Abrasive Grit Grades – Explained
Everything You Need To Know About Abrasive Grit & Grading
what do the numbers mean on the back of sanding sheets and what does the ‘P’ stand for?
A common question asked by many, and this blog post will not only answer that question but also give a slightly more in-depth explanation into abrasive grading and grit size.
What do the numbers mean?
As you may already know, the higher the grit number, the finer the abrasive product. This is due to the grit size of an abrasive sheet being the number of sharp particles per square inch of sandpaper. And from the grit size, we get the abrasive grade. This is an indicator of how coarse/fine the sandpaper is and what its grit is in the range of.
So, a larger grit number indicates a smaller abrasive grain and a finer abrasive product.
A “P” in front of the grit size indicates that the product is graded in accordance with the European FEPA standard. You should always look for products with a P in front of the grit size as being measured by this standard ensures for an accurate number and a smooth sanding.
Indication of Use
The terms coarse, medium and fine are often used in conjunction with grit size of abrasive grains. They range from 40 (very coarse) to over 400 (very fine). Good quality sandpaper will have universal sized grit. The size of grit is used to classify the sandpaper by ‘grade’ as follows:
Individual abrasive strips and discs are usually marked on the paper / hook & loops reverse with the grit size (e.g. 100) and/or with the grade (e.g. medium coarse). Grit sizes above 240 are classed as “very fine” and are commonly used for significantly harder, fine surfaces that require special considerations taken to the surface.
Which Grade To Use?
For maximum stock removal when sanding, start with a low grit abrasive (Coarse Graded). Choose the exact grit based on the condition of your wood and work up until you achieve the finish you require. Remember though, you don’t have to use every grit as you go from coarse to fine
For finer work and finishing wood, you’ll need to use a Fine graded abrasive such as 150 grit on open grain wood or 180 on closed. For oil finishes it is best to use even higher up to 240 grit.
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