Selecting Abrasives for Welding and Metal Fabrication

Selecting abrasives that make the grade

It is important to realize that abrasive products come in various grades, which some manufacturers designate as good, better and best. Metal fabricators who measure total grinding results and want to achieve the lowest overall grinding cost for an application will seriously consider the “best” abrasive products available and reserve the use of “better” abrasives for high productivity applications, where only abrasive costs are important. End users wanting the lowest initial abrasive costs are likely to select “good” abrasives, but should understand that such a choice may not be as economical in the long run.

Metalworking companies that want to measure total grinding results can work with their abrasive supplier to test and compare abrasives of various grades, or alternative products from different manufacturers. Such tests, performed in a metalworker’s own shop, will reveal relative abrasive cost based on initial cost and wear rate, and can even measure overall worker productivity in terms of worker’s wages. Then, relative abrasive cost can be added to the operator cost to determine the total grinding cost. What such tests typically show is that the most advanced (“best”) abrasive products usually last longer, work faster and may be the most cost-effective choice.

Abrasives Selection Guide

The following are abrasive selection guidelines for typical welding and metal fabrication operations. Products are listed in descending order of 1) best, 2) better and 3) good for the applications referenced:

A Closer Look at Aluminum Applications

In addition to general abrasives selection / application information, here is a more in-depth examination of choosing and using the right abrasive when working with aluminum. In some aluminum manufacturing applications, weld grinding is required in the finishing process for deburring and clean-up. Aluminum weld grinding is a challenging proposition, and the proper abrasives and techniques should be used to ensure the best results.

Aluminum melts easily and has a tendency to coat the abrasive disc, covering the grit and exposing only bits of abrasive. This result generates heat at the point of contact. Continued grinding produces more heat, which produces more melting. And the natural response of the operator is to push harder, causing more friction and greater heat to the disc.

To account for this, there are three main abrasive products used on aluminum: depressed center wheels, fiber discs and flap discs.

Depressed center wheels

These “rocks” are best for deburring and offer the best life. Many manufacturers offer a wheel especially for aluminum. These wheels sometimes contain wax or rubber fillers which helps retard loading on hard-to grind aluminum. 

Fiber discs

These discs are best for clean-up and provide an excellent finish. Many manufacturers offer a disc using zirconia grain for grinding aluminum, which allows sharp cutting points to continue to be exposed through “micro-fracturing” and thus providing more resistance to loading.

Flap discs

These discs combine the best attributes of both depressed center wheels and fiber discs. Flap discs allow for deburring, blending and finishing with one product, saving time and money.

Flap discs have three components: the backing plate, adhesive and abrasive cloth. The abrasive cloth is “layered”, providing a cushioned substrate that produces heavy stock removal rates and surface blending action.

In weld grinding applications, flap discs offer many advantages over depressed center wheels, including:

· higher stock removal rates

· smoother finish

· cooler cut

· lighter weight

· low vibration

· quieter

· ability to deburr and clean in one operation

Similarly, flap discs offer many advantages over fiber discs including:

· up to 20X longer life

· fewer disc changes

· more consistent finish

· reduced loading

· ability to deburr and clean in one operation

Flap disc technology continues to advance.

Aluminum is still tricky to grind and finish, but it’s a lot better with the latest products.

Flap disks are versatile and productive. They can be used aggressively, to cut, or they can be held nearly flat, to finish or blend.