How to round over inside corners (3 dead simple tricks)

How to round over inside corners? Well, to answer this question, I will take the example of a drawer. Suppose you have made a beautiful piece of furniture in which drawers are present. To make the sharp edges more attractive and less prone to damage, you want to round them over. The outer edges are a piece of cake, but how do you round over inner corners?

There are three very simple options to round over inner corners:
Either, you try to plan your work in such a way that you round the corners before mounting. When the assembly has already been done, you can round over inner corners with a chisel. A final option is to round the inside corners with a file.

When rounding over corners with your router and round-over bit, the inside corners are left unprocessed, which appears sloppy. Read on if you want a beautiful finish but don’t know how to round over inside corners. You’ll learn which approach is optimal for rounding inner corners in this post.

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How to round over inside corners

Round over inside corners before assembling

A first option to answer the question of how to round over inside corners is to first plan the process of your project, then make your round overs and finally mount all pieces together.

By making good planning, you can estimate which parts and their edges should be chamfered or rounded. Please note, you will have to plan this very well because mistakes are made very quickly here. To help yourself with this, make a drawing in advance that gives you a good view of all parts. You can number them to make it even clearer.

Rounding the corners before mounting is a great idea, but there is one downside to it. When rounding in advance, the bevel or rounded edge will run the full length of the board. This means that after mounting, the chamfer is clearly noticeable where you will connect two boards. If this doesn’t bother you, and you like a good preparation, then I am convinced that this tip about how to round over inside corners is a good choice for you.

Round over inside corners with a chisel

If the hard work of planning isn’t your thing, or you’re afraid of making mistakes, there’s this solution on how to round over inside corners. You will first do the assembly of the parts for which you want to finish the inner corners. Only after installation will you then finish the edges, as well as the inner corners.

When working with a round-over bit on the router, you will run the bearing wheel against the wood, and you can almost blindly create a rounding or chamfer that is uniform along the entire length of the wood.
However, it is recommended to always work with perfect router bits so that you can avoid burn marks at all times. You can read all the info you need for this in my blog, “why is my router bit burning the wood”. Before you start working with a router bit, you should definitely read this article, it is full of useful tips.

When you reach a corner, the tracking wheel ensures that you can’t go any farther, resulting in a half-completed bend rounding. This irritates me greatly. All that’s left is to gently finish the corner with a sharp chisel. Place the chisel in the same direction as the last rounding and try to complete the rounding in small steps while keeping the same shape. Change your direction and board frequently, such that the point where you meet in the corner looks beautiful. To know what chisel to use, please check out my article, “3 Most Important Wood Chisels You Should Have”.

Round over inside corners with a file

The previous trick with the chisel works great, I use it myself quite often. But from experience, I learned that this trick works very well on edges that need to be chamfered, and less well on edges that are rounded.

The chisel is, therefore, less useful to make rounded corners. I’m not saying a chisel is useless here, but it does take a lot of work and effort to maintain the proper form of the rounded corner. The file is a much more suitable tool.

You can make it very easily with a file. What you need to do is position the file perpendicular to the edge you want to round. By moving the file forward and pushing the nose down at the same time, you can perfectly mimic the curve you already made with the router bit. Do this in light passes and be careful not to take away too much material. Here too, regularly alternate between the different directions of the boards, so that the corners you work on point towards each other. To refine the rough texture left by the file, you can sand again with 220 grit sandpaper.

How to round over inside corners – Conclusion

At first glance, rounding inside corners can be a difficult job, but you definitely want them to be neatly rounded, just like the rest of the edges. Well, if you use the tips from this article, you will now know perfectly how to round over inside corners.

You can round edges before mounting your workpieces, or you can use a chisel or file to create the perfect rounding all the way to the corner where the two boards are joined.

I recommend trying each of these three tips to round inside corners and see which tip works best for you. With a little practice, you can now neatly finish any inside corner the way you want. I have to say that all three of these tips work great for me and depending on the project I’m working on I will choose a method where I get the best. If you’ve watched my YouTube videos before, I’m sure you’ll see me using each of these methods.