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designing and building with wood channels my creativity and challenges my mind.
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Saturday, May 14, 2011

DIY sanding block & Klingspor Sand Paper for Sand Flee

For final sanding and rubbing out a finish, a good sanding block is essential.  These final finishing steps require precision and flatness, and are always prone to accidental "cutting through" on the edges of a piece.  Power sanders are often too much tool, and anyway the final sanding and polishing should be done in a linear motion anyway.

For sanding of profiles, such as molding and flutes, a shop-made sanding block is the only way to get into tight curves and corners.

This post is about how to make sanding blocks for any purpose.  It includes tips from my experience on how to outfit a sanding block for perfect results that are nearly fool proof.

Sanding block shaping:
to make a sanding block for flat surfaces, I like to start with a piece of hardwood 1-2" thick, or two or three pieces of 3/4" voidless plywood stacked on top of each other.  I rip the block to between 2-3", depending on the size of the panel I'm sanding.  Length depends on the job, but my panel sanding blocks are between 5" and 10" long.
fig, 1 - A different profile on each edge, with built-in fences

For sanding profiles and flutes, cut the opposite profile in the block as you cut in your workpiece.  Sometimes, this is as simple as chucking a 1" roundover bit into your router, to match a 1" cove in your workpiece.  For sanding more complicated profiles, I put a different profile on each of the four edges of the sanding block, one for each segment of the more complicated profile on the work.  In this case,  it is always helpful to cut a mini "fence" into the edge of the block, so the block will align itself as it rides along the profile in the workpiece.

Sometimes, I have to sand a piece after I've assembled it, for example when repairing a blemish in the finish.  In these cases, it can be hard to get into corners.  To make it easier, I cut one end of the sanding block at 60 degrees on two faces, giving me a sharp point on one end.  It's easy to get all the way into corners with this setup.

But if you're going to be polishing a flat surface or sanding a frame and panel door, be sure to round over the edges of the sole on your sanding block.  That way, you won't catch an edge on the workpiece, gouging the finish.
the fence keeps the corner square while I sand


Sanding does change the dimensions of a workpiece.  Ideally, it makes the work a little thinner, and that's it.  But anybody who has sanded a piece of furniture knows, it's easy to make a mistake at any phase of sanding - from cutting through the finish, to scoring an ugly gash in an otherwise pristine edge.  As a novice, I thought of sanding as a process that necessarily rounded corners and edges, if only a little.

But now I know that by using a fence on my sanding block, I can turn sanding from a de-forming process into a form-reinforcing process.

I like to be able to attach a fence to my sanding block if I'm trying to flatten an area near an edge, or sanding saw blade marks or burns off an edge.  The fence keeps the edge at a right angle to the top of the panel.  One of my flat panel block has a screw-on fence.

My profiled sanding blocks have fences built into the profile.  Doing this is easy: If you're using a router bit to cut the profile, raise the bit high enough to expose the base of the bit, which often has cutting edges, but makes a straight rebate-type cut.  See fig. 1 above for a picture of profiled edges and built-in fences.

A light waxing of the fence can help it slide.  But in general, introducing even a small amount of wax to the workpiece is generally messy and undesirable, and could cause more work and sanding than you'd like.  Instead, I joint my fence, if I can, and sand it smooth, leaving it unfinished.  My next fence will be of large-pored wood, which I assume would slide along the work with less friction.

Velcro & Klingspor for Sand Flee:

I use Velcro to attach abrasive to my sanding blocks.  I get the Velcro from Home Depot, which sells a roll of adhesive-backed Velcro that's about 2" wide.  After jointing the sole of my sanding block (for panels) or cutting the profile (for shaped edges or flutes), I apply the hook side of the Velcro strip to the block.

For abrasive, I use Klingspor rolls for the Sand Flee drum sander.  These rolls are around 2.5" wide, and have a fuzzy back that is made for Velcro.  At $18 per 10 yard roll, it's not cheap.  But its shape makes for efficient use with sanding blocks, and it's cheaper & better than cutting up stick & sand orbital sanding discs to fit.

With the Velcro stuck firmly to the block, and the abrasive paper cut to fit with a razor blade, I never have to worry about the slipping & folding, which can cut through a finish in one swipe.  For profiles, sanding is normally a dangerous business, because an errant brush with sand paper can round over edges, deform coves or rounds, and blunt the decorative curves of an Ogee curve.  With a sanding block cut to match the profile, and with a small fence along the edge of the block, there is no danger of messing up a carefully crafted edge.  In fact, you can easily pack wood putty into a messed-up corner or span of molding, then sand the profile right into the dried putty.  Putting Velcro in the profile (keeping the fence bare wood) allows me to form the flexible Klingspor sand paper to fit the workpiece perfectly.  

Try it

Making a few sanding blocks is a great way to use some scrap hardwood chunks.  Once I had a few different sanding blocks made up during previous projects, I was making better designs, knowing that it would be easy to assemble and square-up complicated workpieces.


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