Stainless steel is still a relatively new product only having been around for about 100 years unlike it's more traditional counterparts, iron, and mild steel. Stainless steel's breakthrough in corrosion, rust resistance, and durability has made it a material that has found its way into just about every aspect of our lives. It is found in places you might not generally think, but with these amazing properties comes the challenge of putting an outward finish on it worthy of its contribution to society.
Most parts will be welded or joined in some fashion. Leveling the weld is paramount in creating that sleek and high end look. Typically most weld leveling operations are done with abrasive discs. However not all discs and abrasive formulations are suitable for stainless steel. The recommendations below all feature an abrasive grain mixture that is suitable for stainless steel grinding. You can learn more about abrasive grain formulations found in all types of grinding discs in this article. Depending on the type of weld, ease of access will determine what form of disc to use.
AbrasiveBoss Product Recommendations:
Better: 3M 787C Fibre discs
Best: 3M 987C Fibre discs
Use with a hard density (black) face plate or backup pad
Alternative selections:
Better: 3M 769F Flap discs
Best: 3M 967A Flap discs
Better: 3M 777f Roloc discs
Best: 3M 984F Roloc discs
Learn more about disc attachments and face plates here.
AbrasiveBoss Finishing Hot Tip!
Use the finest grade of abrasive that gets the job done; finer grind lines are easier to remove. Always align the grinding scratches with the grain of the workpiece. This will make it easier to blend the scratches in later steps. Perpendicular grind lines are more difficult to blend.
Setting the grain is a process of generating a directional grain pattern. This step begins the process of preparing the stainless steel for final finishing. This step can be one of the more tedious steps as a mistake here can make refining the desired scratch pattern for the final look of the workpiece. While product selection is important, even more so is the technique and the right tool.
AbrasiveBoss Product Recommendations:
Better: 3M 777F 120 grit 3-½ inch X 15-½ inch belt on a Inline sander
Best: 3M 947A 120 grit 3-½ inch X 15-½ inch belt on a Inline sander
Alternative selections:
3M 747D 80 or 120 grit Flap Wheel on a die grinder (18,000 RPM) great for small or tight access
3M 775L 120 grit 5 inch discs on a random orbital tool great for reasonably large flat areas when a non-directional final finish is desired
AbrasiveBoss Finishing Hot Tip!
Try and stay as close to the weld as possible. This will minimize the final blending needed near the weld areas. These areas will have the deepest scratches from the previous step of leveling the weld. Test the chosen grit as deeper scratches from coarser grits will take more time to more time in the surface condition step.
The final finish is all about aesthetics. There is a loose standard across the industry to define and categorize the finishes on stainless steel. The finish number (#) determines the general aesthetic look of the final product. Following this brief explanation will be some recommendations on how to achieve each finish level.
Stainless Steel Finish 2B (Bright, Cold Rolled)
A bright, cold-rolled finish is the most common on stainless steel. It resembles a very hazy mirror, with some reflection evident. 2B is typically how "raw" sheets come to the fabricator for processing.
Stainless Steel Finish #3 (Brushed)
An intermediate polished surface obtained by finishing with a 120-grit abrasive. A directional course "grain" running in one direction.
Stainless Steel Finish #4 (Brushed)
A polished surface finer than #3. This is a general purpose bright finish with a visible directional “grain” which prevents mirror reflection.
Stainless Steel Finish #5 (Bushed, reflective)
A polished surface finer than #5. This is a higher shine or reflectiveness than #4 and a less visible grain direction.
Stainless Steel Finish #8 (Mirror)
The most reflective surface of stainless steel commonly available, It is produced by polishing with successively finer abrasives and buffing extensively until all grit lines from preliminary grinding operations are removed.
AbrasiveBoss Product Recommendations:
3M Scotch-Brite Surface Conditioning belt 3-½ inch X 15-½ inch on an Inline sander
Grade: A Coarse for #3 finish
Grade: A Medium for a #4 finish
Alternative selections:
3M Scotch-Brite Multi-Finishing wheel (various sizes)
Grade: 2S Coarse for #3
Grade: 2S Medium for #4
3M Trizact 3-½ inch X 15-½ inch on an Inline sander
Grade: A100 for #5
Trizact is a special 3M proprietary abrasive structure that is ideal for polishing. It comes in a wide range of material types to dial in #5-#8 finishes.
AbrasiveBoss Finishing Hot Tip!
Finish a small area on the corner of the workpiece. Examine the finish from all angles. This will determine if you are going in the right direction with the finishing technique and abrasive choice. With practices you can feather in and out of the repair area. Use the longest strokes that are comfortable and ease up on the pressure on each side of the stroke.
Final blending or touch up work can be done with Scotch-Brite hand pads. The most common hand pads for this work are the 7446 and 7447 to blend in the feathered areas or to touch up light damage or scuffs.
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