Can Openers for Dummies

I'm officially old now:the other day I had to teach a 20-something worker how to use a can opener. This poor soul has been raised his entire life with pull tabs on canned goods or an electric can opener on the counter, and had no clue how to open a can of soup with the opener on my Boy Scout knife (which is older than he is). A manual can opener is not some miracle of modern science; they've been around since Napoleon Bonaparte funded the invention of canned foods.

Looking at the three can openers available in my EDC gear (redundancy is part of my life), I thought that I should maybe explain these curious anachronisms to the younger readers of this blog just to get the information out there. While there is no such thing as a stupid question, many people won't ask for information that they feel they should know or don't know that they don't know. The more experienced readers can either skip this article or read through it and add their two cents' worth in the comments.

Canned food is one of the overlooked miracles of “modern” life. With proper preparation and a good seal, canned food allows us to store food for a year or two and enjoy the nutrients and tastes long after the food is harvested. Most canned food is placed into a tin-lined steel can and a lid is roll-crimped onto the open end, sealing out air and contaminants. The roll-crimp leaves a defined “lip” around one or both ends of the can, depending on the construction of the can, and that “lip” is the key to using an opener to get to the goodies inside. Electric openers, and the manual ones that look like a pair of pliers, use a metal gear on the bottom of the lip for gripping and moving the can while a round cutting wheel pierces the top of the lid and shears through the metal of the lid as the can is rotated. There are variations that flip the cutting mechanism 90° and cut through the can just under the lid, but the method is the same.

Simple manual can openers come in various shapes and sizes, and they fall into two styles:

Convex Cutter

The cutting edge that pierces the lid faces away from the rest of the opener, and is usually beveled in two stages or angles. The one on the “bigfoot” pocket tool's upper arm has the break between the two stages about centered, while the one on the clip knife is roughly a third of the way along the cutting edge. Leaving the “sharp” edge exposed lets you use it for other purposes more easily, like scraping or scratching a surface.

I don't have a good close-up camera, so I can't show you the profiles of the cutting edges, but the “bigfoot” has a flat side and a beveled side similar to a chisel,while the one on the knife has a double-beveled edge like a common knife blade. The chisel style seems to be more efficient in my experience, and it leaves a cleaner cut in the metal. Convex cutters make small holes and take more time to open a can.

To use a convex opener:

1. Hook the lip of the can with the open portion of the cutting head.
2. Lift up on the rear part of the opener to pierce the lid.
3. Release the pressure on the lid without removing the opener.
4. Rotate the can a fraction of an inch towards you.
5. Repeat steps 2-4 until the can is open.

Concave Cutter

This is the style that I prefer. The cutting edge is on the inside of the opener, which makes it less likely to damage or be damaged by other things. Most of the concave style openers have a rounded cutting edge rather than a stepped or staged edge. You can see the obvious curve to the cutting edge on the BSA knife.

The venerable P-38, or John Wayne can opener, is a convex style as the cutting edge is rounded and it pierces and cuts towards the operator. The curved cutting edge gives a smoother and longer cut in the lid with less effort.

To use a concave opener:

1. Hook the lip of the can with the open portion of the cutting head.
2. Lift up on the rear part of the opener to pierce the lid.
3. Release the pressure on the lid without removing the opener.
4. Rotate the can a fraction of an inch away from you.
5. Repeat steps 2-4 until the can is open.

Using a Knife

Yes, I have opened cans with a fixed-blade knife before. It's inefficient and damages the point on the knife, but it works if you forgot to pack (or lost) a can opener that weighs a few grams. I've seen a lock-blade knife fail while trying to puncture a #10 can, leading to a lot of blood all over the food we wanted to eat, so I don't recommend using folding knives.


If you're setting up a Bug Out Location with lots of food stored in #10 cans, I'd suggest you look into getting a commercial-grademanual opener that mounts to a bench; it's much faster and easier than the pliers-type or smaller openers, and once you get used to one they are faster than most electric openers. For a Bug Out Bag, be sure to include a P-38 or the larger P-51 opener.