Welding requires careful prep work, the right filler materials, and a decent amount of finishing. The aim is to get strong and clean welds that not only look good, but also have the required strength to stand the test of time. While choosing the right welding machine is usually straightforward, the tools and accessories for clearing the workpiece from rust or removing weld spatter and slag after the weld is created involve careful choices.
Welders often use wire brushes when cleaning the workpiece before welding, and chipping away at abundant spatter and slag deposits with an aptly named chipping hammer. To get cleaner and better-looking surface finishes, there’s also the choice between sanding discs, flap wheels and grinding discs.
Sanding Disc Basics
Welders have three grinder accessories when prepping workpieces for welding and getting the desired finish. Grinding discs are used for their heavy stock removal and quick results with weld beads, burrs and rust. Flap wheels offer more versatility, combining both grinding and finishing tasks with more detailed, contoured and smoother surfaces. For fine finishes, welders turn to practical sanding discs for grinder. This is a versatile grinder attachment that’s also used in pre- and post-fabrication tasks, including:
- Removing weld seams – These grinder attachments are effective in removing excess material such as slag in weld seams and producing more aesthetically pleasing and flush surfaces.
- Removing surface imperfections – Get rid of gouges, grooves and other surface imperfections with sanding discs in the right grit. The discs are used for finishing tasks on coarse surfaces left behind with grinding wheels or coarser flap wheels.
- Weld blending – For a more uniform look, sanding discs help blend the weld into the surrounding metal.
- Prep and edge work – Remove rust, mill scale, and other imperfections before welding. The attachments are also good at getting finer finishes with ungainly burrs and sharp edges, necessary for tighter tolerances and improved looks.
- Polishing – Discs in finer grit are used for smoothing, sanding and polishing tasks.
Different Types of Sanding Discs
Resin Fibre
These consist of resin-bonded abrasive grains and a vulcanised fibre backing. They attach to grinders with an appropriate backing pad. Discs can be sourced in varied materials and grit, and used for a variety of tasks, ranging from heavy stock removal and general sanding to surface blending and rust removal.
Hook and Loop
Hook and loop sanding discs are made of cloth or paper coated abrasive and an adhesive backing. They attach to grinders and sanders via a system of hooks and loops, ensuring quick disc changes without sacrificing precision or time. The discs come in a variety of sizes and grits, allowing for versatility in different welding tasks.
Quick Change Discs
For tight spots and precision work, welders opt for quick-change sanding discs for grinder. As the name implies, these have a quick-release system, such as threaded hubs or snap-on designs, that easily attach the disc to the tool. They’re effective in deburring, levelling, surface weld blending and smoothing.
PSA Discs
Pressure-sensitive adhesive discs are common in smash repairers and auto shops. They have an adhesive backing for simple attachment, and are primarily used in blending, smoothing, rust removal and prepping metal surfaces for painting.
Other types include heavy-duty semi-flexible sanding discs, consisting of a silicon carbide abrasive facer material and a semi-flexible backing. The design is effective in heavy stock removal, especially for pronounced weld slag and rust. For cleaning, surface prep, rust removal and weld blending, also consider the variety of surface conditioning discs. These differ from the abovementioned types in that they have nylon fibres laced with abrasive materials, preferred for their limited damage to the base material and efficiency.
Abrasive Materials, Grit and Other Buying Considerations
Grinding, sanding and polishing are done by the abrasive materials embedded in the disc. These come in different materials, each with its own set of advantages and limitations.
Aluminium Oxide
An affordable, versatile, durable and general-purpose abrasive good for smoothing, sanding and surface prep in various metals, including mild and alloyed steel, aluminium and copper alloys, like brass and bronze.
Zirconia Alumina
This has higher strength and is suitable for stainless steel, cast iron, and titanium. The abrasive has a longer lifespan, higher heat resistance and is suited to more aggressive grinding and stock removal.
Ceramic
An all-purpose, extremely tough material for demanding sanding applications. Ceramic discs are the go-to choice for grinding harder metals, such as unalloyed steels, stainless steel, nickel and cobalt, due to its high durability, self-sharpening properties and heat resistance.
Other materials are silicon carbide, another self-sharpening abrasive commonly used in brazing applications with bronze and brass, and non-woven nylon abrasives in fine sanding tasks. When buying discs and sanding wheels, also consider grit, or how coarse or fine the abrasive materials are.
This is stated in numbers, with lower grit indicating a coarser abrasive suitable for high-speed and heavy stock removal, and higher grit numbers for smoothing, blending and finishing tasks. Lastly, get discs in the right size. Smaller, 5″/125mm discs are suited to precision sanding, while 6″/150mm and 7″/175mm or larger for heavy material removal across wider surfaces.