How to use flap disks safely and efficiently

July 11, 2023
By Walter Surface Technologies for the Blue Print

Working angle and pressure

Operate the flap disc at an angle between 2° and 15° for type 27 or 15° and 25° for type 29.
Do not exceed those angles to ensure an efficient and safe application.
Apply the optimal pressure by letting the rotational speed of the flap disc do the work.
Applying excessive pressure that bends the outer edge of the flap disc leads to premature wear and decreased tool life.

Proper operational speed

For optimal performance, move the flap disc along the surface slowly and steadily allowing the rotation of the flap disc to do the work.

Do not move the flap disc too quickly, nor aggressively back and forth. This will decrease its performance and provide a rougher surface finish.
Faster does not equal better when it comes to flap discs.

Proper trimming

Incorrect trimming can damage the flap disc. Some rules of thumb are:

Never trim at a 90°angle since this increases the risk of kickback.
Trim on secure sharp edges only.
Gently guide the backing of the flap disc towards the cutting edge.
Slightly angle your grinder between 15 and 25 degrees and, once the adhesive begins to appear, lower your angle, and stop trimming.
Unveil ¼” (6 mm) of new overhang at a time.
DO NOT trim the backing more than the recommended number of times as it will damage the structural integrity of the backing.

Caution! To avoid for risk of accident!

Avoid simultaneous contact at several grinding points due to risk of kickback. The flap disc could stop rotating if stuck, which may result in breakage of the flap disc.

DO NOT use the flap disc inside of square tubing.
DO NOT hit the flap disc against a sharp edge.
Avoid intense impact on the flap disc’s backing.

DO NOT grind into narrow workpieces. The flap disc can be drawn in, which can lead to sudden wheel stop and wheel breakage.

When using flap discs, always wear PPE, particularly, heavy-duty gloves, long sleeves, and eye protection, like safety glasses, goggles, or face shields.

Proper mounting

(1) Backing Flange (2) Clamping Nut (3) Integrated Backing Flange (5) Backing Flange (6) AVOID: Clamping Nut Inserted Upside Down

Situation 1: Needs a backing flange with a clamping nut. Note: The long face needs to sit on the disc (avoid situation 3).
Situation 2: Integrated backing flange with clamping nut. Note: In rare cases, the power tool includes this backing flange.
AVOID Situation 3: don’t forget to add the back flange because the backing pad of the flap disc can rub on the head of the power tool and lower performance. Note: The number 6 indicates a clamping nut inserted upside down which leads to excessive pressure around the hole, increasing risk of breakage. The long face should be in contact with the disc.
Situation 4: Needs a backing flange ONLY.

Extra safety tip

Take comfort and vibration into account when using flap discs, especially if used regularly and for long periods of time. Worker fatigue increases the risk of accidents and long-term exposure to vibration can lead to health issues down the road.

Avoid standard fiberglass flap discs as they don’t absorb vibration, but instead pass it on to the worker.
Nylon is a better alternative to fiberglass but still transfers some vibration to the worker.

Content originally from Walter Surface Technologies. Reused here with permission.

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