What Is the Grit Sequence and What Do I Need To Know?
What Is the Grit Sequence and What Do I Need To Know?
What Is the Grit Sequence?
In this article, you will be taught everything there is to know about the abrasives grit numbers and how you should use them. Using the right grit sequence is important to know to achieve the best finish on your workpiece. Using grit sizes that are not meant for certain applications can lead to problems and a bad end result.
What Are the Grit Sizes?
Generally, on the back of sandpaper – whether it is a sanding disc or a sanding belt – you will find a grit number. For example, the 80 grit abrasive will have ‘P80’ on the back of it. For starters, the lower numbers are the coarsest and as the number gets larger, the more fine they will be. Grit sizes range from coarse, medium, fine, very fine, and ultra fine.
Grit Sizes Further Explained
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Coarse Grits P24 P36 P40 P50 P60 P80 |
Medium Grits P100 P120 P150 P180 P220 |
Fine Grits P240 P280 P320 P360 P400 P600 and up. |
What Grit Size Should I use?
The grit size you use completely depends on the project you are working on. For heavy stock removal, coarser grits will be ideal, whereas higher grit sizes are better for finishing. If you need to use a sequence of grits for your workpiece, it is important to remember one thing. That one thing is Never Skip More Than One Grit. If you are confused by this, you can go from 100 grit to 150 grit (skipping 120 grit), but you cannot go from 100 grit to 180 grit (which would be skipping two grits – 100 and 120).
Why Should I Never Skip More Than One Grit?
For starters, skipping more than one grit size can ultimately shorten the lifespan of the given sanding belt or disc. It also will cause more damage than good giving the surface of your workpiece deep scratches and imperfections that can be very hard to get out. Not only will it leave deep scratches, but it will also give a blotchy and uneven finish with many swirls.
Essentially, each grit number is made to remove a certain amount of stock or give a certain finish. You may feel like following the grit sequence will take ages to finish; however, it is the opposite because skipping more than one grit will lead to damage that will take even longer to get out. Sanding the proper way will give you an even scratch pattern ensuring you happiness.
What Grit Size Should I Use For Sanding (continued) ?
So, we have gone over the different grits and the grit sequence, but you are still unsure which one you should be using. First lets go over the different applications you can use with the variety of grit numbers.
- The coarsest grits (P40 - P60) are used for applications such as removing bumps, old paint or finishes, and heavy stock.
- The grit size P80 will remove scratches and burns. P80 is the starting grit for most hardwoods, whereas P120 is the starting grit for softwoods.
- P150 will help prep for enamel paints.
- The grit size P180 will prepare for acrylics, along with helping with smoothing a surface and raised wood grain.
- P220 is going to be good for prepping for a wood stain and surface finishing.
- The grit size P320 is ideal for sanding in between coats or for wet sanding.
- P400 will be your final surface finishing grit. It can also prepare for finishing oils or smoothing out top coats.
- Finally, grit sizes P600 and above will prepare for polishing and fine wet sanding. It's great for using these applications on metals and plastics.
Now, let’s ask ourselves some questions that can help determine what grit size we may need. For example, you can ask what stage or step you are at in the sanding process, whether it is leveling out a surface, preparing for finishing, fine sanding, sanding in between coats, etc. Another good question may be how much stock you need to remove from your workpiece. You can also analyze what material you are working with – hardwood, softwood, metals, etc. Lastly, what tool you are using can be a great factor as well (or hand sanding).
What Sandpaper Grits Should I Use for Different Material or Applications?
If you are working with solid wood, the first grit size you should use should be P100 or coarser. As you move to a finer grit, avoid using too much pressure or stock removal to avoid an uneven surface. The last grit size you should use should not exceed P240.
For prepping a painted surface, stick to a grit material of silicon carbide. Use P240 or P280 as your last grit size for a great end result and finish.
Lacquer sanding should use a soft pad or contact roller after checking that the graphite is not damaged. Aluminum oxide is suggested in this application in order to cut the surface with ease. Avoid using a high sanding speed or too much pressure.