre-paint surface preparation.

• • P320及以上：Very fine polishing; this range is less common for abrasive cloth and is more often used for sandpaper.

Note: Fine-grit abrasive cloth should not be used to replace rough grinding directly. Otherwise, it may clog and heat up quickly, potentially scratching the workpiece instead.

Question 2: Why does abrasive cloth stop cutting after only a few minutes or turn black on the surface?

Answer: This is a typical loading problem, usually caused by one of the following reasons:

1. 1. The workpiece material is too soft, such as aluminum, copper, plastic, or paint. Chips adhere between abrasive grains and block the chip-holding space.
   2. The abrasive grit is too fine, leaving naturally smaller chip-holding space.
   3. Excessive pressure flattens abrasive grains and compacts the chips.
   4. Insufficient cooling or dust extraction causes heat buildup, which softens the material and makes it adhere to the abrasive surface.

Solutions:

• • For soft materials, use open-coat abrasive cloth with wider grain spacing or anti-clogging coated abrasive cloth.

• • Reduce grinding pressure and let the abrasive cloth “cut” on its own.

• • Use coolant or improve dust extraction efficiency.

• • If the problem persists, try using one coarser grit size.

Question 3: Can abrasive cloth be used with water or oil?

Answer: It depends on the backing material and bonding agent.

• • Ordinary paper backing or X-weight cloth backing: Not water resistant. It may delaminate, swell, or tear when exposed to water, and should only be used for dry grinding.

• • Y-weight waterproof cloth backing with resin bond: Can be used with water, oil, or emulsion, and is suitable for wet grinding or stainless-steel polishing.

How to identify: Check the product label or ask the supplier whether the product is marked “Waterproof” or “water-resistant.” If you are unsure, do not add water yourself, as this may cause the abrasive cloth to fail.

Question 4: What can be done if the edges of abrasive cloth tear or crack easily?

Answer: Common causes of edge tearing include:

1. 1. The abrasive cloth is too narrow, causing the edges to be suspended and bear stress.
   2. The workpiece has sharp edges or corners that continuously cut into the abrasive cloth edges.
   3. The backing strength is insufficient, such as using light J-weight cloth for heavy grinding.

Solutions:

• • Switch to X-weight or Y-weight heavy cloth backing, which has higher tear resistance.

• • Cut the abrasive cloth with rounded corners or use edge-reinforced products.。

• • During grinding, avoid placing the abrasive cloth edge directly against sharp workpiece corners; adjust the grinding angle accordingly.

Question 5: How should abrasive cloth be stored, and how long can it be kept?

Answer: Abrasive cloth is a resin-based composite material. It should be protected from moisture, direct sunlight, and compression.

• • Ideal environment: Temperature of 15–35°C, relative humidity of 40%–60%, away from light, well ventilated, and free from acidic or alkaline gases.

• • Storage method: Store flat or hang vertically, and avoid placing heavy objects on top. Rolls of abrasive cloth should be stored upright to prevent deformation.

• • Shelf life: When properly stored, resin-bonded abrasive cloth can be kept for 18–24 months. After more than two years, abrasive grains may fall off, the backing may become brittle, and bonding strength may decline.
    Recommendation: Follow first-in, first-out inventory management and check stock every quarter.

Question 6: Why does the same abrasive cloth last longer for some users than for others?

Answer: In addition to product quality, operating habits have a major impact on service life.

• • Pressure: Pressing harder does not make grinding faster. Instead, it accelerates abrasive grain fracture or clogging. The correct approach is to maintain a pressure of 2–5 kg and allow the abrasive cloth to cut properly.

• • Speed: Excessive linear speed, such as an angle grinder operating beyond the designed speed range of the abrasive cloth, can burn the bonding agent.

• •  Angle: Abrasive cloth should maintain a contact angle of 15–30 degrees. Flat pressing may lead to heat accumulation.

• • Workpiece material: The same abrasive cloth usually has a 30%–50% shorter service life when grinding stainless steel than when grinding carbon steel, because stainless steel has poor thermal conductivity and tends to adhere to abrasives.

Question 7: Should I choose cloth backing or paper backing? Which is more durable?

Answer: There is no absolute better or worse option. The choice depends on the working conditions.

In short: choose cloth backing for heavy-duty applications, paper backing for fine polishing, and waterproof cloth for wet grinding.

Question 8: Can abrasive cloth be reused, for example using cloth that has ground iron to grind aluminum?

Answer: It is not recommended.

• • Abrasive cloth used on iron may retain iron filings on the surface. If it is then used on aluminum, the iron filings may become embedded in the soft aluminum surface, causing electrochemical corrosion or surface blackening.

• • Abrasive cloth used on stainless steel may carry hard particles, which can leave deep scratches when used on softer materials.
    Correct practice: Use dedicated abrasive cloth for different materials whenever possible. If the abrasive cloth has only been lightly used and its surface is clean, it may be downgraded for rough grinding in less demanding processes, but it should not be used across significantly different material categories.

Question 9: How can I quickly judge the quality of abrasive cloth instead of just looking at price?

Answer: You can quickly assess quality through “look, touch, fold, and grind.”

• • Look: The abrasive grain coating should be even, with no blank areas or excessive buildup. The grain orientation should be consistent, as with electrostatic coating.

• • Touch: The surface should feel sharp, with no dull abrasive grains.

• • Fold: Fold the abrasive cloth 180 degrees. High-quality cloth backing should show no cracks or delamination.

• • Grind: Under the same conditions, grind a standard test piece and compare the grinding ratio, calculated as material removed from the workpiece divided by abrasive cloth weight loss.

More objective indicators: Ask suppliers to provide grinding rate (g/min) and grinding ratio data. This is more scientific than simply asking “How long can it last?”

Question 10: What is your minimum order quantity (MOQ)? Can I get free samples?

Answer：

• • Abrasive cloth rolls in regular grits (P40–P240): Orders are usually placed by the full roll, but A4-size sample sheets can be provided for testing free of charge, with shipping paid by the customer.

• • Non-standard widths or special abrasives: MOQ needs to be discussed, generally above 100 square meters.

• • Finished abrasive cloth pieces, such as discs or strips: Small quantities can be ordered for machine trials.

Recommendation: Contact our sales or technical team and tell us your workpiece material, grinding equipment, and target surface roughness. We will recommend the most suitable model and send samples for testing.

These 10 questions cover the key concerns related to abrasive cloth selection, use, and storage. If you have any other questions, please leave a message below or contact our technical engineers directly. We will continue to update this Q&A database.

Contact numbers: +86-757-2563 8000, +86-757-2563 6222