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For most metalworking, a 4½-inch (115 mm) angle grinder with a 7–11 amp corded motor is the most versatile disc grinder; choose a 5-inch model for more reach, a 6-inch grinder for faster stock removal, or a compact cordless grinder when mobility matters more than long runtime. The right choice depends less on headline power than on matching disc size, machine weight, and guard adjustment to the work you actually do.
What we cover
Disc grinder comparison: choose by job, not just motor size
Here, “disc grinder” refers to a handheld angle grinder used with compatible abrasive, cutting, or finishing discs. Check the tool’s manual before fitting any accessory: spindle, flange, speed rating, disc diameter, and guard must all match. The figures below describe common tool classes, not specifications for every model.
| Grinder class | Typical power | Common disc size | Typical bare weight | Best suited to | Main trade-off |
|---|---|---|---|---|---|
| Compact cordless | 18–20 V battery platform | 4½ inches (115 mm) | 4–6 lb (1.8–2.7 kg), excluding battery | On-site repairs, short cuts, and work away from outlets | Runtime and added battery weight |
| Standard corded | 7–11 A; roughly 840–1,320 input watts | 4½ inches (115 mm) | 4–6 lb (1.8–2.7 kg) | Fabrication, deburring, and routine cutting and grinding | Power cord can snag or limit reach |
| Large 5-inch corded | Typically 10–13 A | 5 inches (125 mm) | 5–7 lb (2.3–3.2 kg) | Deeper cuts and broader grinding passes | More bulk; accessory and guard compatibility matters |
| 6-inch corded | Typically 12–15 A | 6 inches (150 mm) | 6–9 lb (2.7–4.1 kg) | Frequent heavy grinding on larger workpieces | Greater fatigue and less access in tight spaces |
Weight ranges are approximate and vary with handle, guard, and battery. Amp ratings show electrical input, not the force delivered at the disc. For cordless tools, battery capacity (amp-hours) affects runtime, while battery voltage alone does not tell you how long a charge will last. Brushless motors can make efficient use of a battery, but they do not eliminate the limits of a small disc or battery pack.
Which disc grinder fits your metalworking?
For an occasional home repair or beginner setup
Choose a standard 4½-inch corded grinder with a tool-adjustable guard and a comfortable side handle. It is generally less expensive than a comparable cordless setup, and you can work continuously without managing batteries. For occasional use, paying extra for a larger grinder may add weight without making the work easier. A rough general market range is about $40–$120 for a basic corded grinder, excluding accessories.
For regular fabrication and mixed tasks
A 4½-inch grinder remains a strong all-rounder if your work includes tack weld cleanup, edge preparation, and cutting smaller sections of stock. Consider a 5-inch machine when you often need a deeper cut or wider grinding path. Look for a readily adjustable guard, a spindle lock that is easy to reach, and a switch you can operate safely while maintaining a firm grip. General market ranges are roughly $70–$180 for corded models and $100–$250 for cordless tools sold without a battery; kits usually cost more.
For heavy stock removal or larger steel
A 6-inch grinder can cover more surface per pass and accept larger compatible accessories, making it useful for repetitive work on substantial welds or plate. The added reach is not a substitute for using the right abrasive, and the extra weight can make overhead or precision work tiring. Buy one if the workpiece size and frequency justify it—not simply because the motor has a higher amp rating. General market prices for this class commonly range from about $100–$300, depending on features and configuration.
For mobile work and short jobs
A cordless 4½-inch grinder is convenient for repairs, site work, or a shop with limited access to outlets. Compare the complete working weight with the battery installed, not just the bare-tool figure. If you cut and grind for extended periods, budget for spare batteries and charging time. A battery platform you already own may make the tool a much better value; otherwise, the battery and charger can make a cordless purchase substantially more expensive than the tool-only price.
Power, disc size, and guard design: what to check before buying
- Power for sustained work: For corded models, a higher amp rating can be helpful during demanding, continuous grinding, but technique and disc choice still matter. A grinder that bogs down can leave rough results; do not force the disc to compensate. For cordless models, check whether the manufacturer specifies a compatible high-capacity battery for demanding work.
- Disc size and cutting depth: A larger disc can reach farther into a cut, but actual depth depends on the tool’s guard, flange, and accessory. Never remove a guard or use an accessory beyond its rated diameter. Verify that replacement discs are easy to source locally.
- Weight and balance: A lighter tool is easier to control during extended or awkward work. A heavier tool may feel stable in a two-handed pass but can increase fatigue. If possible, assess the grip and side-handle positions with the battery fitted.
- Guard adjustment: A guard that can be repositioned without a separate wrench makes it easier to direct sparks away from you and reposition the shield as the work changes. It must lock securely; convenience is not worth a guard that shifts during use.
- Speed and accessory rating: Match the accessory’s maximum rated speed to the grinder’s no-load speed and follow the accessory maker’s instructions. A cutting wheel, grinding wheel, and flap disc are not interchangeable just because they fit the spindle.
Ownership realities: discs, dust, and wear
A low tool price does not necessarily mean a low cost per job. Abrasive discs are consumables, and the wrong type can wear out quickly or damage the work. As a simple planning example, if a pack of 10 discs costs $20, the disc cost is $2 per disc. A job that uses three discs therefore consumes about $6 in discs alone, before accounting for labor or tool wear. Actual consumption depends heavily on material, pressure, and disc quality.
On many grinders, the consumable accessory wears first, followed by components affected by abrasive dust, such as vents, switches, and bearings. Keep the tool’s air openings clear, follow the manual’s cleaning guidance, and store it away from grinding debris. Do not direct compressed air into the tool unless the manufacturer recommends it; this can push dust farther inside. Replace damaged cords, cracked guards, or worn accessories rather than continuing to use them.
Common avoidable mistakes include leaning too hard on the disc, using a cutting wheel for side grinding when it is not rated for that use, and choosing a wheel with a lower speed rating than the grinder. Let the accessory do the work, keep the workpiece secured, and disconnect a corded tool or remove the battery before changing discs.
A quick decision matrix
| Your situation | Practical choice | Reason |
|---|---|---|
| New user; occasional, light work | 4½-inch corded grinder, about 7–9 A | Manageable size and no battery investment |
| Frequent shop work across several tasks | 4½- or 5-inch corded grinder, about 9–13 A | Good balance of continuous power and access |
| Repeated heavy grinding on large pieces | 6-inch corded grinder, typically 12–15 A | Larger compatible discs can cover more area |
| Repairs away from outlets; short work sessions | 4½-inch cordless grinder with a spare battery | Portability without a cord trailing across the work area |
| Tight spaces or extended overhead work | Compact 4½-inch model with a lower working weight | Smaller form and reduced fatigue improve control |
Bottom line
For a first or general-purpose disc grinder, start with a 4½-inch corded model if you work mainly in a shop, or a cordless version if mobility is essential. Step up to 5 or 6 inches only when the extra cutting reach or grinding coverage will be used regularly. Before buying, compare the tool’s actual weight, guard adjustment, accessory compatibility, and the cost of consumables—not just its power rating.
Grinding and cutting throw sparks and fragments. Use the protective equipment specified by the tool and accessory manufacturers, secure the workpiece, and keep flammable materials clear. Follow the grinder manual for guard use and operating technique.
