Get the most out of your flap disc

PFERD

In the realm of surface conditioning tools, fabricators have many options available too them. In recent years and for a variety of reasons, the flap disc has become front and centre in the conversation for its many benefits.

Flaps discs are designed for right-angle grinders and provide both material removal and finishing operations. They also can simplify processes that require multiple tools and steps. However, not all fabricators know about the advantages of using these tools.

“Sometimes fabricators stick with what they know or follow how things have always been done,” said Steve Bell, Quebec territory sales manager for PFERD Canada, Mississauga, Ont. “Having a certain experience and familiarity with a tool can be beneficial, but it’s important to test out other options to see what works best. Trying out a flap disc often demonstrates immediate advantages for the operator and application.”

These advantages include productivity gains, economic benefits, and improved ergonomics.

Advances in welding technology have made it possible to deposit thinner welding beads, making flap discs a suitable choice for most surface preparation applications.

“Prior to the introduction of coated abrasive flap discs, metal surface preparation has usually required the use of bonded abrasive grinding wheels for the initial material removal, followed by finishing with coated abrasive resin fibre discs to achieve the desired quality of finish,” said Jeff Hanna, national sales manager for Flexovit, Brampton, Ont. “Flap discs are an alternative grinding and finishing product to traditional bonded abrasive grinding wheels and coated sanding discs, offering the characteristics of both the bonded and coated products in one.”

This accounts for significant time and cost savings. Not only does a flap disc eliminate the need to switch out tools, it also lasts longer than resin fibre discs due to its design. In some cases, one flap disc will do the work of several resin fibre discs, ensuring a significant overall cost advantage.

Flap discs also offer ergonomic benefits. These tools provide increased operator comfort and safety because they produce less vibration, less noise, and less dust.

However, flap discs aren’t suited for all applications.

“Having to grind a large portion of metal, like projects in the marine or aircraft industry, a resin fibre disc that can be as large as 9 in. might be a better option,” said Frank Prenda, vice-president of sales and marketing for Gemtex Abrasives, Toronto. “That 9-in. disc will cover a larger material removal area. Because of the familiarity with grinding wheels and resin fibre discs, operators often stick with the standard, but flap discs are becoming increasingly popular because of the unique benefits and wide-ranging applications that they can be used in.”

The design of Gemtex FlapTec Premium allows the operator to grind and finish with one disc, eliminating the need to change abrasive grits. The PPSD version comes with a trimmable plastic back with a 7/8-in. arbor or with a 5/8-in.-11 built-in thread. Gemtex

When it comes to choosing the right flap disc, there are many things that need to be considered. Different flap disc characteristics will directly affect the efficacy and performance of this tool.

“It's in users’ best interest to do research and explore different options available,” said Bell. “Having a flap disc manufacturer come in and explain the benefits of using a new product can be helpful. It’s important to have an open-mindedness for new technology and techniques that can help elevate these tools to a higher level.”

Testing products also can be helpful to understand quality versus price. In some cases, manufacturers can recommend a specific flap disc that can achieve the user’s desired performance for the application.

“Depending on the application and the operators, manufacturers offer different categories of performance,” said Bell. “If you're in a shop doing a small job, you probably don’t need something as high performance, so there are different options to give more price flexibility.”

Shops on the hunt for a suitable flap disc should keep the following characteristics in mind.

Shape. Flap discs are available in two shapes: flat and conical.

“Flat discs, also called Type 27 discs, are preferred for flat surfaces and narrower contact area,” said Hanna.

The Type 27 disc typically grinds best at angles between 0 and 15 degrees, making them better suited for finishing and blending operations. These tools can only be used for slight contours.

“Conical, or Type 29 profile, is ideal for contoured surfaces and broader contact area,” Hanna added.

The Type 29 disc, which often has a built-in angle, allows for more aggressive stock removal.

PFERD Polifan flap discs are used for weld seams, surface grinding, chamfering, deburring and work on fillet welds in steel, stainless steel (INOX) and aluminum. PFERD

Abrasive Grit Material. Certain abrasive grits are better suited for use on specific metals, meaning the workpiece material often will dictate the type of abrasive grit needed.

“Ceramic is the next generation of abrasive grits,” said Bell. “When working with stainless steel workpieces, ceramic is definitely the best choice.”

Hanna added that ceramic coated abrasive cloths provide faster material removal rates, cooler grinding action, and longer life. Because of its high-performance characteristics, it can be used for hard-to-grind materials.

Aluminum oxide, which is the original and standard abrasive grit material, is designed for more general-purpose applications as it offers good performance with a lower price. It is best suited for steel and cast iron.

Zirconia grit falls somewhere between aluminum oxide and ceramic grit in its ability to offer high performance and durability. It is often used for cast iron, carbon steel, structural steel, and stainless steel.

Hanna noted that some manufacturers offer flap discs specifically designed for grinding aluminum. These discs feature stearate coated abrasive strip that prevents soft aluminum from loading on the flap disc.

Grit Size. There are five common grit sizes: 36, 40, 60, 80, 120.

The smaller the grit size number, the larger the abrasive grit, which equates to more aggressive material removal.

For heavy stock removal, 36 to 40 grit is ideal. For weld grinding and some blending, 40 to 60 grit is suggested. Deburring operations generally require 60 grit, while cleaning and finishing operations require 80 to 120 grit.

“One benefit of the flap disc is that you can make a more abrasive grit perform finishing operations depending on how you use it,” said Prenda. “An operator can use a coarse flap disc to remove a lot of material, but through a feathering procedure make this 36-grit flap disc act like a 60- or 80-grit flap disc and perform finishing operations.”

Flexovit Zircotex zirconia alumina discs are suited for high-production grinding, blending, deburring, and finishing on a wide variety of materials including stainless and carbon steel. This grain resists loading or clogging on softer materials such as aluminum, brass, bronze, and fibreglass and are available in Type 27 or Type 29, with a 7/8 arbour or a 5/8-11 spin-on zinc hub. Flexovit

Outside of standard characteristics, flap discs offer enhancements and features that can help boost productivity and expand the range of its efficacy.

“Look at different lengths of flaps,” said Bell. “Conventional flap discs have standard-size flaps, but high-performing-type flap discs have longer flaps, which provide longer life. There also is the radial flap disc that offers three sides of working area. That means you can use the top, side, and bottom of the disc to get into angles of fillet welds.”

Improvements have been made to a flap disc’s backing material as well. For example, most companies now offer fibreglass and nylon as backing materials.

“These are often available with either standard 7/8-in. arbors, or 5/8-in.-11 spin-on threaded adapters,” said Hanna. “The nylon discs offer more rigidity and may be preferred where a more aggressive grinding action is required.”

While fibreglass tends to be the more standard and popular backing option, nylon and plastic backings are trimmable.

“Fibreglass-backed flap discs naturally wear down and will no longer be able to perform properly,” said Prenda. “A trimmable plastic back allows users to trim the outer diameter of the disc that is worn away, extending disc life. Not all manufacturers offer this, but it is something to consider if you have a large application or you want to extend disc life.”

Another advantage of a plastic trimmable back, according to Prenda, is that it offers a low profile, unlike a heavy-duty zinc hub in the centre. The low profile allows it to fit better underneath the guard of a right-angle grinder, ensuring that the protective guard covers it entirely. In some cases, a fibreglass back with a threaded zinc hub may be bulky and protrude below the guard, minimizing the guard’s ability to protect the operator.

The trimmable plastic backing is much lighter for the operator, which is especially helpful if they are using the grinder for many hours in a day.

Another area of innovation are combination flap discs, which incorporate two different types of grit material to achieve the benefits of both.

“For example, a combination flap disc has alternating flaps of zirconia and ceramic,” said Prenda. “The alternating flaps bridge the gap between the performance of a full zirconia and full ceramic flap disc while still keeping it at a lower price point than a full ceramic flap disc. It’s another way to offer an alternative in price and quality.”

Associate Editor Lindsay Luminoso can be reached at [email protected].

Flexovit, flexovitabrasives.com

Gemtex, gemtexabrasives.com

PFERD, pferd.com