Grit Selection

Grit Selection

Grit selection tutorial covers choosing the proper sand paper grit when sanding cars, trucks, boats, and many other metal or fiberglass items.

 

by Gary Kinsey
Gary Kinsey has been a salesman for R&E Paint Supply for the last 12 years. He has a very proficient knowledge of the PBE industry and is a well trained customer service representative.
R&E Paint Supply
57 Avalon Lane
MT Home, Ar. 72653
1-800-316-6595
Abrasive Grit Selection:24 – 80 Grit – is used for stripping paints and undercoats off metal
surfaces. These grits can also be used for grinding spot welds,
removing heavy surface rust and leveling out plastic body filler. In
fiberglass repair these grits would be used for quick removal of excess
fiberglass, body filler, and roughing up the surface for a repair. These grits
may come in many different designs and cuts of paper. Just to name a few:
3″, 5″, 6″, & 8″ D.A. (dual action) sandpaper, 2-3/4″ x
16″, & 2-3/4″ x 17 1/2″ Longboard paper, 5″, 7″, & 9
1/8″ Fiber discs, and 2″ & 3″ Roloc or speed lock discs. There are
many other applications and designs but these are the most popular in
automotive and marine applications.100 – 180 Grit – is used for stripping paints and undercoats off metal
surfaces, feathering out old paint and primer finishes, and smoothing out
plastic body filler. These grits may come in many different designs and
cuts of paper. Just to name a few: 3″, 5″, 6″, & 8″
D.A. (dual action) sandpaper, 2-3/4″ x 16″, & 2-3/4″ x 17 1/2″ Longboard paper, and 9″ x 11″ WetorDry sheet paper, and standard 9″ x 11″ dry sanding paper. Each abrasive manufacturer offers several different attachment systems. There are many other applications and designs but these are the most popular in automotive and marine applications.

220 – 320 Grit – is used for feathering out old finishes, smoothing
out plastic body fillers, leveling primer surfacers, and stripping paint off
plastic or rubber parts. These grits may come in many different designs and
cuts of paper. Just to name a few: 3″, 5″, 6″, & 8″
D.A. (dual action) sandpaper, 2-3/4″ x 45 yds., & 2-3/4″ x 17 1/2″ Longboard paper, and 9″ x 11″ WetorDry sheet paper, and standard 9″ x 11″ dry sanding paper. Each abrasive manufacturer offers several different attachment systems. There are many other applications and designs but these are the most popular in automotive and marine applications.

360 – 400 Grit – is used for blocking.( Blocking is a term used
for the process in which the primer surfacer or the finish is sanded with a
flat block. (usually 6″ to 36″ long) in a crisscross pattern. When sanding, pull the block one direction about 4-6 passes then pull across in the opposite direction 4-6 passes in an X pattern. This will give you a flat surface. If you sand in an — inline pattern it will tend to dig a groove into the primer and result in a wavy finish when painted.) These can also be used to sand plastics and urethane bumpers prior to refinishing. These grits may come in many different designs and cuts of paper. Just to name a few: 3″, 5″, 6″, & 8″ D.A. (dual action) sandpaper, 2-3/4″ x 45 yds., & 2-3/4″ x 17 1/2″ Longboard paper, and 9″ x 11″ WetorDry sheet paper, and standard 9″ x 11″ dry sanding paper. Each abrasive manufacturer offers several different attachment systems. There are many other applications and designs but these are the most popular in automotive and marine applications.

600 – 800 Grit – is used to finish sand primer and older OEM finishes
that will be repainted. These grits aren’t usually used for blocking
(for meaning of blocking look at the section 360 – 400 Grit). The main purpose of these are to sand out the scratches that are left behind after using a coarser grit paper. These grits may come in many different designs and cuts of paper. Just to name a few: 3″, 5″, 6″, & 8″ D.A. (dual action) sandpaper and 9″ x 11″ WetorDry sheet paper, and standard 9″ x 11″ dry sanding paper. Each abrasive manufacturer offers several different attachment systems. There are many other applications and designs but these are the most popular in automotive and marine applications.

1000 – 1200 Grit – is used for blocking out runs, dirt and bugs out of
clearcoat. (Blocking is a term used for the process in which the clear coat
is sanded with a flat block. (usually 6″ to 36″ long) in a crisscross pattern. When sanding, pull the block one direction about 4-6 passes then pull across in the opposite direction 4-6 passes in an X pattern. This will give you a flat surface. If you sand in an —- inline pattern it will tend to dig a groove into the clear and result in a wavy finish.) These grits may come in many different designs and cuts of paper. Just to name a few: 3″, 5″, 6″, & 8″ D.A. (dual action) sandpaper and 9″ x 11″ WetorDry or 5-1/2″ x 9″ WetorDry sheet paper. Each abrasive manufacturer offers several different attachment systems. There are many other applications and designs but these are the most popular in automotive and marine applications.

1500 – 4000 Grit – is used for sanding or polishing out dirt, runs, orange peel, bugs and other imperfections in the finish clearcoat. These grits may come in many different designs and cuts of paper. Just to name a few: 3″, 5″, 6″, & 8″ D.A. (dual action) sandpaper, 1-3/8″ Finessing discs, and 9″ x 11″ Wet or Dry or 5-1/2″ x 9″ Wet or Dry sheet paper. Each abrasive manufacturer offers several different attachment systems. There are many other applications and designs but these are the most popular in automotive and marine applications. I hope this will be of assistance when selecting the correct grit for sanding.

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