Everyone has used sheet-size sandpaper at least once, right?
Sheet-size sandpaper is easily available at home centers, and it is such a commonly used abrasive that it is even employed in elementary school arts and crafts classes.

In fact, the dimensions of such sandpapers are often the same, even if they are made by different manufacturers.

Why on earth?

We use them all the time, but we don't always know why.

In this issue, we will explain the surprisingly unknown size of sandpaper.

1. How many mm of sandpaper size？

The dimensions of the sheet size sandpaper are 230 mm x 280 mm.
The size of a typical A4 copy paper is 210mm x 297mm, so the shape is slightly longer horizontally and shorter vertically than that.

Where did this unique size come from?

2. Is it true that there is a standard for the size of sandpaper?

In fact, the size of sandpaper is precisely defined by JIS.
According to JIS R6252, "5. Dimensions and dimensional tolerances" of abrasive paper, there are six different sizes defined for sheets other than 230mm x 280mm.
In addition, both width and length are finely defined with a tolerance of ±3 mm.

reference：https://kikakurui.com/r6/R6252-2006-01.html

This JIS R6252 is a unique standard for abrasive paper, so it differs from the dimensional standards for copy paper and other common paper.
Still, 230 mm x 280 mm seems a bit of a halfway figure.
Wouldn't it have been better to use 250mm, which is a good cut-off, don't you feel?
But there are historical reasons for this as well.
In the past, the size of sandpaper was defined as 9inch x 11inch, using the yard-pound unit of measurement called inch.
Later, with the transition to the metric system, it was converted to its current size of 230 mm x 280 mm.
Indeed, 1inch is 25.4mm, so 9inch x 11inch, when converted back to the metric system, becomes 228.6mm x 279.4mm. This is the origin of the sheet size sandpaper dimensions of 230mm x 280mm.

In this issue, we have introduced some trivia about abrasives that you may or may not know.
Many of you may be surprised that there are standards for the dimensions of abrasive materials.

If you are interested in abrasive materials, please feel free to contact Sankyo Rikagaku.