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A Thickness Sander Is An Awesome Tool To Own
This article links to a really detailed set of instructions on how to make the machine shown in the picture.
I use my small commercial sander mostly for a final smoothing pass to get rid of the marks that my planner leaves in wood pieces. That saves a lot of hand sanding.
Occasionally I use it to flatten and thickness wide boards. It works but can be a slow process.
A machine like this is a valuable addition to your shop.
If you would like to make your own go here for lots of construction pictures and instructions.
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