Make Perfect Rounded Corners With Minimal Tools

This short instructable will show you how to make perfect rounded corners with only minimal tools.

This method is really a variation on the 'bisecting an angle' technique you may have learned way back in your geometry classes.

Step 1: Tools and Materials

You will need a compass and a cutting tool appropriate for your material.

I'm using a piece of scrap mdf to demonstrate the technique, but it should work with any material.

Step 2: Set the Compass

Set the compass to the desired spacing. The distance between the ends of the compass will be the radius of the corner. If you don't have any particular radius in mind, just make it look good.

Step 3: Point to Point

Place the sharp point on your compass on the corner you want to round off. The closer you can get to the point of the corner the better.

Step 4: First Mark

Rotate the compass to make your first mark at the edge of the workpiece.

Step 5: Second Mark

Repeat the previous step to make your second mark at the other edge of the workpiece.

Step 6: Reposition the Compass

Now, lift the pointy end of your compass and place the it on the point where the edge and your mark intersect.

Step 7: X Marks the Spot

Rotate the compass to make a mark near the center of the workpiece. Move the compass and repeat for your second mark.

You should now have an X on your workpiece.

For you geometry nerds out there, we've just bisected the angle. If we draw a line between the center of the X and our corner we've just exactly split the corner in half.

Step 8: Round the Corner

Finally, move the compass one last time. Place the pointy end on the center of the X you made.

Rotate the compass to draw an arc between your original two marks.

You now have a perfect template to round your corner off.

Step 9: Cut Along the Line

Now just cut along your line, and taa daa! A rounded corner.

Need more than one? Just repeat the process as many times as you need.

Comments

[Icedvovo]

Jar lids and dinner plates always work for me. ;)

[JGDean]

It's a good method that I've used often when I need a particular radius. I even have an old beam compass for radii up to 14", but they're hard to find. (I was a draftsman for 15 years, a long time ago.) If you need really large arcs or circles, there's the "stick with a nail and pencil" trick - get a stick that's longer than the radius you need, drill a hole through it that will just fit your pencil, then measure your radius from the point and drive in a sharp nail. With your improvised beam compass, use your method to mark your arc (or circle). You can even extend this to very large circles (for landscaping, etc.) by driving a stake or large nail at the center of where you want and using a rope or wire with a loop in it, and scribe your arc with a stick or even spray-paint.

But it's easier and requires even fewer tools to find something of the radius you want (like a coin, a spool, can, bowl, bucket, etc), place it so it's just touching the two sides you want and trace around the edge.

[BeachsideHank]

I use old school drafting templates, both circle and French Curve, they come cheap nowadays since most drafting is done by software, thrift stores and Craigslist usually have these, given up by draftsmen (or their widows). ☺

https://www.google.com/search?q=drafting+templates...

Your method is great for a custom in between radius though.

[pfred2]

Buying used drafting supplies is a topic I am well versed in. Circle templates are not generally available used. Because if they were I'd have a lot more of those myself. As it is I am considering buy another new one. I have two sets of drafting instruments, but I'm presently sharing one small circle template between them. Which is making having the two sets decidedly less convenient for me than it should be. I suppose it depends on where you are what is available. I mean if you're in an area that was known for engineering a couple decades ago then things might be better. Then again circle templates are known to fail often too.

[43totheN]

Good to know. I've never seen drafting templates that I can think of. I'll be on the lookout for them now.

This method was one of those 'I need rounded corners for a project and all I have is a compass' ideas.

[joen]

I have always used a bottle cap of the right diameter. Just touch the edges of the corner with the edge of the bottle cap and draw the curve.

[43totheN]

I've done that too. I've never been happy with the results though. It seems like I never have the right size for the project I'm doing.

[pfred2]

You could get a drafting template. They have lots of sizes.

[mrmetallica]

that is so good and very helpful thank you.