Sander Guide

Complete reference for random orbital, belt, sheet, and detail sanders. Learn grit selection, proper technique, finish preparation, and how to avoid common sanding mistakes.

Sander Types

Random Orbital Sander (ROS)

  • 5" or 6" round pad spins AND orbits
  • Random pattern prevents swirl marks
  • Best all-around sander for most projects
  • Variable speed for different materials/grits
  • Hook-and-loop or PSA disc attachment
  • Best for: general sanding, finish prep, between coats

Belt Sander

  • Aggressive material removal
  • Common sizes: 3x21", 3x24", 4x24"
  • Keep it moving - can quickly gouge
  • Sand with the grain only
  • Best for: leveling, stripping finishes, rough work

Sheet/Palm/Finishing Sander

  • Uses 1/4 or 1/3 standard sandpaper sheets
  • Vibrating (orbital) action
  • Less aggressive, finer finish
  • Corners can reach edges better than round pads
  • Best for: light sanding, fine finish work, tight spaces

Detail/Corner Sander

  • Triangular pad reaches into corners
  • Oscillating action
  • Small surface area for detail work
  • Best for: furniture detail, moldings, window sashes
Sandpaper Grit Guide
Grit RangeClassificationBest For
40-60CoarseHeavy material removal, paint stripping
80Medium-coarseShaping, removing mill marks
100-120MediumGeneral smoothing, scratch removal
150-180FinePre-paint/stain preparation
220Very fineBetween finish coats, final prep
320-400Extra finePolishing, between finish coats

The Rule: Never skip more than one grit

Jumping from 80 to 180 leaves deep scratches. Progress: 80 → 120 → 150 → 180

Grit Progression by Finish Type
Finish TypeFinal GritNotes
Paint (latex/oil)150Paint hides minor scratches
Oil-based stain180Higher shows through stain
Water-based stain180-220Raises grain less if higher
Polyurethane/lacquer180-220Sand between coats at 220-320
Danish oil/tung oil220-320Shows every flaw, go higher
Sanding Technique

Basic Rules

  • Sand with the grain: Especially important at final grits
  • Let the sander do the work: Light pressure, don't push down
  • Keep it moving: Don't dwell in one spot
  • Overlap passes: About 1/3 to 1/2 overlap

Speed Settings (Random Orbital)

  • Low speed: Fine grits, finish sanding
  • Medium: General sanding, most work
  • High: Coarse grits, heavy material removal

Belt Sander Specifics

  • Always sand with the grain direction
  • Start sander before contacting wood
  • Keep it moving - never stop while running
  • Use both hands for control
  • Can create flat spots if you pause
Avoiding Common Mistakes

Swirl Marks (Random Orbital)

  • Caused by too much pressure
  • Moving too fast across surface
  • Worn or loaded sandpaper
  • Solution: light pressure, slow movements, fresh paper

Gouges (Belt Sander)

  • Stopping while sander is running
  • Tilting to one side
  • Solution: keep moving, keep flat

Cross-Grain Scratches

  • Sanding perpendicular to grain
  • Shows prominently under stain
  • Solution: final passes always with the grain

Uneven Surface

  • Sanding edges more than middle
  • Not covering entire surface evenly
  • Solution: systematic coverage, check with side lighting
Sandpaper Types

Attachment Methods

  • Hook-and-loop: Velcro-like, easy change, reusable
  • PSA (Pressure Sensitive Adhesive): Peel-and-stick, often cheaper
  • Match to your sander's pad type

Abrasive Materials

  • Aluminum oxide: Most common, good all-around
  • Silicon carbide: Sharper, for finishing, wet sanding
  • Ceramic: Longest lasting, hardwoods, aggressive
  • Zirconia: Heavy-duty, metal and hardwood

When to Change Paper

  • Paper is torn or worn through
  • Surface becomes glazed/shiny
  • Sanding takes noticeably longer
  • Paper is clogged with dust (use dust collection)
Safety & Best Practices

Required PPE

  • Dust mask/respirator: Fine dust is harmful
  • Safety glasses: Particles can fly up
  • Hearing protection: Prolonged use causes damage

Dust Collection

  • Use sander's built-in collection when possible
  • Connect to shop vac for better extraction
  • Use dust collection discs (holes match pad)
  • Some wood dusts are toxic (walnut, cedar)

Workpiece Security

  • Clamp work securely for belt sanding
  • Use non-slip pad for ROS on light pieces
  • Sand toward clamps, not away

Additional Information

About This Sander Guide

Proper sanding is the difference between a professional-looking finish and a disappointing one. Surface preparation accounts for most of the final appearance - a flawless finish cannot hide poor sanding, but excellent sanding makes any finish look better.

Understanding grit progression is fundamental. Skipping grits leaves scratches that show up prominently under stain or clear finishes. The right final grit depends on your finish type - paint hides more than penetrating oil. Taking the time to progress through grits properly saves rework later.

The random orbital sander has become the go-to tool for most sanding because its random pattern prevents the swirl marks that plague other sanders. For aggressive stock removal, a belt sander still excels. Detail sanders handle spots the others can't reach.

Why Use This Reference Guide?

Quick reference for grit selection and technique helps achieve better finishes with less effort.

  • Select the right sander type for each job
  • Understand grit progression for different finishes
  • Avoid swirl marks, gouges, and scratches
  • Use proper technique for each sander type
  • Know when to change sandpaper
  • Work safely with dust protection
Frequently Asked Questions

Free Sander Guide - Random Orbital, Belt & Sheet Sanders with Grit Selection | DIYProject.ai