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Preparation: seam assessment and tool selection
Before you start grinding, assess the weld and determine the final result you want. This will determine the number of processing steps and the set of abrasive tools.
Seam evaluation
- Type of seam: butt, fillet, lap joint, T-joint - each has its own processing geometry
- Bead height: from 1-2 mm (thin TIG seam) to 5-8 mm (multi-pass MIG/MAG) - determines whether a roughing stage is needed
- Surface requirements: technical cleaning (2 stages), smooth surface (3 stages), decorative finishing (4 stages)
- Material: carbon steel, stainless steel (INOX), aluminum - each has its own abrasives
Required tool
- Angle grinder (grinder) - 125 mm for most tasks, with speed control for finishing work
- 6.0 mm grinding wheel— for rough removal (grit 24-36)
- Flap discs— P40-P60 for leveling, P80-P120 for finishing
- Fiber disc (alternative) — P60-P120 for finishing
- Non-woven material - for polishing and satin finishing
1 Rough removal of the welded roller
The first stage is the removal of the bulk of the welded bead. This is the most aggressive and productive stage of processing.
- Tool: 6.0 mm thick grinding wheel
- Grit: 24-36 (coarse grit for maximum removal)
- Tilt angle: 15-30° to the surface is the optimal range for grinding
- Pressure: Moderate, let the abrasive do its work. Excessive pressure will overheat the workpiece and wear the wheel.
- Movement: even passes along the seam, do not linger in one place
Result: The weld bead has been removed to the base metal level or slightly above. The surface has a rough texture with characteristic scratches from the grinding wheel. This is normal - the following steps will smooth out the surface.
2 Surface leveling
The second stage removes the marks from the grinding wheel and smooths the surface. The flap wheel works more softly and in a more controlled manner.
- Tool: flap disc
- Grit: P40-P60
- Tilt angle: 15-25° to the surface
- Movement: cross passes at an angle of 45° to the direction of the seam - this ensures even removal
Result: the surface is smooth, without visible welding marks. A uniform texture from the flap disc remains. For technical structures (frames, supports, frames) this may be sufficient.
3 Finishing
The third stage brings the surface to a smooth state. The choice of tool depends on the requirements:
- P80-P120 flap disc is the most common option. Provides a flat, smooth surface, ready for painting or priming
- Fiber disc P80-P120 - an alternative to the flap disc. More aggressive, but with more precise control. Especially convenient for flat surfaces
- Tilt angle: 15-20° - work with the minimum angle in the finishing stages
The result: a smooth, even surface without visible scratches. Ready for painting, priming or further polishing.
4 Polishing (optional)
The fourth stage is required for decorative structures, stainless steel, food industry equipment, and other cases where appearance is important.
- Non-woven material (Scotch-Brite type) - gives a satin finish, masks small scratches. Very Fine or Ultra Fine grit
- Felt wheel + polishing paste— for mirror polishing of stainless steel
- Tilt angle: 10-15° — minimum pressure, maximum contact area
Result: satin or mirror surface, the weld seam is completely invisible.
Summary table of stages
| Stage | Disc type | Grit / Grain Size | Angle | Result |
|---|---|---|---|---|
| 1. Rough removal | Grinding 6.0 mm | 24-36 | 15-30° | Roller removed, rough surface |
| 2. Alignment | Flap | P40-P60 | 15-25° | Smooth surface, uniform texture |
| 3. Finishing | Flap / Fibrous | P80-P120 | 15-20° | Smooth surface, ready for painting |
| 4. Polishing | Nonwoven / Felt | Very Fine+ | 10-15° | Satin or mirror finish |
Features of INOX (stainless steel) finishing
The treatment of welds on stainless steel requires a special approach. The main rule: no contamination with carbon steel.
Rules for working with INOX:
- Only abrasives with the INOX marking - they do not contain iron (Fe) and sulfur (S), which cause corrosion
- Dedicated tools— grinders, wheels, brushes, pads should be used ONLY for stainless steel. Color code the tools
- Clean work area - do not process stainless steel next to carbon steel. Sparks from a neighboring station are already contamination
- Protective film - do not remove the protective film from the stainless steel until all operations are completed
- Reduced RPM - Stainless steel is sensitive to overheating. Discoloration (blue or yellow) means that the chrome layer has been destroyed.
- Passivation - after processing, surface passivation is recommended to restore the protective oxide layer
Typical mistakes when grinding welds
- Too much pressure on the grinder. The abrasive should do the work itself—your job is just to guide the tool. Excessive pressure overheats the workpiece, discolors the metal, accelerates wheel wear, and can cause undercutting of the base metal.
- Incorrect bevel angle. Angle less than 10° — the wheel "sticks", slides on the surface. Angle more than 40° — deep grooves, uneven surface, risk of "cutting" into the metal. Optimum — 15-30° for grinding.
- Skipping grit stages. Going from P36 straight to P120 doesn't work. The rough scratches from P36 will remain under the thin layer processed with P120. The surface will look smooth, but when painted or polished, the defects will show up.
- Using a cutting wheel for grinding. The cutting wheel (1.0-2.5 mm) is only intended for 90° cutting. Side loads can split a thin disc - this is dangerous to life.
- Work in one place. Staying in one spot overheats the metal and creates a local depression. Move the grinder evenly along the seam, at a constant speed.
NovoAbrasive products for seam finishing
NovoAbrasive produces a complete range of abrasive tools for all stages of weld processing:
| Product type | Assortment | Processing stage | Series |
|---|---|---|---|
| Polishing discs | 37 positions | Step 1 — Rough removal | Standard, Profi, Extreme |
| Flap Discs | 62 positions | Steps 2-3 — leveling, finishing | Standard, Profi, Extreme |
| Fiber discs | 12 positions | Step 3 - finishing | Profi |
| Non-woven material | 4 positions | Step 4 - polishing | Profi |
All products are available in carbon steel and INOX versions. The Profi and Extreme series are MPA Hannover certified, a guarantee of safety and performance.
Frequently asked questions
What wheel should I use to clean the weld seam?
For rough removal of weld bead, use a 6.0 mm thick grinding wheel with a grit of 24-36. Work at an angle of 15-30° to the surface. For further leveling, use a P40-P60 flap disc. For finishing, use a P80-P120 flap disc or a fiber disc.
At what angle should the weld be ground?
The optimal angle of inclination of the grinder when grinding is 15-30° to the surface. Too small an angle (less than 10°) leads to overheating and salting of the wheel. Too large an angle (more than 40°) leads to deep scratches and an uneven surface. In the finishing stages, reduce the angle to 15-20°.
How to grind a weld on stainless steel?
When machining INOX, it is critical to avoid contamination. Use only abrasives labeled INOX— they are free of iron and sulfur. Each tool should be dedicated to stainless steel only. Operate at low speeds to avoid overheating and discoloration. Passivation is recommended after machining.
How many steps are required to grind a weld?
2 to 4 stages depending on requirements. Minimum: rough removal + leveling. For structures to be painted: 3 stages. For decorative stainless steel products: 4 stages including polishing. A shallow seam (TIG) can be processed from the 2nd stage.
Why does the grinding wheel wear out quickly when processing a seam?
The most common reasons are: too much pressure (the wheel overheats and breaks down faster), incorrect angle (less than 15° or more than 30°), inappropriate grit (too fine for rough removal). Try the Profi or Extreme series - zirconia and ceramic last 2-3 times longer than aluminum oxide.
Do you need abrasives for seam finishing?
NovoAbrasive — grinding, flap, fiber wheels and non-woven material. A full processing cycle from one manufacturer.