Choose the Right Block

True Blox are a different kind of block.  Almost all other sanding blocks in the past were basically the same, there were only a couple of them, and they were just different lengths.  They were very general purpose. 

There are a lot of different True Blox, 9 different thicknesses, and 7 different lengths. What’s the point, and how do you choose which block to use? 

  • First, all the blocks with the black handles are for body work and blocking primer. 
  • Choosing a block is based mostly on how much it flexes, which is determined by the block’s thickness. 
  • The longer a block is, the more flexible it will be. So a 12” long 3/8” thick block will be pretty rigid, while the same block 22” long will be a little flexible. 
  • The correct block should take a small amount of tension to form to the shape of the panel. 
  • The block should do most of the work sanding the correct shape, so choosing one too rigid or too flexible won’t work as well. 
  • If the center of the block is doing most of the sanding, it’s too rigid.  
  • If the block seems too loose and the ends are sanding too much, it’s too flexible. 
  • Most times, several blocks are needed for one panel. It’s encouraged to switch blocks freely until one feels right. 
  • Usually, the longer the block the better. It should not feel awkward though. It typically shouldn’t be longer than the panel is (the edges will get sanded too much)
  • A bigger block does not mean straighter body work.  So don’t jump to grabbing the thickest and longest block thinking it will work better. 
  • The small blocks without handles are for wet sanding. The sandpaper is wrapped around them, and you hold onto the flaps of the sandpaper. 

1 comment

  • What blocks would work best on a Corvette? I’m working on one as we speak. Thanks

    Jon parker

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