Right-Angle Grinding in Welding Operations
Right-Angle Grinding in Welding Operations:
Doing It Right and Doing it Safely
By: Debbie Gaspich, Product Manager, Welding Grinding Products
There now are more and more products that can be used with the right-angle grinder, and the tool is becoming more and more useful because of the wider range of products available. This article provides information on the products available, what to use for what application, and how to use these products safely and efficiently.
Using the right disc or wheel for a grinding job and doing the job safely is more productive in the long run than simply using whatever abrasive product is handy or moving ahead without taking appropriate safety precautions. So, let’s take a look at some of the abrasive products currently available for use on right-angle grinders for welding-related jobs and then review the measures you should take to ensure their safe use in your work.
Selecting the Wheel or Disc for the Job
For cutting structural steel, pipe, sheet metal, and other profiles with a right-angle grinder there are reinforced cut-off wheels. Choices include wheels with a premium blend of abrasives for maximum productivity and mid-range wheels featuring a durable zirconia alumina blend. The latter wheels outperform standard aluminum oxide wheels, which themselves offer high-to-medium cut rates in general-purpose applications.
Cut-off wheels for right-angle grinders are available with depressed centers (Type 27) and flat configurations (Type 01). Be aware that there are safety considerations associated with using flat cut-off wheels. Specifically, they should be mounted on right-angle grinders only when the proper cut-off guard and equal size flanges are used. Before using flat cut-off wheels on your machine, contact your grinder supplier for the proper guards and flanges.
For material removal, including weld grinding, blending, deburring, and finishing, using coated abrasive fibre discs. A variety of premium quality discs are available for finishing various metals. For example, a seeded gel (SG) ceramic formulation offers an outstanding initial cut rate. A self-lubricating formulation provides outstanding finishes on stainless steel and steel alloys. And a more versatile premium product provides finishing on carbon steel, mild steel, and cast iron. Other fibre discs include a self-sharpening zirconia alumina product for aggressive cutting, a ceramic alumina disc for heavy stock removal and another zirconia alumina formulation for use on stainless steel. For general-purpose applications, there are aluminum oxide discs.
There are fiber discs, called AVOS (Allows View of Surface), that have holes in them to let you view surfaces as you grind. With this product, the grinder is held at a 5 to a 15-degree angle, so the operator uses more of the cutting surface of the disc, and achieves a more aggressive cut for more stock removal and a smoother surface with less gouging. Besides more precise grinding, these discs also offer cooler cutting and airflow that pulls away loose, disc-clogging abrasive and swarf, thereby extending disc life.
For heavy stock removal, including weld grinding and pipe beveling and repair, use depressed center grinding wheels. These wheels are similar to the depressed center cutting wheels described earlier. One type of depressed center wheel that should be of interest to you as a welder has a combination of ceramic alumina and zirconia alumina abrasives that delivers a fifty percent better-cut rate and nine times the life expectancy of an aluminum oxide wheel. These top-of-the-line wheels are excellent on all grinding jobs from gray iron to exotic alloys and stainless steel.
In the mid-price, mid-performance range is wheels with a high percentage of zirconia alumina abrasive blended with aluminum oxide. These wheels offer twice the service life of aluminum-oxide-only products and provide a good performance-to-price ratio that lowers the total cost of using them. Of course, economical aluminum oxide depressed center wheels are available in various formulations for a variety of applications.
Also available in the mid-performance range are depressed center AVOS wheels with aluminum oxide grains formed into unique patterns. These see-through wheels have a convex (Type 29) design and supply all of the benefits of the AVOS fibre discs described earlier.
To get maximum performance from a depressed center wheel, you should run your grinder at the highest possible speed marked on the wheel. Also, these wheels should be run at the correct angle. In fact, most grinding wheels and discs perform best when running at a specified angle or within a range of angles, and some can be damaged when a maximum angle is exceeded. Always check information supplied with a grinding product or consult the supplier’s catalog or technical staff to determine the most productive and safest grinding angle for a specific product.
For blending and finishing welds in one step with medium-to-light stock removal use coated abrasive flap discs. These products also work well for chamfering edges, deburring, and cleaning.
Top-of-the-line flap discs have a ceramic and zirconia alumina abrasive blend and are available in two configurations: flat (Type 27) or conical with an angled face (Type 29). Both offer outstanding performance on stainless and carbon steels.
Mid-performance flap discs with zirconia alumina abrasive have relatively long service lives, as much as 30 percent longer than aluminum oxide products. They are available in the two configurations already mentioned as well as in high density, jumbo (thicker) models, which are more robust than standard Type 27 discs and last as much as 40 percent longer.
Conical flap discs are intended for more aggressive grinding than are flat discs, and flat flap discs are the better choice for fine finishing. Recently, high-performance zirconia alumina flap discs were introduced to the marketplace. Available only in flat configurations, they offer a combination of fast stock removal and fine finishing.
For surface preparation and cleanup, including the removal of rust and corrosion, light weld spatter and mill scale, use strip discs and depressed center wheels made for such purposes (e.g., Saint-Gobain’s Bear-Tex® products). These products are an open web of thick, strong synthetic fibers and extra course abrasive held together by a smear-resistant adhesive. These products conform easily to difficult part profiles and uneven surfaces while minimizing loading on grinders.
Last, But Not Least - Safety First
Every worker, hobbyist, or artist who picks up a right-angle grinder should be generally familiar with ANSI Safety Requirements B7.1 and B7.7. If you don’t have a copy, your abrasive products supplier will provide one. Also, these same suppliers always provide written safety procedures with their products. The guidelines often appear on products and packaging immediately after a prominent "Warning" icon. Read all warnings that accompany grinding wheels and discs, and comply with them.
In general, grinding safety considerations fall into four categories: 1) using appropriate personal safety equipment, 2) matching the abrasive to the equipment as well as to the job, 3) grinding safely and 4) maintaining both the equipment and grinding media (wheels and discs).
The use of personal safety equipment is mandatory because grinding creates metal particles and sparks, dust, particles of abrasive, and (if a grinding wheel breaks during use) pieces of shrapnel flying around at high speed. Given these potential hazards, it’s important that personnel using right-angle grinders wear face protection and eye protection. Safety gloves and leather aprons should also be used along with the appropriate respiratory protection (dust control system, mask, etc.) for the material being ground. And since grinding can be a noisy operation, hearing protection must be worn when noise exceeds mandated thresholds for loudness and duration.
Matching the equipment, the abrasive product, and the job entails more than simply picking up a catalog and selecting a wheel or disc listed for the appropriate application. On right angle grinders, use only grinding products made for use on right-angle grinders. Be sure the product is a “fit” for your machine in terms of both size and speed. Don’t run a wheel beyond its recommended speed or use a wheel that is too large for a machine. And never alter a guard to accommodate an oversized wheel or disc. Inspect every wheel before you use it, and test run it for a minute while standing out of the plane of rotation. This latter test will help ensure that if a wheel is cracked and breaks the operator will not be injured.
Grinding safely means that you understand how to correctly mount abrasive devices on a right-angle grinder and will do it correctly. It also means that you never mount or remove a wheel or disc without disconnecting power to the grinder. When actually grinding, you make sure that the guard is positioned correctly to protect you and bystanders. You also make sure any spark stream you create is not hitting yourself, another person, or any flammable materials.
Maintaining grinders and grinding media helps you avoid injuries and increases your productivity. Give electric grinders monthly checkups and check their rotational speed with a photo or contact tachometer after any maintenance or repair. Check the rotational speed of governor controlled air driven grinders every 20 hours of actual use or once per week, whichever, comes first and after maintenance when issued from a tool crib or at each wheel change. No one wants grinding wheels flying apart and causing injury because they are running too fast.
Properly maintaining grinding media, especially grinding wheels, entails storing them properly when new and between uses, inspecting them before each use, and treating them with care in all cases. Rough treatment of grinding wheels can break or crack them, making them dangerous when used.
Whatever the welding-related application, there is an abrasive product for use with your right-angle grinder that will be your best investment in terms of price and performance. Ultimately, selecting the correct disc or wheel and using it safely is your responsibility, but if you have any doubts or questions contact your abrasive products supplier.
Source:
Saint-Gobain Abrasives, Inc.
1 New Bond St
Worchester, MA 01615
