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Sanding Block Question

4K views 34 replies 22 participants last post by  gfadvm 
#1 · (Edited by Moderator)
I have built a bunch of sanding blocks (one for each grit) from some I've seen done by fellow LJs. Now the question is: should they have some sort of 'padded' base or should it be just bare wood? I've used that thin white floor underlayment as cushion for some in the past but don't know what others recommend.
 
#5 ·
It depends on what you're sanding. Ideally, the shape of the sanding pad matches the shape of your work. If you're sanding a flat surface, a hard, flat sanding block is good. It also allows you to use it sort of like a block plane and make faceted edges vs. a softer block which will round off corners. A hard backing also allows you to put more pressure and really hog off material with a coarse grade of sandpaper.

I use firm rubber pads for a lot of tasks, and my shopmade wood blocks for others. I don't bother with any backing on the wood blocks.
 
#6 ·
If you think about it, any large surface you sand with a unpadded block will not conform completely to the surface being sanded. At least a couple layers of cardboard under the paper. You can get away with it on small pieces. I prefer ROS for large surfaces.
 
#7 ·
I picked up a piece of granite once I was going to use for a sanding block once, but alas it dissappeared before I got it back home, it was in a trash bin too…

The key is you want your block to be harder than the wood you're sanding so that it won't wear, for profiles I typically use my hands, as I can make my hand conform to pretty much any profile so…
 
#10 ·
before sandpaper the smoothing plane was used. i use 1 inch mdf or any scrap hardwood that is flat and contact cement the paper on, when the paper gets worn out i throw it away. when block sanding a flat surface you do not want any rubber or cork or anything soft as a backing. when contour sanding make a pattern block that fits your profile.
 
#11 ·
Thanks for all the replies. I had the feeling that my underlayment backing was causing my paper to snag and tear. I'll try it without but I need to fill the hole in the center of the bottom or cover it with a thin strip of hardwood.
 
#12 ·
Since I make lot of boxes, I dont use a sanding block per-se. I glue a full sheet to a 15×20" piece of MDF and move the box across the full sheet. I have a full set 80, 100, 150, 180 and 220. It really helps to keep the flat parts flat.
 
#13 ·
I have two sanding blocks that are dimensioned such that I can hand hold a quarter sheet of paper. I faced one with truck inner tube and the other with 1/8" sheet cork.
 
#15 ·
I would tend to use just the bare block Andy. Of course it could depend on what you are sanding I would have thought. Straight and flat, bare block, any coutours then some form of "padding" may be more appropriate.

Too much of a cushion may not sand the area flat and simply follow the contours of the piece, much like a smoother plane on a long wavy board.
 
#17 ·
It's a specious argument that Too much of a cushion may not sand the area flat and simply follow the contours of the piece, much like a smoother plane on a long wavy board.

If the surface ain't already flat, rubbing with 100 or 180 sandpaper won't get it flat. Plus without a bit of cushion, the paper will tend to load and glaze, especially around the edges, leading to premature failure.
 
#18 ·
Hmmm… Clint and Russel raise a good point. Unless your work surface and your hard sanding block are both exactly the same shape, then you're only sanding with the spots that actually make contact. I guess it depends on the goal. If you're shaping the surface, you want a more rigid pad that's the shape you want - flat, wrapped around a dowel, glued to a curved block, whatever. And it seems like it would really pay to take the time to get the shape right, eg. flattening a wood block like a handplane sole.

If you're smoothing a surface for finish prep, then a softer backing will use more of the abrasive surface and allow the sandpaper to conform to whatever shape the surface is, thus sanding the entire surface. With a hard block, any low spots in an almost flat surface won't get sanded.
 
#20 ·
I made up several as Christmas gifts for friends this past year and have several in my shop of various sizes and shapes. For a padding I bought the non-slip drawer liner material from a big box store. I attached it using 3M 77 spray adhesive. The padding can be replaced when worn out by peeling and scraping it off. The padding allows a little forgiveness when sanding and I think the paper last longer and does not tear as easy. I made up 1/2 and 1/4 sheet ones, and have a couple of speciality ones (round and cove types). I use to use ones without the padding and would tear the sanding paper. Most of the people I gave them too really like the padding, have had several compliments about them.
 
#21 ·
A friend of mine makes blocks that hold a sanding belt. Don't know the exact size belt off hand, maybe 4 inches wide by 24 as the blocks are over a foot long (made from MDF). They are best at edge sanding rough cut wood or when trying to back plane a cabinet frame during installation.
 
#22 ·
I use small sanding blocks with self adhesive sandpaper on two adjacent sides. I use it like a shoulder plane to fit tenons. I also use it to ease sharp edges and corners.

As far as tabletops and flat panels, I just use my 5" ROS and work through the grits. I find it leaves a nicer, more uniform finish than a sanding block can.

Good luck
 
#23 ·
I use both. If I want to maintain a flat surface I use a straight wood block but for contours and round overs I like to put a piece of 6mm craft foam between the block and sandpaper. Another super sanding block material is cork. It has just enough "give" and really helps the paper to cut.
 
#26 ·
Wow! Lots of opinions. To clarify: all the surfaces I'm concerned with should be flat (planed and drum sanded to 120 grit). Interesting that several of you suggest padding to prevent tearing the sandpaper. I've never tried unpadded blocks so looks like I'm gonna have to try them and decide which works best for me. Thanks for all the interest and comments.
 
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