Grahapolisher Metal Finishing Applications and Buffing and Polishing

Test on your jobs

There are many manufacturers of flap discs and wheels, and the best way to find what works for your operation is to test them.

“High-density flap discs like SAIT’s new Ovation flap disc are much more forgiving. There are more flaps packed into the disc, which provides a cushioning feel to the operator. This cushioning effect allows the product to conform to uneven surfaces and minimizes surface gouging, especially on critical parts and pieces. Because there are more flaps, these discs have a much longer life than regular density flap discs,” says Lavigne.

Harbaugh concurs. “Overall flap disc quality depends upon the quality of the backing and the number of flaps on the disc. For example, we have up to 138 flaps on Mercer Abrasive’s Jumbo line where most regular flap discs only have 80 or 90 flaps. The more flaps on a disc, the longer it lasts.”

The experts agree that not all flap discs are created equal. “Safety is a big factor with these products and the fiberglass backing is a key determinant of safety. It is also the most costly component of the wheel. In order to lower costs, manufacturers reduce the number of layers of fiberglass in the fabric, which compromises the integrity of the wheel,” says Lavigne.

Also, the quality of the abrasive material makes a huge difference when it comes to the construction of a flap disc. “Having a consistent product made with only quality raw materials enhances the performance significantly,” Lavigne says.

Use tips

In general, flap disc or wheel users should use one grit coarser than they would normally use with a resin fiber disc. “For example, if they would use an 80 grit abrasive on a job, then we would recommend a 60 grit in order to achieve a similar finish,” says Lavigne.

Users may think that flap discs are only for metal working and blending, but that’s not the case.

“That’s a common misconception about flap discs. With advances in abrasive technologies that offer stronger backings, better grains and stronger resin strength, these products can now do moderate grinding and finishing processes with one disc,” says Lavigne.

But that doesn’t mean these are a one-disc-for-all-jobs abrasive. “We often see users using flap discs in applications where they should not be used, like removing heavy welds. In these instances, the user would benefit from the speed and life of using a bonded grinding wheel and then finishing the weld with a flap disc,” says Lavigne.

Fabrication and welding shops have always used bonded abrasives to rough-grind welds, but flap discs are best for finish work.

“They blend the finish better before painting. The feel of a flap disc while grinding is more spongy because the flaps flex at an angle and float on the material. If you push hard, you remove material, but if you back off, you get more of a buffing action and a nicer finish,” says Harbaugh.

Grit selection depends upon the type of grinding you are doing, says Lavigne.
“What type of grinding needs to be done? If you are removing welds, rust or paint, 36 grit or 40 grit is a good starting point. If you are doing light stock removal and weld blending, choose 60 or 80 grit flap wheels or discs. If you are preparing a weld for paint or a final finish, 120 grit is the best choice,” says Lavigne.

“Aluminum oxide is the most common grit, but if you are working with aluminum or stainless steel, zirconium is the grain of choice due to its aggressive, long lasting nature,” says Harbaugh.

If the work has many sharp corners, the experts also suggest opting for bonded abrasives to do the work because the sharp corners can easily damage the flap wheel or disc and shorten its life.

Finally, Benincaso says it’s important to watch your speed when using these tools.
“Often, the user assumes that flap wheels are made to run as close to maximum speed as possible without going over the maximum rpm. Actually, the optimum operating speed is significantly less. The maximum rpm only indicates safe operating flap wheel speed. When flap wheels run too fast, centrifugal force makes the flaps very rigid and allows only the tips of the flaps to contact the work piece. When the flap wheel runs at the proper speed, the flaps have a chance ‘lay’ down on the work piece. This gives more surface area that contacts the work piece and provides optimal performance,” says Benincaso.

·	Abrasive training : Proper Use of Grinding Wheels
·	Choosing a Flap Wheel Diameter and Width
·	How to Choose a Flap Wheel Grit Size
·	Flap Wheels - Working with Flap Wheels
·	Metal Finishing and Buffing of Steel & Stainless Steel
·	Metal Finishing Applications / Buffing and Polishing

·	Mounted Flap Wheels - Gp1
·	Flap Discs - Gp2
·	Flap Wheels Un-mounted - Gp3
·	Grinding/Radial Wheels - Gp4
·	Flexible Discs - Gp5