Weld Removal & Finishing
The right sequence of abrasives can successfully achieve a seamless appearance
on welded carbon steel. Select among products and techniques that are most
compatible with the final finish and are compatible with paint system
Depending on the paint system, available tools and desired outcomes, there are
multiple ways and products to choose from in achieving a carbon steel finish that
can be painted or coated. The following process is recommended as an excellent
starting point for rapidly achieving good finish results on carbon steel welds.
Step 1: Level the Weld
Begin with 3M™ Cubitron™ II Disc 982C on a right angle grinder to level the weld. Choosing grade 50 for this step
should allow you to proceed directly to blending the scratches in step 2. If heavier stock removal is required
a coarser grade should be used first, followed by grade 50 before proceeding to step 2.
Select a backup pad with the appropriate flexibility for the job and note the speed rating for each backup pad. The
maximum operating speed for a standard 7" disc is 6000 rpm. Always inspect discs and backup pads for damage.
Replace if damaged or worn. Never run the disc without a backup pad. Do not exceed the maximum operating
speed (MOS) rating of the backup pad. Always match the recommended backup pad to the disc diameter.
Bring the fibre disc in contact with the workpiece at a 7-10 degree angle. Always try to use as much surface
of the disc as possible. On your final pass over the workpiece, lighten up on the pressure to minimize the
Step 2: Blend the Scratches
In the second step, use a rotary tool to blend the scratches. Selecting a Scotch-Brite™ Surface Conditioning
Disc in grade ACRS offers long-life and is a user friendly and “forgiving” option for blending. The 3M™ Backup
Pad 917FD is well suited for more aggressive applications and products. For better security, press the disc onto
the benchtop and run the tool to help lock the disc in place. The Scotch-Brite disc will not gouge the metal
so operators can get good results regardless of their level of experience. This finish may be an acceptable
Tech Tip: To extend the life of the product, sweep the edges of the workpiece with the disc.
An economic alternative to the Scotch-Brite disc is the use of an 8" 3M™ Stikit™ Disc 751I, also used on a rotary
tool. For maximum adhesion, make sure the backup pad is clean and free from dust. Use a disc in grade 80 to
follow the grade 50 fibre disc. This finish may be an acceptable stopping point, depending on the location
of the weld or paint thickness.
Tech Tip: Arule of thumb when sequencing coated abrasives on rotary tools is that you may skip every
other grade in the sequence, as we are skipping grade 60 here.
A rotary tool is a quick way to blend scratches from the previous step. It leaves a coarse finish with rotary
patterns which may require a thicker coating of paint to cover.
Step 3: Final Finish
To generate a finer finish and more randomized scratch pattern, after using a 751I Stikit disc on the rotary tool,
add a final step with the same grade of 751I on a random orbital sander. 751I contains 3M™ Cubitron™ Abrasive
Grain and is a long-lasting alternative to aluminum oxide discs. A5" disc is recommended, and is available in
convenient disc rolls.
Tech Tip: When using a random orbital sander it is best to start the disc flat on the workpiece to avoid gouging.
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