How to Choose the Right Sanding Block
The sanding block gets its name because once upon a time it was just a block of wood with sandpaper stuck to it. The hard, flat block allowed you to sand to a much more uniform surface. Later, the heavy rubber style “alligator” or “vampire” sanding blocks were invented with teeth in them to grip a 1/4 strip of sand paper, but that compared to today that is still stone age technology. Now there are blocks of all shapes, sizes and materials, for use on different shaped panels, and make all of our lives easier.
Sandpaper has come a long way too, but nothing much has changed about how you use it. It’s just formulated with different abrasives, glues and backing to cut faster, longer and not fall apart. There are also neat innovations like adhesive backs and hook and loop attachment. But even with the advances since the 1980s, it’s pretty much the same process Daniel used in Karate Kid, back and forth, back and forth, until you build up the muscle memory to defend yourself, or block sand a car. Remember, when sanding with a block use alternating, crisscross strokes, and always push the broader edge of the sanding block as the leading edge, not the narrow one.
If you need more information of block sanding and body work, the Eastwood YouTube channel and Tech Library are full of helpful how to stuff. Kevin Tetz has done quite a few videos demonstrating exactly how to do body work and prep for paint. According to his expert opinion, any paper with a grit coarser than 220 is for shaping, and finer than 220 is for sanding.
Shaping is what you do to grind down welds, smooth body filler, and remove tiny waves from the metal work. Often times you are staring with something like 36 or 40 grit to grind down patch panel seams or body filler. Gradually you get finer and use something like 200 grit to shape high build primer before applying a sealer, and starting to paint.
Sanding is what you do to promote adhesion of the next coat of paint to an old coat that is beyond the time window where it will chemically bond. Sanding is also what you do to get rid of paint imperfections like orange peel and drips. You can and will use sanding blocks at both of these stages, but they are different types.
Rigid – Typically when doing initial shaping you will be using a very coarse paper, and a hard block, or even some sort of power tool, depending on what you are shaping. No one needs an explanation of how to grind a welded seam of a patch panel down with an angle grinder. Once you are beyond that stage though, you likely will be using a rigid block.
This block is really the least advanced and can still be a hunk of 2 x 4 cut the size of your hand with adhesive backed paper stuck to it. For more advanced options try the 2 handed Eastwood Contour Rigid Sanding Board (#31056 or #31057), Dura-Blocks (#31160 7 piece kit, or sold separately), or the Adjustable Flexible Sanders (#20326) with all their stiffening rods in place. You can even make your own blocks to fit in unusually contours, or tight spaces out of a piece of dowel, a paint stirrer stick, or anything handy.
Shaped – If you are doing a repair on a surface that crosses over a body style line, or is a concave panel, you’ll want to find a shape that matches it as closely as possible. This helps you get an accurately shaped repair without a lot of artistry and free hand sculpting. This is where making your own sanding block is useful.
Eastwood has lots of different types of these, including soft blocks that can be shaped to your will for sanding large contoured areas. Again Dura-Block makes a great kit (#20553) including round, and teardrop profile nearly rigid blocks, the Style Line Soft Sanders kits (#12555 or #19311) include different rigidity, and a wide range of profiles for most any part that needs sanding.
Semi-Rigid – Semi-rigid blocks are prefect for fine shaping, contouring, and curved, crowned surfaces. Let’s face it we talk a lot about body panels being straight and flat, but even on a boxy Volvo, there are subtle curves stamped into every body panel. In order to properly smooth and shape these you need semi-rigid blocks after the initial shaping has been done.
A great tool for this is the Adjustable Flexible Sanders (#20326) with the removable rods, because you can start with them full hard for flatter areas, then make them less rigid as needed. To make short work of large areas try the 2 handed Eastwood Contour Flexible Board Sander (#31007). Then there are the palm sized Semi-Rigid Sanding Blocks (#34046) for smaller detail areas.
Flexible – The final shaping you do, and most of the block sanding of paint imperfections, is going to be done with more flexible blocks. It just makes sense. The softer and more flexible a block is the less aggressive it is going to cut into the surface of what you are sanding.
The Adjustable Flexible Sanders (#20326) with no rods in them are good for this, if you are doing a large area at once. Otherwise the Flexible Sanding Blocks (#34055) are great, or even the softer side of the Semi-Rigid Sanding Blocks (#34046) is it’s a relatively flat panel you are shaping.
Block Sanding Paint
Funny that many people when they think about block sanding are thinking about this step. Block sanding paint happens after the paint and primer are all done and you are just fixing the final imperfections and getting the mirror smooth gloss. This type of block sanding doesn’t really need all the various blocks at all. A simple semi-rigid, or flexible pad is really all you need. For larger flat areas even the old fashioned rubber palm block will work. Or use the more modern version of that old stand by the 6” Flexibility Palm Sander (#31171)
Hopefully this little run down of sanding blocks and their proper use has helped you out. Of course if you have any questions you can find answers in our tech library, our online restoration forums, or our help line. The Eastwood YouTube channel is also full of helpful videos showing how to use the products we sell, and how to do just about anything when it comes to body work.