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When it comes to auto body repair or metalworking, one tool shows up in every stage of the job—from surface prep to finishing touches: wet dry sandpaper sheets. Their versatility, durability, and ability to be used with or without water make them a must-have for professionals and DIYers. But getting the results you want depends heavily on one thing: choosing the right grit.
In this guide, we’ll break down how grit numbers work, which grits to use at each stage of a project, and how to avoid common sanding mistakes.
Wet dry sandpaper is usually made with silicon carbide, a hard abrasive that performs well on metal, paint, and plastic. It can be used dry for rapid material removal or wet to reduce clogging, minimize dust, and produce a smoother finish.
Using it wet also helps cool the surface, which is especially important when working with car panels or thin sheet metal.
Grit refers to the size of the abrasive particles:
Low grit = coarse (fast cutting but rough finish)
High grit = fine (slow cutting but smooth finish)
For auto body and metalwork, the most common grits range from 80 to 3000.
Use these coarse grits when you need to:
• Strip old paint or rust
• Shape body filler
• Remove high spots on welded seams
Tip: 80-grit is aggressive—ideal for initial work but not for finishing.
These grits refine rough shaping and prep surfaces for primer.
150–180 grit: smoothing body filler after initial shaping
220–320 grit: feathering paint edges and preparing panels for primer
Using water at this stage isn’t necessary, but dry sanding speeds up the process.
After the filler is smooth and the panel is coated with primer:
• 400 grit is ideal for sanding primer surfacers
• 600 grit preps the surface for basecoat in modern paint systems
Wet sanding is recommended to prevent clogging and produce a uniform finish.
Fine grits ensure the paint adheres properly without scratches showing through.
• 800–1000 grit: dulling old clear coat before repainting
• 1200–1500 grit: leveling fresh clear coat before final buffing
Always use these grits wet for best results.
These ultra-fine grits are for refining minor imperfections such as:
• Orange peel
• Dust nibs
• Clear coat imperfections
Follow with a polishing compound for a high-gloss, mirror-like finish.
Metal projects often follow a similar grit progression, with some differences:
• Removing rust
• Deburring sharp edges
• Smoothing welds
• Refining scratch patterns
• Preparing metal for primer, coating, or bluing
• Polishing stainless steel
• Refining tool surfaces
• Achieving brushed or mirror finishes
Wet sanding reduces heat, which helps prevent warping thin sheet metal.
Too Coarse:
• Leaves deep scratches visible after painting
• Removes more material than needed
• Causes uneven surfaces or waves
Too Fine:
• Doesn’t cut efficiently—wastes time
• Fails to give primer or paint something to grip
• Can lead to poor adhesion and peeling
Following a correct grit progression prevents these issues.
• Always use sanding blocks on flat surfaces to prevent waves.
• Sand in alternating directions with each grit to see when scratches are fully removed.
• Keep the surface clean—grit particles can cause deep scratches.
• Use plenty of water during wet sanding to reduce friction and keep the paper from loading up.
• Don’t skip grits. Jumping from 80 to 400 will leave hidden scratches.
Selecting the right grit of wet dry sandpaper is essential for achieving a professional finish in auto body repair and metalwork. Start coarse, work progressively finer, and always match the grit to the stage of your project. With the right approach—and the right sandpaper—you’ll get smoother surfaces, better paint adhesion, and a flawless final finish.
