Choosing the right sandpaper grit is crucial for achieving the desired finish on your DIY or woodworking project. The grit number refers to the size of the abrasive particles on the sandpaper, which determines how coarse or fine it is. Selecting the proper sandpaper grit will ensure efficient material removal and a smooth sanded surface. This comprehensive guide will teach you everything you need to know about choosing sandpaper grit.

Understanding Sandpaper Grits

Sandpaper grit is denoted by a number that indicates the quantity of abrasive particles per square inch of sandpaper. The lower the grit number, the coarser and more abrasive the sandpaper. Higher grit numbers denote finer abrasive particles that produce smoother finishes.

Here is an overview of different sandpaper grit sizes:

Extra-coarse (24-40 grit): Used for rapid stock removal, like grinding or shaping wood. Leaves deep scratches.
Coarse (50-80 grit): Quickly removes material and evens surfaces. Leaves visible scratches.
Medium (100-120 grit): Removes scratches left by coarse paper. Leaves slight scratch marks.
Fine (150-220 grit): Smooths surface and eliminates scratch marks for a polished finish.
Extra-fine (240+ grit): Used as final sanding stage before finishing/painting. Produces ultra-smooth surface.

So in summary, lower grits aggressively remove material, while higher grits smooth and polish the surface. Matching the right grit to your application and sanding needs is key.

Factors for Choosing Sandpaper Grit

Consider these key factors when selecting sandpaper grits for your project:

1. Material Being Sanded

Wood: Start with 80-100 grit for rough wood, then progress to 120, 150 and 220+ grits. Softer woods may only need 150-220 grit for final smoothing.
Metal: Start with 80-120 grit to remove oxidation and imperfections. Move up to 150-220 grit for smoother finish.
Drywall: Begin with 100-150 grit, then finish with 220 grit for smooth walls before painting.
Concrete: Use 60-80 grit to remove layers and smoothen surfaces. Finish with 100-150 grit.

2. Amount of Material Removal Needed

For heavy sanding/removal, use coarser 40-80 grit.
For lighter sanding, begin with 100-150 grit.
Finer 220+ grit is for final smoothing without scratch marks.

3. Desired Surface Finish

Lower grit leaves visibly scratched surface.
Medium grit provides smooth finish with minor marks.
Higher grit gives polished, ultra-fine finish.

4. Manual vs Machine Sanding

Coarser grits up to 100 can be used for hand sanding.
For machine sanding, avoid low grits and start with 120 or higher.

5. Sandpaper’s Open Coat vs Closed Coat

Open coat allows debris removal and works for high material removal.
Closed coat sandpaper clogs less and gives smoother finish on final sanding.

Considering these factors will help narrow down ideal grits for your application.

Sandpaper Grit Progression for Best Results

It’s best to start sanding with a lower grit to remove bulk material, then gradually step up to finer grits to eliminate scratches and polish the surface. Here are some examples of effective grit progressions:

Sanding Raw Wood

80-100 grit to flatten surface
100-120 grit to remove coarse scratches
150-180 grit for a smooth finish
220 grit for final sanding before finishing

Sanding Wood for Stain/Paint

100-120 grit to flatten and remove imperfections
150-180 grit to smooth surface
220-320 grit for ultra-fine finish before coating

Sanding Metal

80-120 grit to remove rust and flaws
150 grit to smooth out coarse scratches
220-320 grit for polished metal surface

Sanding Drywall

120-150 grit to level surface
220 grit to eliminate scratches and dust before painting

Follow this multi-step grit progression for best results on all materials. Jumping grits or skipping steps can lead to wavy finishes or deep scratches.

Matching Sandpaper Grit to Power Sanders

If using power sanders, match the sandpaper grit to the sander’s abilities:

Belt sanders: Ideal for 24-80 grit heavy stock removal on wood.
Orbital sanders: Well-suited for 80-220 grit sanding on wood/metal. Great for smoothing and final sanding.
Sheet/disc sanders: Use higher grits like 150-320 when possible to avoid swirl marks.
Detail/palm sanders: Excellent for precision sanding with 150-400 grit papers.

Consult your sander’s manual on recommended grits. Using very coarse paper on high-speed sanders can damage surfaces.

Hand Sanding vs Machine Sanding

Hand sanding with sandpaper blocks gives you more control over sanding direction and pressure. Start with 100-150 grit for hand sanding, as coarser grits are too aggressive.

Power sanders speed up the process considerably. Let the machine do the work using the appropriate grits. Use lighter pressure and frequently clean/replace sandpaper.

Hand sanding excels at detailed work on edges, curves and hard-to-reach areas. Machine sanding quickly smooths large flat surfaces. Use them together for best results.

Wet Sanding vs Dry Sanding

Wet sanding is done using water or another liquid lubricant to create a slurry. The water helps keep sandpaper clean and prevent clogging. Wet sanding also reduces airborne dust.

Begin by dry sanding with coarser grits for stock removal. Then wet sand with higher 220+ grits to prevent scratches when smoothing. Some benefits of wet sanding:

Reduces sanding marks and scratches
Gives very smooth glossy finish
Keeps sandpaper unclogged for longer
Minimizes airborne dust

The downsides are added mess and needing to dry the surface after wet sanding before finishing/coating. Dry sanding is simpler for quick jobs.

Identifying Sandpaper Grit by Color

Not sure what grit your sandpaper is? Most manufacturers color code sandpaper to indicate the grit grade:

Brown – Very coarse (24-36 grit)
Dark green – Coarse (46-60 grit)
Blue – Medium (80-100 grit)
Red – Fine (120-150 grit)
Yellow – Very fine (180-220 grit)
White – Extra fine (240-600 grit)

Check the sandpaper’s back or edge for the color coding, which should match the grade printed on the sheet.

Sanding Techniques for Each Grit

Proper sanding techniques are also important for achieving the best result:

Coarse grits: Aggressively sand back and forth along the wood grain to remove material rapidly.
Medium grits: Use lighter pressure and gentler motion diagonally across grain to smooth surface.
Fine grits: Sand in small circular motions to blend and polish surface without new scratches.
Extra-fine grits: Use very light pressure and small movements to gently buff surface to glossy finish.

Adjusting your hand sanding technique will help utilize each grit most efficiently. Let the sandpaper do the cutting – don’t press too hard.

Common Sandpaper Grits for Woodworking

Here are some commonly used sandpaper grit recommendations for key woodworking applications:

Stripping paint/varnish: 40-80 grit removes old coatings rapidly from wood.
Sanding rough lumber: 80-120 grit levels boards and eliminates mill marks.
Smoothing planed boards: 120-180 grit finishes wood ready for staining.
Sanding between coats: 220-320 grit abrades just enough for next coating layer.
Fine wood finishing: 320-400 grit gives ultra-smooth sanded look before oil/wax.
Polishing: 600-2000 grit wet sanding achieves highly reflective surface.

Match your purpose to the ideal grit range for the task for best efficiency.

Tips for Choosing Sandpaper Grit

Keep these tips in mind when selecting sandpaper grits:

Finer isn’t always better – start coarse if you need to remove a lot of material.
Read sandpaper packaging closely to identify the grit grade.
Progress through at least 3-4 grits from low to high for best finish.
Replace sandpaper frequently as it wears out quickly.
Consider the final desired look – coarse grit leaves visible scratch pattern.
Wet sanding with high grits minimizes fine swirl marks and scratches.
Don’t skip grits to save time – you may end up having to go back and do more sanding.
When in doubt, start a little coarser and step down grits until surface is smoothed.

Choosing the right sandpaper grit takes some experience, but following these best practices will help you achieve better sanding results on your projects.

Frequently Asked Questions

Should I start with coarse or fine sandpaper grit?

It’s best to start coarse if you need to flatten, smooth out defects or do heavy stock removal. Begin with 60-100 grit to rapidly sand down the surface, then work up to finer 180-220 grit papers for smoothing and polishing the finish.

How do I know if my sandpaper grit is worn out?

Check sandpaper frequently as it wears quickly. Signs of dull, worn out sandpaper include lack of abrasion, burn marks on the surface, clogging of the paper with debris and fraying of the backing. Replace worn sheets for optimal sanding.

How fine of grit sandpaper should I use before painting or staining wood?

Before applying paint or stain, sand wood with 150-220 grit sandpaper for best results. This smoothes the wood properly so the coating adheres well and looks even. Extra-fine 320+ grit may make stain absorption uneven.

What grit should I use when sanding between coats of polyurethane or varnish?

Lightly sand between finish coats using 320-400 grit sandpaper. This allows the next coat to bond well without abrading too much of the previous layer. Take care not to cut through the prior coat.

Is it bad to skip sandpaper grits and go from coarse to fine?

Skipping grits can leave deeper scratch marks that are harder to remove, since each jump leaves progressively finer scratches. Gradually stepping down grits ensures an even scratch pattern for the smoothest possible finish.

How can I avoid swirl marks when machine sanding?

Use a high enough grit like 150+ with power sanders, apply light pressure, and frequently change sandpaper to minimize swirls. Also, try wet sanding – water lubrication prevents fine circular scratches. Hand sanding with the wood grain helps too.

Conclusion

Sandpaper grit selection plays a major role in achieving the desired outcome when smoothing, refinishing or polishing a surface. Considering the abrasion needs, the material, desired final look and using proper grit progression will ensure high-quality results and save rework. Mastering the nuances of different sandpaper grits takes some experience, but the payoff is a beautifully sanded project. Match your purpose and materials to the right sandpapers for superior outcomes.

How to Choose Sandpaper Grit

Choosing the ideal sandpaper grit is key for properly sanding down surfaces. Selecting the right grit grade involves understanding sandpaper abrasiveness, your project needs, sanding techniques and grit progression. This guide will teach you how to choose sandpaper grit for optimal results.

Follow this process to select suitable sandpaper grit:

1. Determine Abrasiveness Needed

Consider how much material you need to remove:

For heavy sanding, use extra-coarse 24-40 grit
For moderately coarse finish, opt for 50-80 grit
To smooth existing surface, choose fine 120-220 grit
For final precision polishing, use extra-fine 280-600 grit

2. Consider the Work Material

Match grit to the workpiece for ideal results:

Wood: 60-220 grit range
Metal: 80-320 grit range
Concrete: 60-150 grit range
Drywall: 100-220 grit range

3. Pick Grits for Desired Final Result

Lower grits leave visibly scratched surfaces, while higher grits create polished finishes:

Coarse look: 60-100 grit
Smooth look: 120-180 grit
Glossy look: 220-400+ grit

4. Hand Sanding vs Machine Sanding

For hand sanding, use 100-220 grit
Machine sanding allows higher 80-320 grit range

5. Grade Grits Properly

Start low and step up grits progressively (e.g. 80, 120, 150, 220)
Don’t skip more than 1-2 grit grades when progressing

Following these simple factors will help you select sandpaper with the ideal abrasiveness and grit rating for your application. Reference the color-coded grit system and match sandpapers to your purpose for the best outcome. Proper grit selection is key to efficient, quality sanding.

How to Choose Sandpaper Grit

Choosing the right sandpaper grit is crucial for properly sanding wood, metal, concrete and other materials. Here are some best practices for selecting ideal grits to achieve a smooth sanded surface:

Understand Grit Grades

Lower grit = more coarse abrasion
Higher grit = finer polishing abrasion
Grit refers to the abrasive particles per square inch in the paper.

Match Grit to Purpose

Wood stripping: 40-60 grit removes old finish
Stock removal: 80-100 grit for fast shaping
Smoothing: 120-150 grit eliminates scratches
Finishing: 220-400 grit for ultra-fine sanding

Select Grits Based on Material

Softwood: 100-220 grit range
Hardwood: 80-180 grit range
Metal: 80-320 grit range
Drywall: 120-220 grit range

Use Proper Grit Progression

Start with coarser grit
Step up to finer grits progressively
Example: 80 > 120 > 180 > 220 grit

Consider Sanding Method

Hand sanding: 100-220 grit ideal
Machine sanding: 80-320 grit works better

Choosing sandpaper grit is easier when you consider your abrasion needs, material, finishing goals and sanding method. Understanding grit grades, using proper progression and matching grit to purpose will achieve the best results.

Conclusion

Choosing the ideal sandpaper grit is a crucial step for any sanding project. With a wide range of abrasive grades available, it may seem daunting to select the right sandpaper for your specific application. However, by understanding key factors like your desired finish, amount of stock removal required, work material characteristics, manual vs machine sanding, and proper grit progression, you can determine the optimal grits that will provide an efficient process and superior result.

Whether you need aggressive coarse sanding to shape and smooth a rough surface, or fine polishing abrasives to create a blemish-free luster, the tips provided in this guide will help match you to the perfect grit. While it may take some trial and error to refine your grit selection skills, the time invested will pay off with beautifully sanded projects that meet your vision. So apply these lessons, get hands-on practice, and ensure you have the ideal sandpaper on hand for every sanding task.