So Grace wanted a nutcracker. I could have walked down to the shop and bought a cheap one for a few pounds...
But why would I want to do that when I can spend several hours and several times the cost to build our own?! I recently saw one of the screw types for the first time and thought, "What a cool idea. I could make that..." So I did.
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Materials
Early on I decided to use aluminium. It's relatively cheap, easy to machine and it doesn't rust. I came across a chunk that was about 3 1/2" in diameter and 1 5/8" long that would be ideal. The Tommy bar would be mild steel and I'd use a short length of studding for the screw.
Step 2: Facing Off the Body
The aluminium body was chucked in the 3-jaw and faced off. Then it was flipped end for end and the other side was faced off.
Step 3: The Boring Part
Next a pilot hole was drilled through the centre. I started with a centre drill followed by a 3mm, then worked up to my largest drill, a 3/4".
Then I bored out the starter hole with a boring tool:
Once I had enough clearance I switched to my larger boring tool. This is a home-made jobby with an HSS tool bit secured in the end of it:
I bored the hole out to a diameter of about 2". We guessed that 2" would be enough to comfortably fit a walnut in the bottom, and aesthetically it would look ok. Many, many miles of swarf later, we had this:
Looking at the last few photos, you can see a mountain of ally swarf building up around the lathe!
Next I took a light skim off the outside diameter just to tidy it up a
little. I didn't get a photo of the set-up, but I did it by opening the chuck jaws inside the bore to grip it from the inside. I wasn't too confident about the whacking great lump of ally staying put while it was gripped like this, so I ran a long length of studding through the headstock bore. I placed a metal bar clamp over the end of the studding and the end of the ally, then nutted the studding at both ends. This pulled the ally in towards the chuck and made sure it wasn't going anywhere (I used a similar method again later to mount the ally on the crosslide). To make sure I didn't mark the surface of the ally, I put a few sheets of paper between it and the clamp.
Step 4: Milling the Bottom
Though the wheel may be a marvellous invention, it doesn't make a practical nutcracker! To prevent it from rolling all over the table instead of cracking nuts, I had to mill a flat onto the bottom of the ally. I secured the ally to the crosslide by using the same bar clamp from before plus a bit of studding. Then I milled the flat using a fly cutter. Note the paper again to stop the clamp from damaging the surface of the ally:
Step 5: Dilling the Screw Hole
Now I had to drill and tap the screwhole at the top. This obviously had to be in line with the centre of the milled flat on the opposite side. To mark out the position I clamped the flat bottom to a vee block, although an angle plate would have worked just as well. This ensured the flat was perpendicular to the surface plate, and therefore the axis for the hole would be horizontal and running through the centre line of the ally's diameter. Then I set the height gauge to half the diameter and marked the position:
I drilled the tapping hole with the bench drill. I can't tap straight for toffee, so I tapped the hole using the drill chuck (off power of course!) while the ally was still in position. One day I am going to build a dedicated tapping fixture for jobs like this.
Step 6: The Tommy Bar
That's the main part of the nutcracker finished. Now for the Tommy bar.
I faced off the end of some 3/4" steel bar to make the "hub" of the Tommy bar. Rather than cut it to length straight away, I worked on the end of a long bar to make the cross drilling easier. This means using a fixed steady to support the end of the bar.
With the bar faced off, I marked out the position for the cross hole,
then set it up on the bench drill. There are many ways to cross drill round stock (most of them awkward) and I used the method that I found easiest with the kit that I've got. I clamped the bar in a small machinist's vice. To ensure the hole position was exactly perpendicular, I placed a small square on the drill table against the bar. Then I measured across and made sure the hole position was at 3/8" (half the diameter of the bar). It's pretty much the same method that I used on the nutcracker body, but flipped 90 degrees. Then I lined up the hole position with the drill and clamped the vice down:
(I forgot to take these photos at the time, so I staged them afterwards with a fresh lump of bar. That's why the end of the bar looks like it's been chewed by Richard Kiel) I drilled and tapped the hole straight through to take the arms of the Tommy bar. At either end of the hole I drilled a shallow counterbore the diameter of the arms. This is to allow an un-tapped portion of the arms to sit inside the hole. If I didn't do this then the tapped ends of the arms wouldn't sit fully in the hole and it would look untidy.
Step 7: The Tommy Bar Hub
The "hub" was then sawed to length and the sawn end faced off in the lathe:
Then it was drilled and tapped to take the main screw of the nutcracker (some M10 studding). I could have made the screw and hub all from one bit of steel, and screw-cut the thread, but as I already had some studding to use...
When I'm tapping or using a die in the lathe, I use a spindle driving handle to turn the chuck. My handle was built from a Hemingway kit, and I find it makes tapping on the lathe far easier.
Step 8: Ends of the Tommy Bar
Next I made the ends of the Tommy bar. These are simply a bit of 1/2" bar, faced of both ends, then drilled and tapped one end to fit the Tommy bar arms (here pictured next to the hub):
Step 9: The Tommy Bar Arms
Finally the arms were made by cutting a thread on the ends of some 1/4" bar. I used a tailstock die holder for this:
And the assembled Tommy bar:
Step 10: The Anvil
As mentioned before, the screw was just some studding. Grace decided that the screw needed something a bit more "industrial" on the end of it for crushing nuts into oblivion. So I made an anvil of sorts using some more 3/4" bar, and this attaches to the main screw with an M4 screw. The anvil needed a 4mm clearance hole drilled through it, then a counterbore to house the screw head. I don't have any "proper" counterbores, so I just used an ordinary 7mm drill. This leaves the counterbore without a flat bottom which isn't ideal, but in this case it's not going to matter. As before, I found it easier to work on the end of a long bar then part it off to length.
Step 11: Assembly
All the parts are then assembled together and held in place with some locktite.
And finally the finished, assembled nutcracker showing some walnuts no mercy!
Runner Up in the
Homemade Gifts Contest