Introduction: Heavy-Duty Nutcracker
A friend goes to Hawaii every year and brings back a sack or two of macadamia nuts in the shell. When he tries to crack the nuts with a hammer, the force required is so great that he crushes the meat of the nut, too, when the shell finally yields. He needed a special nutcracker. Here you see it in use.
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Step 1: Make Teeth in the Jaws
I have some 5/8 x 5/8 inch bar stock someone gave me. It is more than strong enough to make a base for the nutcracker and also the jaws.
When machining needs to be done on a smaller piece that would be difficult to hold I like to do the machining first and then cut the piece away from the larger bar stock. Use a thin cutting wheel to make teeth on the jaws. It does not matter that the jaws resemble a square wave rather than saw teeth. One of the jaws will be 1 3/4 inches long. When the teeth have been cut for it, cut it away from the bar stock.
Cut identical teeth for a second jaw and make them over a length of 1 3/4 inches, also. These teeth are enough to grasp the shell of a nut and hold it while it is being cracked.
Step 2: Cutting the Second Jaw
The first jaw is at the right in the photo. Teeth have been cut into what will become the second jaw. Masking tape marks where it will be cut off from the rest of the bar stock. The line for the cut is 2 inches from the end of the jaw. The cut is at an angle of 50 degrees. A 50 degree cut bisects the 100 degree angle of the second jaw off of the base for the nutcracker.
Step 3: Prepare to Weld
After cutting the second jaw away from the bar stock, turn the second jaw over and grind a chamfer on the two ends. Then turn them to meet as you see in the photo. The angle of the jaw to the base of the nutcracker should be 100 degrees. The "V" chamfers will be filled with weld material for a very strong weld. Leave a small gap of a very few thousandths of an inch between the two pieces so the first weld penetrates fully.
The first pass is called a root weld. After welding a bead on one side, turn the assembly over and make a bead on the other side. Alternating sides for welding like this minimizes distortion by heating both sides evenly. Clean away slag before laying down a new weld bead. Be careful to avoid any slag inclusions. Trapped slag will make a weaker weld.
Step 4: Weld Completed (for Now)
The second jaw has been fully welded to the base of the nutcracker. Irregularities where the weld beads rise above the flat surface of the bar stock will need to be ground down smooth whenever it is convenient to do so.
The first jaw made is shown in the approximate position it will have when the nutcracker is finished. An axle on which it can rotate will need to be added, but first there is something else that needs to be done.
Step 5: Fitting Welded to Backside of the First Jaw
A fitting will be needed on the backside of the first jaw (the one that moves on an axle). This fitting will be part of the linkage that makes the jaw move.
Weld a bar of 3/16 x 3/4 inch stock to the back of the first jaw, but make it offset from the side face that is against the aluminum I am using as a welding table. The offset is 3/8 inch. I used a piece of wood this thickness. I also cut the end of the bar stock at a slight angle so the fitting angles upward just a little. I used 20 degrees as my angle.
Step 6: Cut the Bar Stock and Drill a Hole
When finished welding for this step, I cut the bar stock to 1 1/8 inches on the top side with a 90 degree cut. Then I drilled a 5/16 inch hole about 7/8 inch from the back face of the first jaw. The photo is actually for a later step, but illustrates the fitting welded to the back of the first jaw with the 5/16 inch hole.
Step 7: Weld an Axle for the First Jaw
Cut a piece of 5/16 inch rod 1 inch long. Use a square to position it across the base of the nutcracker. Center it so the amount of overhang by the rod is equal on both sides. Weld on both sides of the axle for good penetration in the nutcracker base.
Step 8: Cut Two Pieces and Drill
Cut two pieces 2 inches long from the 3/16 x 3/4 inch bar stock. Clamp them together and drill a 5/16 inch hole through both near one end. Grind away all burrs.
Step 9: Clean Up the Axle
Weld bead may have run over the side of the nutcracker base. This will interfere with the fit and function of the nutcracker. File or grind away any weld material that keeps the sides from being flush and smooth. Dress the axle ends with a file to remove any weld material that does not belong, also any spatter beads that keep the axle from being smooth. This photo is from smoothing a second axle in a later step. Blue marks to the side of your weld means the metal became sufficiently hot to make good penetration and a good weld.
Step 10: Dry Fit the Pieces From Step 8
Dry fitting the two pieces drilled in step 8 insures they will work properly. Their inner face should ride smoothly against the face of the 5/8 x 5/8 inch bar stock for the base. Use a file to correct any problems.
Step 11: Weld the First Jaw to Its Mounts
With the two jaw mounts from step 8 fitted over the axle ends, insert the first (movable) jaw between them. Position the jaw as desired and clamp in place for a couple of tack welds. Be certain the jaw and its mounts have a good range of unrestricted movement before tack welding. Then remove the clamp and weld wherever there is space for a bead. I welded some on the backside of the first jaw from the right side of the photo, as well as on top of the jaw mount pieces.
This nutcracker is primarily for macadamia nuts. The smallest macadamia nuts are about 5/8 inch in diameter. The bottom area of the jaws is spaced for 5/8 inch in the photo.
Step 12: Add a Second Axle
A second axle is needed to complete the mechanism, but it extends over only one side of the nutcracker's base. Note its position from the photo. Position it in place 6 inches distant (on center) from the first axle. The rod for this axle is 1 1/4 inches long. Remove any burrs after cutting it to length so it will pass easily through a 5/16 inch hole drilled in steel. Dress it with a file for smoothness as shown in step 9.
Step 13: Make an Actuating Lever
The lever that moves the nutcracker mechanism is from 3/16 x 3/4 bar stock. Make it 4 3/4 inches long. Angle the top end at about 20 degrees as shown. Drill two holes 5/16 inch in diameter near one the end cut at 90 degrees. Make the holes about 7/8 inch distant from one another on center.
Notice that the distance between the axle hole(s) in the lever is less than that in the movable jaw. This means considerably more movement is required in the lever for considerably less movement in the jaw. This acts as a force multiplier.
Step 14: Make Four Squares With Holes
As you can see, I drilled the end of the 3/16 x 3/4 bar stock with a 5/16 inch hole. Then I cut it off to make a square with a hole. Four of these are needed. They need not be extremely precise. Three will be used as retainers, like a permanent nut. One will be used as a spacer
Step 15: Thicken the Lever for a Better Bearing Surface
I decided to add double thickness in the lever to give the axle hole a wider bearing surface. This will make the lever more solid on its axle. Grind away any weld material that keeps the surface from being flush and smooth.
Step 16: Weld a Permanent Nut Onto the Axle End
Place one of the hole squares over the end of the axle. Press it against the base of the nutcracker. Weld the end of the axle to the hole square for a permanent nut or retainer. The photo is actually from a later step, but illustrates this step well.
Step 17: Connect the Lever to the Movable Jaw
How long should connecting bar between the lever's 2nd hole and the fitting on the back of the movable jaw be? I placed a macadamia nut in the jaws at about mid-range and secured the jaws with a spring clamp. Then I moved the lever to its most rearward position likely to be comfortable for normal use. I measured on center between the two holes and got a figure of 4 7/8 inches. I cut a piece of bar stock 5 5/8 inches long and drilled two 5/16 inch holes 4 7/8 inches distant from one another on center. As before, remove all burrs.
Step 18: Install the Connecting Rod
Cut two pieces of 5/16 inch rod to 11/16 inch each. These will be the pivot points at both ends of the connector between the lever and the movable jaw. Remove all burrs. Insert one of these rod pieces in the 2nd lever hole and slide the end of the connector over it. Weld the end of the round rod to the lever at the hole. See the photo.
Step 19: Add Another Permanent Nut
Place one of the hole squares over the end of the pivot rod for the connector. Squeeze the pieces together and weld the hole square on the end of the pivot rod as in step 16.
Repeat this process for the other end of the connector at the remaining pivot point behind the movable jaw. Weld the short piece of rod to the fitting behind the movable jaw. Weld a hole square over the other end of the round rod protruding through the connector.
Step 20: Mechanism Operational
The mechanism is now operational, although not quite ready to use. Now you can see the reason for offsetting the fitting on the back side of the movable jaw in step 5. The piece that connects the lever to the movable jaw runs in a straight line as it should. The mechanism may be a little rough; but cleaning up welding spatter, lubricating with oil, and working the moving parts back and forth will have it working smoothly very quickly.
Step 21: Drill a Mounting Hole
One 1/4 inch hole and bolt at the very back end of the nutcracker takes advantage of the forces used when cracking a nut and is sufficient. Here you see the mechanism turned upside down for drilling behind the lever's axle.
Step 22: Cut the Base to Length
Cut the base to length behind the mounting bolt hole.
Step 23: Add a Long Handle
I had a piece thinwall electrical conduit that works very well for a handle. With an abrasive wheel I guided one end of the conduit by hand into the cutting wheel to make a slot just wide enough for a tight fit on the upper end of the lever. I ground away the zinc coating and carefully welded the conduit to the lever on both top and bottom. My handle is about 14 inches long. That is adequate, but by no means excessive when dealing with macadamia nuts.
Step 24: 2 X 4 Mount
I mounted the mechanism on a piece of 2 x 4 lumber 18 inches long. I inletted the 2 x 4 so the mechanism fits tightly on it. I drilled a hole through the 2 x 4 for the mounting bolt. I made a recess for a Tee-nut to receive the bolt. I added some extra inletting wherever it appeared moving parts might be hindered by wood from the 2 x 4.
Step 25: How to Use
Place a nut in the jaws where the nut fits when the jaws are fully open. See step 17, right side of the photo, or the photo in the Introduction. Pull down on the handle with a slow, firm pressure. When you hear the shell of the nut crack, stop pulling on the handle. My friend likes to cup his hand around the nut as it is being cracked. It keeps the meat of the nut from rolling away. The photo shows the results when you successfully crack a macadamia nut. The shell is opened, but the meat is not damaged.
Although the jaws for this nutcracker do open far enough to hold a black walnut, I would not advise using it with black walnuts. Use a hammer on those and pick the meats out in pieces. But, this nutcracker would work with properly sized filberts or hazelnuts, Brazil nuts, English or California walnuts, and others,