Commercial Sanding Blocks
One reason I do not like commercial sanding blocks is that they almost
always use too much sandpaper. Sandpaper is wrapped around the
block and clamped in place using a method that never gets the sandpaper taut or
flat on the block.
Because the paper is loose on the block, grit and dust can get between the block and the paper.
This dust prevents the paper from laying flat on the block, will cause the paper
to wear out faster and makes the block more likely to gouge the wood you are sanding. Sandpaper is not supposed to make
the surface worse!
This is why I always glue sandpaper to blocks using spray glue. I only use as
much sandpaper as is necessary to cover the face of the block so very little
gets wasted. When the sandpaper needs to be replaced, a heat gun softens the glue so the
paper can be removed. Lacquer thinner cleans off the glue left behind on
the block.
Another problem with commercial sanding blocks is that they are
always the wrong weight. To properly sand something, the sanding block
should be heavy enough to feel solid, but light enough to give you feedback of
what's going on while you are using it.
It is hard to describe, but when
you are using the right sanding block you know it by feel. Always use the
largest sanding block you can. Obviously some things will limit the size
of the block (such as room for you to hold the part), but a larger block will
make it easier to sand things flat.
The only time I will sand without a sanding block is
when I have gotten down to final smoothing of a component that has compound curves
and I want to knock off the facets left from using a sanding block. I use
very fine paper (600-800) that will not drastically change the shape. 400
paper is not very fine when sanding soft balsa and can change the
shape of it noticeably in a short time.
One little trick I like is
for sanding small, flat parts. Instead of trying to hold the part in my
hand, I put it on a sanding block and then use another block to sand it.
If you do it right, you can get the sanding block the work is resting on to grip
the part so it does not move when you sand it with the second block.
You can also put a flat
sheet of sandpaper on the workbench and move the part over it. However,
you should rotate the part because it is difficult to put even pressure on the
part and you may sand it to an unintentional taper.
My other most-used sanding block is a T-bar that is 22" long.
That one gets a workout when it is time to sand wing panels. I also use
spray glue to adhere the sandpaper. Sticky back sandpaper is not very good
quality to begin with and it also tends to peel up. It also costs much
more than regular sheets of paper for a given quantity.
No matter what type of paper you use, you should clean the sander with
solvent before putting new paper on. I normally use lacquer thinner or
acetone.
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There are times when you want a sanding block that is firm but flexible. So far I haven't found
any material that seemed just right. I was asked to try
Dura-Blocks which are machined firm EVA
rubber (which is Ethylene Vinyl Acetate resin and not rubber at all) sanding blocks in several sizes and styles.
I received a 7-piece Dura-Block kit to evaluate. The set includes six sanding blocks and a bar of
pumice-type soap that wasn't include in the set provided for review.
The set came in a colorful airbrush art box featuring two creepy clowns. This box isn't doing good things
for my psyche because I thought clowns were creepy even before
Poltergeist made it normal
to think clowns are creepy. I think I'll hide the box under my bed so I never sleep again.
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Three of the six blocks are machined to the shape shown below. One of the blocks is a rod
approximately 1-1/4" in diameter.
The remaining two blocks are rectangular cross section. |
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I haven't had the opportunity to do a proper review yet so this is just an overview and my initial impression.
The machine-shaped blocks are fairly thick and comfortable to hold. While they aren't as rigid as a
hardwood sanding block they are fairly firm.
I wouldn't use them for flat sanding balsa wood structures but
I think they will be right at home sanding items having long or compound curves such as turtle-backs and balsa
cowls.
I think these blocks will really shine when blocking primer and paint. None of the sanding blocks I
normally use are water-proof but these are which means I can use them to wet-sand which is the best way to sand a
finish.
I'm not real clear on how sandpaper is supposed to be attached to these blocks but my plan is to spray a light
coat of spray glue on the sandpaper only. I won't apply glue to the block because I suspect the solvent used to remove
the glue will eat the foam. When the glue on the sandpaper is just drier than tacky I'll attach it and see how
well it holds. I'll make adjustments to this method as needed. |
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