Hidden Jar Opener

Everybody has a can-opener in their kitchen. But you can't use that when you have a sticky lid on a jar full of jam or some pickles. For that you need a JAR opener that will help you twist off the lid.

To make these, once again my niece Rachel joined me for a project. (This our 5th Instructable together! And we do all the work and writing together, and split our prizes. At least until she's able to qualify for her own student account.) This time we made two jar openers for her grandmas that stay hidden and accessible underneath the upper kitchen cabinets. Because they are fixed to the cabinets, that allows you to use two hands to twist and hold the jar for maximum force. Having this higher force is far more helpful on a sticky lid than having a hand-held tool that you need to grip in one hand while you hold the jar in the other. And you never need to dig through a kitchen drawer to find it.

It is super easy to use and you can open tough lids so fast.

The supply list is very basic.

1. 1/8” plywood, 8x8 inches (in metric, this would be 3mm plywood, 200mm by 200mm)
2. 1/4” plywood, 8x8 inches (in metric, this would be 6mm plywood, 200mm by 200mm)
3. 1 large reciprocating saw blade. If you would like to use our prints, you can buy the exact same model online. It is a Diablo Model # DS0908BFD “9-inch Bi-Metal Reciprocating Saw Blade for Thick Metal”
4. Screws

The tool requirements for this are not that complex either.

1. Jigsaw
2. Drill (This is used both for screwing components together, as well as drilling holes in the reciprocating saw blade. Optionally, you can also use a gas-fired torch and punch when it comes to getting a hole through your saw blade.)
3. Angle Grinder with cutoff wheel and abrasive disc.
4. Safety glasses (This is safer than using the “safety squint”!)

Well you could read all of our words here, or you could have just watched the 33 second video at the beginning of this Instructable. But if you like reading, then read on!

Two pieces of wood are used to support a reciprocating saw blade. This is mounted in such a way that there is a vee-shaped channel.

You press the jar into the vee until it’s tight, then twist the jar in a clockwise manner. The Vee shape keeps it pressed tight up against the teeth on the saw blade, which grabs the lid. You will hear the lid pop and then you know that it’s open!

We've attached a digital copy of our design, but our initial design was actually all drawn by hand.

We started with a blank sheet of paper and Rachel traced a small bottle cap for the bottom of the Vee. Then she drew tangential lines to form the Vee shape, and traced over the blade.

If you would like to skip this step, just print off 2 copies of the sheet that we have attached. You can glue them both following the next step. We have also attached SVG files if you'd like to CNC or Lasercut the wood.

Because this is all going to be hidden away underneath the overhang at the bottom of cupboards, pattern transfer is easy. We just glued the sheet of paper right onto the 1/4"(6mm) plywood and cut following those lines.

Rachel diluted a bit of wood glue with water, then spread it on the wood. The paper pattern was placed over top, and then we stacked some books on top of it so it would dry flat.

If you are using the patterns from the last step, glue one pattern onto each of your plywood sheets (the 1/8"[3mm] and 1/4"[6mm]).

The base is 1/4" (6mm) plywood. That gives a bit of relief above the blade so that a rounded jar lid can easily be gripped by the blade. Rachel used a jigsaw with a wood blade to cut along the lines. Not much else we can say about this step, other than be careful, cut accurately, and wear your safety glasses. Lots of flying splinters!

Refer back the picture in the supplies step to see what your finished base piece should look like if you need to.

The upper unit is 1/8"(3mm) plywood and helps to anchor the blade. Because we only had one set of prints that we had glued and cut through, we needed to make a second drawing for our upper unit. We traced the bottom piece, since the top piece needs to look almost identical. Then we laid the saw blade on top of that, making sure that the teeth were facing out and down into the Vee. Rachel traced around that and we had our upper unit pattern. All she had to do then was once again jigsaw it out.

If you are using our provided patterns, you need to cut out the marked section where the saw blade would be. Once again, refer back the picture in the supplies step to see what your finished base piece should look like if you need to.

This was actually the hardest part of the project. Literally because the steel used for a reciprocating saw blade is very hard.

We started by using an angle grinder to cut off the tang at the bottom of the blade. Then we had to make some holes through that ultrahard blade material.

For the first one, we tried heating it to anneal and then drilling through. We broke 2 drill bits, so that wasn't worth it. I'm sure if I had done it properly with a drill press at low speed and cutting oil, we might have been able to. But I don't have any of that available to me, just a cordless drill.

What we ended up doing for the next blade worked a bit better. We used a propane gas torch to heat the blade up until it was cherry red. Then we laid it on top of a thin piece of wood on an anvil and drove a punch through with a hammer. It was a far more exciting process, with lots of flames and smoke and other high-temperature fun. But you do need to remember that blade is at high temperature and let it cool down before you try to pick it up afterwards.

Better Idea alert: Check out the comment from "42ndOddity" at the end. Instead of punching or drilling, they cut a slot with the grinder in the blade and screwed through that. This would be way easier than how we did it. If you have the grinder and a cutoff disc, I'm going to recommend that method over ours.

Rachel stacked all the pieces together, and fastened them with short truss-head screws (“Wafer screws”).The blade was placed into the little reveal section, and screwed in three places.

Once it was all fastened, Rachel flipped it over and used an angle grinder to clean off all the points.

Rachel and I visited both of her grandmas. We took along a drill and some screws and some safety glasses. We placed the unit underneath the cabinets, with the back edge up against the back wall and the Vee facing out towards the front. Then Rachel screwed the unit into the cabinet bottoms.

All that we had to do then, was show the grandmas how to use it. And that was pretty simple to do. Both of them could easily open jars using it. So hopefully this helps them for many years on those sticky lids!