Sourced from the Welding Journal, January 2008 issue
Are you interested in weld finishing, but unfamiliar with the tools and accessories needed to get the job done successfully? Well, you’ve come to the right place. Read on for tips and hints to help you conquer your weld finishing jobs as easily as possible. Just grabbing any old tool and embarking on a weld finishing project could lead to disaster with poor, weak joints and wear and tear on both the tool and the operator. Prior to weld finishing, the user must be familiar with the safety requirements and the tools commonly used for this technique, including burnishers, die grinders, and angle grinders as well as their related accessories and abrasives.
If you want to survive the job in one piece, first start by properly equipping yourself with the personal protective equipment (PPE) needed. Grinding creates hazards that include sparks and flying debris, so safety glasses or a full-face shield are needed. Grinding is also a noisy job, so hearing protection is required. To protect yourself from sparks and debris, leather work gloves as well as a leather apron or full shop coat are recommended. Depending on the material being ground, a dust mask or respirator should also be used. Always be sure the tool has been properly maintained, and read and understand the instruction manual that comes with the tool. Never operate the tool without guards and side handles in place.
For optimum performance, greatest efficiency, and quickest throughput for weld finishing, you must choose the proper grinder for your welding application. Many manufacturers offer an array of grinder models. Grinders come in many sizes — 4 1 ⁄2 , 5, 6, 7, and 9 in. — and in different switch configurations: top-locking switch, side-locking switch, rear-locking paddle switch, or a “dead man” non-locking paddle switch. Ergonomics and your shop rules will determine which type suits you best. Grinders also come in various power ratings and speeds that allow you to match the ideal tool with an application. For example, a 9-in. angle grinder may be too cumbersome in tight situations, and a 41⁄2- or 5-in. grinder could be too lightweight to grind stainless steel welds; therefore, an all-purpose 6- or 7- in. angle grinder in would be an ideal fit. Most shops own some finishing tools such as a small angle grinder (41⁄2 in.) for light grinding, deburring, and sanding applications as well as a large angle grinder (7 or 9 in.) for heavy material removal applications. Be aware, however, the weight of the grinder should be considered when selecting one that is suitable for the welding application. Grinders can weigh as little as 4.5 lb and as much as 19 lb, which makes a drastic difference when working on a ladder or removing welds on a vertical surface.
Hitting Your Stride
The burnisher is a useful tool for weld and surface finishing with its exceptional ability to grind/blend welds as well as to create a brushed or polished look on bronze, steel, nickel, silver, and stainless steel. Standard features on many available burnishers include durable sanding and abrasive belts that are utilized for sanding, smoothing, buffing, and polishing metal. More upscale burnishers offer advanced features; for example, Metabo’s SE 12-115 burnisher provides electronic speed stabilization and spiral bevel gears, ensuring consistent results and an efficient transfer of power when finishing welds. Many manufacturers also offer an accessory line to complement their burnishers, further optimizing the tool for each specific application.
The die grinder is a versatile tool that can be used for situations such as deburring and cutting as well as for finishing and light grinding of welds. With higher revolutions per minute (rev/min), single-speed die grinders featuring no-load speeds from 20,000 to 30,000 rev/min are best for deburring using mounted abrasive points or carbide burrs. Variable speed die grinders, with ranges from 7000 to 27,000 rev/min, can tackle various applications like delicate finishing and blending by using a lower speed and 2- to 3-in. wafer cutting wheels. Some die grinders also feature geared down construction that provides higher torque and, along with larger accessories, are ideal for covering more surface area when finishing and blending welds. Typical accessories for die grinders include abrasive mounted points that are ideal for grinding applications and are available in a large variety of shapes, such as cylindrical and cone, mounted to a 1 ⁄4-or 1 ⁄8- in. steel shaft. Carbide burrs, used for metal removal and deburring, also come in a variety of shapes and sizes, typically with 1⁄4- in. shank size. Other accessories for die grinders include flap wheels offered in standard, nonwoven, and interleaved versions. Standard flap wheels are ideal for material removal, but leave a rougher finish; nonwoven wheels provide a nicer finish, but do not do a good job in removing stock; and interleaved wheels provide a smoother finish when used for surface conditioning and blending. It is critical to choose the proper accessory when weld finishing. For example, if you are trying to remove a hard metal by using an accessory meant for lighter duty applications, this accessory will not hold up well under pressure and may damage the project, or even worse, result in injury. When the proper accessory is chosen, the life of the accessory and the efficiency of the operator increase dramatically, saving both time and money.
Angle grinders offer an array of features that enhance tool performance as well as user comfort and safety. For example, one model offers a two-position ergonomic side handle, lock-on switch, easy-to-use accessible spindle lock, lowprofile aluminum die cast gear housing, and high-efficiency cooling vents with front exhaust. Electronics can also enhance the performance and add safety features to these tools. Electronic speed stabilization keeps the grinding wheel spinning at the optimum speed, even under full load, saving time and effort in the grinding job. Overload protection warns the operator of impending overload and prevents the tool from burning up. A power interruption feature also disables the tool in the event of a power outage while in operation, preventing unexpected restart when power is restored. With its ergonomic design, the small angle grinder is ideal for weld finishing in hard-to-reach places. Angle grinders are available in many sizes, and more specifically, a smaller grinder, measuring 4 1 ⁄2, 5, or 6 in., is perfect for grinding out welds in odd positions such as from atop a ladder or inside a vessel. Prior to choosing your angle grinder, you must first consider the various performance specifications of each model. For example, Metabo’s 6-in. W14-150 and 9-in. W25-230 models share many features, such an ergonomic rear handle that pivots 90 deg left and right, a three-position side handle, auto-stop carbon brushes, and tool-less guard adjustment. However, the available torques are 44 lb in the 6-in. model and 150 lb in the 9-in. model. You should compare the different models in order to choose the right tool for the application. An assortment of specialized abrasive wheels is also available to grind, blend, or clean any welding application. When choosing a wheel, the wheel size must match the grinder size and its maximum rev/min should always be rated at or above the no-load speed of the angle grinder to ensure maximum performance and safe operation. To ensure safety, the user should consult the grinder manufacturer so the right abrasive is used based on the grinder model.
The Finish Line
The angle grinder’s abrasive wheels are the working force behind all weld-finishing applications. Using the correct grinder/wheel combination will ensure the greatest efficiency, performance, and results. Abrasive wheels fall into two broad categories: grinding wheels and slicing (cut-off) wheels. A grinding wheel is thicker, sturdier, and designed to grind down and blend welds, so the wheel is typically applied at an angle of 15–30 deg to the surface being ground. In contrast, a slicing or cutting wheel is always used perpendicular to the material being cut. To choose the best abrasive for weld finishing, the user must understand the different types of abrasives and their uses. It is also important to match the wheel carefully to the stock being ground. There are three major types of abrasives to choose from, which are determined by the application’s surface:
- Aluminum oxide is a general-purpose abrasive for use on ferrous metals. It offers good wheel life, good material removal rates, and comes in varying degrees of hardness for job-matched performance. For hard materials such as stainless steel, users should select a softer grade abrasive, while a harder grade abrasive is suitable for softer metals because it will not dull the grains as readily.
- Zirconia alumina is used for ferrous metals, stainless steels, and high tensile strength alloys. It offers superior wheel life and superior material removal rates.
- Silicon carbide is used for nonferrous metals such as copper, aluminum, bronze, and masonry materials.
Grasping the Silver Metal
Overall, when selecting a tool, abrasive, or accessory for weld finishing you must first consider the application at hand, including the type of metal you’re working with, desired finish, and working conditions. The weld finishing tips found here will help you choose the proper tools, abrasives, and accessories that will complement your application and provide you with the ability to get the most out of grinding and finishing welds.