by Patrick Lapointe
A step-by-step guide for the perfect finish
Stainless steel is one of the most widely used metals in manufacturing. Its corrosion resistance and other great properties make it a perfect choice for construction, food and beverage, and pharmaceutical industry uses.
This finishing guide focuses on austenitic stainless steel (300 series) due to the importance of eliminating roughness or achieving an aesthetic look in specific applications and industries. Examples include architectural structures, chemical equipment, and food and beverage manufacturing.
1 Clean before you start
Always clean your workpiece before starting any finishing job to remove contaminants on the surface. By doing so, you’ll avoid smearing grease on the surface, clogging the abrasives, and making deeper scratches that will require more work to fix.
2 Start at the finish
Determine the desired finish before you begin the finishing process. This will allow you to map out the process, determine exactly what you’ll need at each step, and avoid any unnecessary steps (for example, repairing deep scratch patterns because the original abrasive was too coarse).
3 Choose the right abrasive
When removing a weld bead from the surface, choose your abrasive carefully. An abrasive that’s too coarse could gouge the surface, making a smooth blend impossible and ruining your workpiece.
4 Watch your grit sizes
To go from a coarse finish to a finer one, do not skip more than three grit sizes at a time. If you need to combine steps, Walter has solutions that can help you do that.
5 Practice cross grinding
Cross grinding is a technique used in finishing and polishing that involves blending in a direction that’s perpendicular to the previous step. Cross grinding is important because it highlights areas where the previous scratch pattern needs to be blended.
6 Pay close attention to pressure and angle
Getting the pressure and angle right when grinding is a must. As a general rule, you should apply more pressure when removing material (taking down a weld, for example) versus polishing. Applying the right pressure and angle keeps the material from overheating and prevents discoloration, surface gouges and warping.
7 Use the recommended RPM
All finishing power tools have variable speed, and each abrasive is recommended for use at a specific speed. It’s important to respect those recommendations so you can achieve a better, faster finish and a guaranteed perfect result without the need for rework. The abrasives will last longer as well; they won’t wear down prematurely, and they won’t glaze or lose their efficiency due to running too slowly.
8 Select the right power tool for the job
The geometric shape of the workpiece is an important consideration because it imposes certain constraints. You need to match the power tool to the shape to do the job effectively. For example, a pipe sander would be best for working on a straight circular tube, but getting to an inside corner will require a fillet weld grinder. Most importantly, you need a variable speed grinder to achieve the best results.
9 Follow standard safety practices
Taking the necessary safety precautions not only prevents accidents, injuries, fatalities, and downtime, but also enhances employees’ health, wellbeing, productivity, and work quality. Ensure you use PPE items for eye, face, hearing, hands and respiratory protection.
When working with a finishing power tool, a safety guard must be in place to protect the operator from the moving abrasive surface and to deflect flying fragments from the workpiece or the abrasive product itself. We strongly recommend unplugging the power tool prior to mounting the abrasive product, and between steps while operators switch products.
10 Finish the process with care
Once you’ve achieved the desired finish and a passive surface, it’s important to remove any dirt, dust, fingerprints, handling marks, and oils, and to protect the surface. SMT
Patrick Lapoint is vice president, research and development, Walter Surface Technologies.