How to Sand Corners

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Sanding a flat surface is relatively straightforward, but when you introduce corners, things get more complicated. From tight interior corners to the corners of hardwood floors or custom routed corners, this article will teach you how to sand corners. We’ll run through all kinds of sanding tools and give tips for how to sand two of the trickiest corners: rounded corners and end grain.

How to Sand Corners of Hardwood Floors

After sanding the majority of the floor with a drum sander and using an edge sander to even out the perimeter, one stubborn area remains: corners. Learn about the tools you can use to accomplish your corner sanding job.

A man sanding the corner of wood

Use a Detail Sander

Detail sanders are small, easily maneuverable power sanders with a rounded triangle base. They are sometimes called ‘corner sanders’ or ‘mouse sanders’. A detail sander can fit into all but the tightest of spaces, making it perfect for sanding the neglected corners of your hardwood floor.

Use a Palm Sander

A palm sander or sheet sander has a rectangular base that can fit into 90-degree corners without damaging the trim. A palm sander is similar to a belt sander, but instead of a continuous loop of sandpaper, a single sheet is moved back and forth across the wood.

Sand by Hand

If your drum sanding and edge sanding went well, the majority of your hardwood floor should be flat, even, and smooth. Matching that same level of flatness, evenness, and smoothness with a different tool can be challenging.

Sanding by hand allows you to closely monitor the status of the corner as you work. By evaluating your progress as you go, you can avoid over sanding and the resulting mismatch of your corners with the rest of the floor.

Use a sanding block to get into the corner, applying even, medium pressure as you work. Choose the same sandpaper grit progression in the corners as you did for the middle of the room.

How to Sand Tight Interior Corners

Concave spaces, where two surfaces form an acute angle, are known as interior corners. Sanding in these areas is difficult, as access is limited. Maneuverability is key when choosing a sanding tool for tight interior corners.

Use a Rotary Tool

Rotary tools such as a high quality dremel fitted with sanding bands or sanding discs are very small and easy to maneuver.

Use a File Sander

A file sander has a long, thin protrusion that is covered in a sanding belt. It can be used for very precise sanding of small areas, including inside corners.

A man sanding the corner of a piece of wood

Use a Putty Knife

Sandpaper wrapped around a putty knife can enter even the tightest of corners, removing the wood finish or glue, or smoothing the surface.

Make a Wedge

If you measure the angle of your interior corner, you can cut a wedge out of a block of wood that matches it exactly. Cover the wedge with a sheet of sandpaper and sand with short, focused strokes to dislodge old glue. Use longer strokes for smoothing the surface.

Customize a Sanding Tool With Adhesive Sandpaper

Adhesive sandpaper has a sticky backing. This allows you to stick it to whatever you want, turning anything into a sanding implement. When you have a tricky, tight corner that you need to sand and none of the tools on your shelf will do the job, use sticky sandpaper to make your own.

Avoid Tight Spaces by Sanding Before Assembly

When the workpiece you’re sanding is something of your own creation, you have the opportunity to avoid the need to sand in tight spaces. Sand each piece of the project individually before attaching and assembling.

How to Sand Rounded Corners

Use a bow sander to evenly smooth existing rounded corners.

  1. Make or purchase a bow sander. A bow sander looks like a smaller version of the bows used for archery. Instead of a string connecting two ends of a bent arch, they use sandpaper.
  2. Install sandpaper on the bow sander. Most bow sanders are built to accept standard sanding belts. Adjust the clamps at each end until the sanding belt is taut.
  3. Position your workpiece. It’s often easiest to sand furniture legs by turning the workpiece on its side. You may want to clamp smaller workpieces to your work surface to control the pressure during the sanding process.
  4. Bow the corners. Draw the belt back and forth across the surface, allowing the abrasive material to smooth the wood. The lack of a flat backing surface behind the sandpaper allows it to conform to the rounded surface of the wood.

How to Sand End Grain Corners

The end grain of a piece of wood is particularly vulnerable to damage during the sanding process. As the sanding implement leaves the corner of the wood, chips of wood can tear away from your workpiece. It’s a frustrating phenomenon, and difficult to repair. Avoid it by following these instructions.

  • Choose your sanding implement carefully. A sanding sponge or sanding block allows you to exercise the most control over your sanding implement. Handheld power sanders are not precise enough for this task. Avoid using folded sandpaper; it’s difficult to maintain an even pressure with this method.
  • Sand from the outside in.  Place the sanding implement at the corner of the end grain, and move it inward, toward the center of the workpiece. Stop and lift the sander just as you pass the center. Reset the sanding implement and take another pass.

Continue sanding in this way until the surface meets your requirements. Then, move to the other corner and sand the other half of the workpiece.

  • If you must sand across endgrain, use a backer board. A scrap piece of wood can be used to support the end grain and reduce the likelihood of damage. The top of the wood should be flush with the surface you are sanding. Clamp the backer board tightly to the corner of your workpiece.
  • To create a rounded corner, use a sanding block. Start on the non-end grain side and move the block down toward the corner. Maintain contact between the wood and the sanding block as you round the corner. Count the number of strokes you use on each corner, so you can replicate it on the rest of the workpiece.
A man sanding the corner of a wood for flooring

Use a Contoured Sanding Grip on Routed Corners

When the corners you’re trying to sand are part of detailed work such as routed design, a contoured sanding grip can help.

Usually sold in sets, there are contoured sanding grips that match the most common router profiles.

Wrap sandpaper around the grip and pinch it at the top, then slide the grip along the edges of your routed design to smooth it.

An Alternative to Sanding Corners – Liquid Sandpaper

If your purpose in sanding is to prepare the wood to accept an opaque finish, you can skip sanding altogether and opt for liquid sandpaper instead.

Liquid sandpaper, also known as deglosser, removes the gloss on the existing finish, preparing the surface to accept paint or varnish. It does not smooth or even the surface of the wood.

Liquid sandpaper can also be used to prepare intricately carved or detailed areas to accept finish.

Liquid sandpaper must always be used in a well-ventilated area, as it contains chemicals that can irritate your eyes, nose, and airway.

Conclusion

Sanding corners brings up a host of challenges, from preserving sharp edges to achieving rounded profiles. Choosing the right tool for the job is key to success when sanding corners. Sanding implements can include power tools, manual tools, and handmade creations.

Liquid sandpaper can sometimes be used as an alternative to sanding corners.

Ellenkate grew up on job sites run by her family’s construction company. She earned her theater degree from The Hartt School, a prestigious performing arts conservatory in Connecticut. Her design and DIY work from her Chicago loft was featured in the Chicago Reader and on Apartment Therapy.