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How to Choose the Right Random Orbital Sander Size

Understanding Orbit Sizes for Random Orbital Sanders

To get quality results when sanding with a random orbital sander, choosing the optimal orbit pattern sizes is critical. In production environments where consistency and matching finishes across batches of parts, the way the sander creates the scratches (sanding) is of utmost importance. This article will break down each size and match it to the optimal sandpaper grit grade range it should be paired with. 


What does orbit size mean?

Put very simply, the orbit size is the size of the little circles (or ellipse) diameter as the orbital sander spins as it oscillates. Larger the smaller the size, the tighter the pattern the sander will make. Below is a visual representation of the path a single grain of abrasive will travel in one revolution of the pad. 


3/8 inch orbit

This is the most aggressive sanding pattern, most optimal when used with very coarse grades. Typical range for orbital sanding is 60-80 grit. This range and pattern are best suited for stock removal and dimensioning applications. Using finer grades with this large of a pattern will leave un-satisfactory finish results and large swirl marks.


3/16 inch orbit

This size is the most popular and prevalent as this is the most general or versatile orbit size. Grit range it is best suited for is 100-220 grit grade range, where most sanding happens. If you had to choose one orbit size, this would be the one to choose. The downside is the size is a little too small for coarse grades as the mineral size can be half the distance of the circle, meaning mineral is not covering as much area per revolution as it could. This means more time is needed to do the same amount of sanding with coarser grades.


3/32 inch orbit

This size is almost exclusively relegated for fine or ultra-fine sanding. Choose this size with the final finish is of utmost importance. Grit grade range is from 320 grit and finer, topping out somewhere around 2000 grit.

Finer than 2000 grit a slower speed polisher type tool with abrasive compounds and bonnets are used (depending on application)

The chart below can also be used as a guide to know what type of sanding you intend to do and help match that up with the correct orbit size and sander.


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