Automotive Business An Abrasive One To The Finish

By: The Auto Guy Email
By: The Auto Guy Email

Abrasives are used a lot in the automotive world, starting with sandpaper.

Sandpaper is classified by its grit with the amount of abrasives per square inch on the paper being the grit number. So a 36 grit piece of sandpaper is much rougher than a 320 grit sandpaper because those grit particles are much larger and rougher on the 36 grit paper.

Rough sanding discs like 36 grit are usually used to grind on sheet metal. While it removes a lot of material very quickly, it also leaves a very rough surface behind when it is done.

One-hundred-eighty to 320 grit sandpaper is more commonly used when body techs are smoothing out body filler or feather sanding paint. Many times they have a sticky back on them so the tech can simply stick it to the tool and start sanding. When a tech needs to be very precise with his sanding, he might hand sand with different types of sanding blocks. A basic block holds the sandpaper nice and flat while other types are molded to fit into curved areas or body lines.

Scuff pads are available in several abrasive levels and they are used to prepare unsanded items for painting. If we didn’t scuff those surfaces ahead of time, the paint products would not adhere to the parts. Sanding pads are more like a stiff sponge with an abrasive outside surface. These will contour to whatever surface they are being used on.

There are abrasive products that are designed like round Brillo pads and they fit into the end of a drill. As they spin on the drill, they remove paint in areas such as door edges without damaging the metal underneath.

Another similar product uses an abrasive that is like a pencil eraser and it scrubs tape residue off of panels with a similar spinning motion without damaging the paint.

Cut off wheels are composite abrasive discs that cut through metal at a high speed. The wheel is only about one-eighth-of-an-inch thick and it mounts in the end of a high speed grinder. Metal parts are no match for a tool like this.

Painters use the finest sandpaper in the shop. Prepping the vehicle for paint requires 320 to 800 grit sandpaper. Anything less than that would leave sand scratches in the paint surface when the job is done. After the paint cures, the painters use a special sandpaper that is designed to be used with water. This wet sandpaper starts at around 1000 grit and works its way all of the way up to 3000 grit. After wet sanding, rubbing compounds are used with buffers to get that paint perfectly smooth and shiny. The rubbing compounds also have abrasives in them to buff the finish to a perfect shine.

That describes some of the most common types of sanding and cutting materials we use in the shop and there are even more that I could talk about. But I won’t do that. I certainly don’t want to come across as being too “abrasive."

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