Customized shaped blocks are a must for properly sanding concave curves. They are a key player on the Tools for Curves team. Cork has the ideal flexibility and resiliency for backing the sandpaper.
Lately, I have been making the blocks entirely from cork. These work better and are easier to make than what I formerly used, which was shaped wooden blocks with a layer of cork added to the working surface. By the way, I have experimented with pink foam board insulation and found it difficult to shape reliably.
To make these all-cork blocks, you need thick stock. It is wonderfully easily to cut with a handsaw or bandsaw, and shape with a moderate-grain rasp. The curve does not always need to be a constant radius – simply draw it freehand and saw. Refine it with the rasp, ensuring that it is just a bit steeper than the steepest section of the work piece.
Make the thickness of the block to your liking based on how you want to grip the block. The block pictured at the top is about 1 1/2″ thick. You can try to size the block for optimal convenience in cutting the sandpaper from standard 9″x11″ sheets, and to minimize waste, but good function and feel in the hand are the more important factors for me.
Saw kerfs 3/4 -1″ long about 1/2″ from the top face of the block to house the ends of the sandpaper. Hand pressure will naturally keep the paper in place (see below) even in fine grits and more so in coarse grits. No wedges or clips are needed. The chamfers at the beginning of the slots toward the working face are important.
To install the sandpaper:
Enter one end just a little into the slot, then bring the other end around the block and push it almost all the way into its slot. Working back the other way, snug the paper around the block and then push the original end as far as possible into its slot. Make a final tightening of the paper by pressing the paper it against one of the chamfers then use your fingertips to goose the paper even more into the slot.
The simple design of these blocks along with this paper insertion procedure produce a tighter hold on the sandpaper against the surface of the block than any commercial curved block that I have used (none of which I like).
Finally, the light weight of an all-cork block is an asset not to be underestimated in the countless (ugh!) reciprocation of sanding work.
Find thick cork by searching online. Try “cork blocks” or “cork yoga blocks.” I suggest the Corkstore (Jelenik Cork Group), which currently sells a 9×5″x5″x3.5″ yoga block for $19.25, and 12″x8″x2″ block for $17.10. This is a nice fine grain cork that is easy to shape reliably. Dick’s Sporting Goods sells a 9″x4″x6″ block, so you might be able to find it locally.
