October 26, 2020 4 min read

Choosing Grit Sequence

Quick Summary

Generally speaking, you’ll want to use coarse grits (P8 - P80) for stock removal and the stripping of paints and varnishes. You’ll then want to use medium grits (P100 - P220) for prepping and shaping materials followed by fine grits (P240+) for sharpening and polishing.

Topics Covered

During a sanding project, choosing the right grit sequence is critical. You want to start with a rougher abrasive that eliminates all stock and finish, followed by successively finer grits that clear away sanding marks until a smooth finish results. Any deviations can compromise the quality of the finished workpiece, so the team at Red Label Abrasives has put together this sanding grit guide to support the success of your sanding efforts.

Grit sizes explained

Coated abrasives like sanding belts, discs, rolls, and sheets have a range of grain sizes. At Red Label Abrasives, our products use theFederation of European Producers of Abrasives (FEPA) standard, which means that the grit is signified by the letter P and a number, such as P80 or P240. The lowest numbers denote the coarsest grains while finer ones have a high number.

The number of grit sizes that you’ll need to keep in stock will depend on what you work on. Are you a hobbyist or professional knifemaker? Do you make rough, handcrafted furniture or try to get sheet metal as smooth as glass? Red Label Abrasives can advise you on which grits you should have on hand for best results.

What does a good grit sequence look like?

If your process starts with rough sanding and ends with a flawless finish, you should never bypass more than one grit. For example, if you use a P80 to strip away caked-on, layered paint and follow it with a P180 instead of P120 or 150, the marks from the paint removal won’t totally be removed. You’ll end up oversanding and create an uneven finish or sanding swirls.

Why does this happen? When you start with the coarsest grit, you apply deep scratches on the workpiece surface. By using a correct grit sequence, you gradually even out the scratches. When you skip more than one grit, the higher grits only cut the tops of the scratch peaks, leading to an uneven pattern and blotching.

How to choose the right sequence 

When determining the right grit sequence for your application, confirm what you want to achieve. How much material needs to be removed from the workpiece? What material are you working with? (For example, metal vs. a soft wood like pine.) Does the finish need to be glass-smooth or are you looking for a more textured effect?

Below is an overview of common grit numbers and their recommended applications:

  • P40-P60: For stripping finishes and paints, smoothing rough pieces of lumber, removing stock from thicker pieces of metal, or removing knots or bumps in wood pieces.
  • P80: This is the recommended starting grit for working with hardwoods. It also does an effective job of removing shallow scratches from metal surfaces.
  • P120: Recommended starting grit for softwood sanding.
  • P180: Smoothing surface irregularities and raised wood grains.
  • P220: Appropriate for wood stain preparation or commencing surface finishing.
  • P320: Wet sanding or sanding between coats. (Be sure to use an abrasive that’s compatible with wet applications.)
  • P400: This grit does a good job of preparing a surface for finishing oils or smoothing top coats. It is also used as a finishing grit for many materials. 
  • P600 and up: Any grit above the 600 range is recommended for plastics and metals, fine wet sanding, or preparing a surface for polishing. Abrasives scratch metal far easier than they scratch wood. Scratch marks also aren’t as easy to remove from metal as they are from wood. Therefore, fine to ultra-fine grits from 600 to 1,200 are most useful when polishing metal. 

The information above has also been condensed in the chart below for our comprehensiveAbrasives 101 guide.

 

Category

Grit Range

Uses

Coarse

P8 - P80

  • Stock removal
  • Stripping of paints, varnishes, etc.

Medium 

P100 - P220

  • Prepping materials for paints, stains, etc.
  • Final shaping
  • Removal of planning marks
  • Honing 
  • Sharpening

Fine

P240 +

  • Sharpening
  • Polishing

 

Selecting the right grain material is just as important as creating an appropriate sequence. At Red Label Abrasives, we supply the following abrasive materials:

  • Aluminum oxide: One of the most popular and affordable options, aluminum oxide is highly friable, meaning that it fragments during use to provide a consistently sharp cutting edge. If you strip and finish wood or want to grind metals, there are open and closed coat versions for your application.
  • Silicon carbide: This specialty abrasive is frequently used for finish work because of its consistent cut rate. Its ability to sand material without a lot of heat buildup makes it an ideal option for finishing heat-sensitive applications like resinous wood.
  • Ceramic: A premium abrasive grain,ceramic has the longest lifespan of any abrasive material. It cuts energetically through hard woods and metal, its high friability delivering a consistently sharp cutting surface.
  • Zirconia: Before ceramic was used, zirconia was the go-to abrasive for durable and aggressive cutting performance. It is still a recommended option for stripping hardwoods and metal grinding and polishing.

Contact an Abrasive Specialist

Choosing the right grit sequence (and the right grit) is essential to a successful outcome. The basic guidelines in this blog can get you started, but if you are new to working with certain materials or have questions about how to get the best result for a particular application,Red Label Abrasives is here to help and provide you with the abrasive knowledge and materials you need. 

All of our abrasives are custom-manufactured for premium quality without the premium price. We are a family-owned manufacturer and take great pride in offering exceptional customer support with unrivaled technical support. You can reach out to us anytime by calling (844) 824-1956 or filling out acontact form.