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How to Choose the Correct Sandpaper Grit

Anyone who has had the pleasure of having to prepare wood for a recoat of paint or varnish will know it can be hard work. But you will also know how important the preparation is.

 

It is probably the most important step in refurbing your wood because if you don’t get the preparation correct it won’t matter how well you paint it or varnish it the result will always be a poor looking recoat.

 

Choosing the correct sandpaper is a really important step to getting your wood prepared for a recoat. Manual sanding is not much fun but there are many times when you can start with an electric sander until you remove many of the outer layers.

3M Aluminum Oxide Sandpaper, Assorted Grits, 9-in x 11-in Sheets (9005NA)

Choosing Sandpaper for Electric Sanders

 

A high-speed belt sander is used to sand large surfaces, such as wooden floors, doors, and anything with a big surface area.

 

Portable belt sanders are very useful for doing jobs that require the removal of tough stubborn outer layers.

 

Finishing sanders, also called orbital sanders, are second to none to remove thinner layers.

 

For small, intricate jobs or for surfaces with many contours sanding work is done by hand, with sandpaper bent to the correct shape or placed on foam or wooden block.

 

One of the common mistakes people make is the wrong sandpaper choice. The lower the grit rating for the sandpaper the bigger the sanding grains will be. For really tough surfaces the high grit sander paper is the better choice and if you have fine light sanding work to carry out then the higher grit rating is a suitable choice.

 

Using too low-grade sandpaper that is too coarse can create problems with sanding away at the wood as soon as the paint layers on the wood that you want to remove are gone.

 

This happens very quickly so you think you are just taking the paint then you check and it has gone too deep and has started to sand the wood down.

 

This can be a real problem if you are sanding curved or shaped wooden pieces because it will misshape the wood and cause damage to any patterning on the wood you wanted to preserve.

 

You should take it easy when you are close to the wood and change sandpaper grade to a finer one.

 

Sanding work is usually done in steps; First thick sandpaper is used until you remove the majority of the outer layers and it is then normally finished with fine grain sandpaper.

DEWALT Random Orbit Sander, 5-Inch (DWE6421K)

Understanding Sandpaper Grit Numbers

Hand sanding block

This block is useful for sanding small flat surfaces. To sand curved surfaces, sandpaper is shaped with a foam pad. The sandpaper fits the shape of the workpiece grooves and contours.

 

Thick sandpaper No. 60

This sandpaper is used to sand hardwood floors and to prepare tough surfaces. The sander moves counter-grain to remove the material faster.

 

Medium sandpaper No. 100

This sandpaper is used for better results in the initial polishing of the wood. The sander should move in the direction of the wood grain so that the surface is as smooth as possible.

 

Fine sandpaper No. 150

With this sandpaper the final finish is given to the surface of the wood. Fine sandpaper is used to prepare the surface of the wood for varnishing; it is also used to smooth the joining edges of pressed fiberboards.

 

Extra-thin sandpaper No. 220

Extra-thin sandpaper is used to polish the prepared surface of the wood before varnishing, or between layer and layer of varnish.

 

Finishing sander

A sander for good quality finishes has a high-speed motor and orbital movement; with this sander can be sanded flush in very small areas in terms of workspace. For rough sanding, the sander moves against the grain. Finish sanding is done by moving the sander in the direction of the vein.

 

Sanding accessories. These accessories are mounted on an electric drill. The following accessories are displayed from top to bottom and clockwise: abrasive disc for quick work, reels and strip disc for sanding contours, and a reel mounted on an adapter.

 

Sanding Safety

You should always wear a dust mask when you are sanding wood or paint because the fine dust particles can get into your lungs and cause serious damage.
When you are using an electric sander you should also consider wearing goggles to keep the dust out of your eyes. Fine dust can scratch your eyeball and cause problems.
Many electric sanders come with a dust extraction feature so it is worth setting that up if you can.