Wednesday, November 30, 2022

How to choose a flap disc

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As we have already seen, flap discs have a number of advantages over conventional abrasive discs, as they offer two tasks in one (grinding and finishing) at reasonably high speeds and with more than acceptable quality. In addition, they produce practically no noise or vibrations, which translates into greater comfort for the user, increasing productivity.

Until a few years ago, a single disco flap to work all kinds of materials and pieces. However, today many specific models with different properties are offered, creating a great variety on the market. Because of this, it is not easy to make the right decision when choosing a disco flap according to our needs.

Stainless steel flap disc

However, the guidelines that we will provide in this article will help the future buyer to make a suitable purchase, saving time and money in the disco flap Not only will it be the best fit for the job, but it will also provide a long service life.

Fundamental parameters to consider

As precisely the performance of a disco flap is closely related to abrasive material, grain size, and backing, let’s start with these considerations.

In a previous article we already covered the most common types of abrasive material of the flap discs, as well as the recommended grain size according to the task to be carried out and the various supports. We are going to recall and summarize that information in these charts.

a) Abrasive material

Type of abrasive material Aluminum oxide Zirconium Silicium carbide Ceramic oxide
Recommended materials for use Metal Stainless steel and metal Masonry Stainless steel, ferrous and non-ferrous metals
Wood X
Plastic X
Ferrous metal XX XX XX
Nonferrous metals X X XX
Stainless steel XX XX
Masonry XX XX
XX = recommended X = acceptable

b) Abrasive grain size

Grain size 40-60 80-100 120 and above
Recommended Task Roughing, material removal General grinding, sanding Finish, very smooth and non-marking surfaces

c) Support plates

Material Advantages Disadvantages
Fiberglass
  • The most popular.
  • Extremely strong, durable and safe.
  • Create a strong bond with the adhesive.
  • Does not contaminate the work surface
  • To improve safety, it is recommended to mount the discs on the grinder using a mounting flange.
Plastic
  • Very used.
  • It can be trimmed to increase the use of abrasive material.
  • Available in a variety of colors.
  • The shaft hole thread can be an integral part of the bracket.
  • To improve safety, it is recommended to mount the discs on the grinder using a mounting flange.
  • It can contaminate the work surface.
  • It should be specially designed to increase surface contact for stronger adhesion or have the surface treated.
  • Not safe like fiberglass
  • It can deform at high temperatures.
  • Not recommended for very low temperatures.
Metal
  • Safer.
  • Metal backed flap discs provide the most aggressive grinding.
  • Support flange is not required.
  • More expensive than fiberglass or plastic.
  • You need a compatible adhesive.

Other considerations

a) Diameter and speed of the disc

One of the precautions that we must observe when working with abrasive discs in general and flap discs in particular, it is the relationship between the diameter and the maximum rotational speed for which the disc is designed.

The flap discs Most common ones come in two diameter sizes:

  • 4 ½ inches (115 mm)
  • 7 inch (180mm)

The larger the diameter, the lower the speed of rotation. To avoid disc breakage and personal accidents, we must always check that the speed of our angle grinder or sander (whether wired or wireless) is not higher than the speed marked on the disc. In the event that the speed of the disc is less than the speed of the tool, or if the speed is not specified, it is better not to use the disk.

Recognized manufacturers include these and other indications in their flap discs, as we see in the following figure.

Flap disc - indications

Flap disc – indications

b) Tips for choosing flap discs according to the material to be worked

If our record choice is for a single particular material, here are some additional guidelines to consider.

Flap discs for aluminum: Compared to other metals, aluminum has a lower melting temperature and melts easily. This causes the aluminum material to create a coating on the surface during grinding. disco flap, covering the grain and exposing only small pieces of aluminum. For roughing, use a T29 tapered wheel at a 15 degree angle to provide maximum surface contact. If we just need a surface cleaning or a smooth finish, then we will use a T27 flat disk parallel to the work area. For best results we must exert light and even pressure to optimize the grinding process and reduce load.

Flap discs for wood: They are similar to those designed for use on metal and offer excellent performance on wood. The most recommended abrasive material in this case is aluminum oxide, and we will mount the discs on our angle grinder just as we would with a common abrasive disc. To avoid deep marks on the surface of the wood, we must start with a coarse grain and then progress to the finer grains (100+) for a final finish. For sanding the wood we have to work with grain sizes of 120, 150, 180 and 220 in order to achieve a surface with the finish that any furniture presents.

Flap discs to remove paint: It is possible that we have a rusty metallic object that we want to extend its useful life or that our vehicle has sectors of old and / or peeling paint that we want to remove to give it a new appearance. The flap discsespecially those containing nonwoven abrasives and aluminum oxide are tools Ideal for removing paint and rust. Both one and the other, like the flap discs generally, they can offer roughing and finishing in one operation, while providing smooth and controlled roughing.

Flap discs for concrete: for aggressive removal of concrete material we will need flap discs silicon carbide, or diamond, which are one of the hardest abrasive materials. The use of these discs will allow us to work on concrete surfaces without the need to exert great pressure on them. They feature rigid supports and can also be used on other surfaces such as stone, granite, marble, iron, steel, stainless steel, copper, bronze, aluminum, welding, rust, masonry, plastic, wood, fiberglass, lacquer, paint, and ceramics .

Diamond flap discs

Diamond flap discs

Flap discs for welding: We can polish, clean and finish a weld bead without affecting the original metal, as well as surfaces, edges and edges of steel, cast iron in general, non-ferrous materials (copper, bronze, aluminum, titanium, plastic, wood, etc.) and remove rust, varnish and paint with a disco flap of zirconium oxide with grain size 80. Discs that have fiberglass supports have the advantage of not contaminating the work surface, which also makes them ideal for working on stainless steel.

c) Tips for using flap discs

To get the maximum benefit from our flap discsTo extend its useful life and work safely, without danger of injury to the operator or breakage of the disc, the grinder or the workpiece, it is necessary that we follow a series of highly recommended measures. Let’s make sure to put them into practice every time we use a disco flap.

i) What should we do
  • Before use: 1) carefully read the instructions for use that accompany the disco flap and the grinder / sander, and consult the manufacturers if you have any questions; 2) check the discs for damage to the blades or the support plate. If there is damage, we must discard the disc, and 3) perform a one minute test run of the disc in an enclosed area, eg a barrel, at operating speed.
  • Select a suitable disk for our application. The recommendations we provide in this article can help us do this.
  • Disconnect the grinder from the power source before changing a disco flap.
  • Use 4-inch and larger diameter wheels on angle grinders / sanders fitted with a guard.
  • Match the size of the disc to that of the grinder / sander (for example, a 7-inch disc for a 7-inch grinder / sander).
  • Check the speed of the machine with the safe operating speed set and marked on the disco flap. We should never exceed the rated speed of a disco flap.
  • Use appropriate personal protection, such as protection for the eyes and face, for the arms, apron, gloves, safety shoes, hearing protection, etc., duly approved. Wear a respirator when harmful materials are produced, such as sawdust, toxic metal particles, etc.
  • When necessary, use suitable clamping flanges supplied by the manufacturer of the grinder or grinder. disco flap. If our angle grinder / sander comes equipped with a side handle, we must use it for safety.
  • When working on small parts that can be projected during grinding or sanding, use a workpiece holding accessory.
  • Use the disco flap at the right angle. Type 27 blades should be used at a 0 ° -15 ° angle and Type 29 blades at a 15 ° -25 ° angle to the workpiece.
  • After use: store the disc in its original container, away from water or other fluids and in an environment at a temperature between 15ºC and 29ºC and a relative humidity between 40% and 50%.
ii) What should we NOT do?
  • Do not use the disc on pneumatic pistol grip sanders or any other tool inadequate.
  • Do not store the disc on concrete floors, near open windows, in direct sunlight, or near heat sources such as radiators or steam pipes.
  • Do not use discs that have been dropped or appear damaged in any way.
  • Do not exceed the maximum RPM marked on the disk.
  • Do not use a disco flap to make cuts.
  • Do not install the disc in a machine that is not in good working order.
  • Do not let the blade get stuck in the workpiece.
  • Do not let the disc become “loaded” with chips that we are removing from the workpiece.
  • Do not use a disco flap If we are not sure how to do it and / or we do not have adequate training in the use of the disk and the tool.

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