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You can get me at:
matt (at) hairybrain (dot) co (dot) uk
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A Custom Espresso Tamper Handle
What the hell is an espresso tamper handle?
As far as I can tell, it goes like this: the process of making espresso involves forcing hot water under high pressure through a wad of finely ground coffee beans. These have to be squashed ("tamped") into place with care, so that they're evenly compressed into a nice smooth symmetric puck of coffee. Otherwise, the hot water won't flow evenly through the ground beans, and this results in a sub-optimal espresso. The tamper is a hand tool that a barista uses to compress the ground beans.
Now, I was recently asked to make a custom coffee tamper handle which would screw into a Reg Barber tamper base. This is a wooden knob which screws onto the base, which is a disc of stainless steel with a recess and a threaded hole to accommodate the handle. The handle was to be a present for a barista whose nickname is "Kingseven", so it was to be shaped like a king from a chess set. For added king-themedness, I decided to make it out of Brazilian kingwood. It's convenient that kingwood is one of the most beautiful and exclusive woods in the world. It'd be a pity if there was a wood called kingwood but it just happened to be that shitty bendy stuff you get in Homebase. Anyway, making this thing turned out to be an interesting process - and so here we are!
Reg Barber tamper handle specs
.jpg) | | A sample handle - the bottom of the custom handle has to be identical to this one, so that it fits the tamper base properly |
So here are the specs of a Reg Barber tamper handle, as far as I can make out: the handle has a flat bottom with a diameter of 30mm and 6mm of 3/8" x 16tpi UNC (Unified National Coarse) threaded rod (actually a socket drive set screw) sticking out of it. I suppose it could be a BSW (British Standard Whitworth) thread - the difference being that BSW uses a 55 degree thread angle and UNC uses 60 degrees. This would matter if I was making parts for, say, a spaceship or a particle accelerator or something, but for a coffee tamper, bodging slightly incompatible threads together is probably not going to endanger anyone's life (fingers crossed). If the coffee tamper ever gets used aboard a spaceship or in the kitchen at CERN or something, well, we'll worry about that when we have to.
How to make one
.jpg) | | The aluminium handle-holding jig. Note the tapped hole in the top and the dovetail on the base |
Now, making the top half of a king is all very well, but then you can't hold it properly to drill and tap a hole in the base for the threaded nubbin. So here's the trick: put the threaded nubbin in first and use this to hold the piece while turning the top. For this we need an adapter which allows a tamper handle to be held by the screw - essentially a base which can be held securely in the chuck of the lathe. That's exactly what this thing is.
This is a bit of aluminium round bar on which I've turned a 30mm spigot on the top; in the centre of the spigot I've drilled a hole and tapped it 3/8" by 16tpi UNC. The dovetail on the bottom has been turned to fit snugly into the standard dovetail jaws on my Vicmarc VM120 woodturning chuck. Incidentally, the VM120 is a fantastic chuck - better than a Teknatool Supernova and better than a Sorby Patriot. Get one. (Or if you have a smaller lathe, get the 4 inch VM100).
.jpg) | | The jig sitting in the chuck of the woodturning lathe, with one of the jaws removed to show the dovetail fit |
Here's the jig siting in the jaws of the chuck. I've removed one of the jaws to show the fit in the dovetail. The jig is held square by the shoulder above the dovetail, which sits against the faces of the jaws.
Preparing the blank
.jpg) | | Roughing the blank between centers |
First, we need to rough the blank into a cylinder between centers. This is totally routine. Interesting fact: I'm using a Robert Sorby Steb Drive in the chuck. A Steb Drive won't quite fit in a VM120 by default (they're designed for the Patriot and compatible chucks, like the Supernova) so I had to turn mine into shape on an engineering lathe. No biggie.
.jpg) | | Turning a spigot onto one end of the blank |
Next step - turn a spigot onto one end of the blank. This will be held in the chuck of the engineering lathe while the other side of the wood is prepared to become the base of the handle.
.jpg) | | The blank, after facing, drilling and tapping |
Here's the blank mounted on the engineering lathe after facing the end, drilling it to 8mm and tapping it. The tap is held in the tailstock purely as a convenient way to hold it square, essentially using the lathe as a large tap-holding jig - the tapping is best done by hand, not under power. A nice thing about very hard tropical woods like kingwood is that they respond very well to machining techniques - click on the picture to see the large version and you can just about make out the nice crisp threads in the hole.
.jpg) | | The blank mounted on the jig and ready to be turned into the finished handle |
And here we have the blank mounted on the jig, supported by the tailstock. This is done by screwing a grub screw about 3/4" into the threaded base of the blank and screwing the remaining 1/4" into the jig. Essentially this is exactly the same as using a screw chuck. The grub screws I'm using are A2 stainless 3/8" by 16tpi UNC socket drive set screws, 1" long. For now, the screw is not glued into place in the wood. The only real reason for this is that the screws are quite expensive and if something goes wrong when turning the blank, it's handy to be able to recover the screw easily.
Turning the handle
.jpg) | | Halfway through turning the handle |
.jpg) | | Turning complete...now to cut the cross patteé on top |
Turning the handle is a standard woodturning exercise, the only really interesting bit being that making half a chess piece feels a little confusing! Normally when turning a king (or indeed any piece) I work from the base upwards, and several elements of the base give me my cues for the dimensions and proportions of the rest of the piece. So the top-down approach feels a little odd.
In the second picture, note that the base of the handle has been turned to the same diameter as the spigot on the jig, i.e. 30mm. This helps to ensure that it will screw snugly into the recess in the tamper base. Accidentally touching the woodturning tool against the jig is a risk here, but not a big one - it won't harm the tool because high speed steel is perfectly capable of cutting aluminium. The only real problem is that it could damage the jig.
And there we have it!
.jpg) | | The finished handle, with the original Reg Barber handle for reference |
After turning, the piece is sanded and polished. I sand with grits 120, 150, 180, 240, 320, 400, 600, 1000 and 1500, occasionally reversing the lathe so the grain is sanded in both directions - although kingwood is so close-grained and dense that this probably isn't necessary. For softer, more open-pored woods like padauk, reversing the lathe for alternate grits really helps. After this sanding procedure the wood is silky smooth and shiny. Then I apply shellac and burnish it at high rpm using an oil-lubricated cloth. A coat of beeswax/turpentine paste on top finishes it off and provides an extra layer of protection.
Next the cross has to be cut. This is another standard bit of woodwork - saws, chisels, files, sandpaper, elbow grease. Since this is essentially a hand tool I made the cross quite chunky, because a thin, delicate cross would be very easy to break. For this same reason, the collars around the trunk and under the head of the king are quite small and stubby instead of being wide and thin. After cutting and sanding, the cross is (more or less) French polished - shellac and oil on a cloth and lots and lots of rubbing until it comes up nice and shiny.
The final stage is to glue the screw in. You mix up some epoxy resin and stuff it into the threaded hole, grind some threads off the grub screw (this makes the grub screw asymmetrical, giving the glue irregularities to "bite" into, so that the screw will be well and truly locked into place) and screw it home, taking care that it sticks out exactly the same distance as the screw on the reference handle.
And there we are - a Reg Barber-compatible handle. A photo of the handle screwed into a base would be ideal here, but I don't have a base because I don't have any proper coffee-making equipment! But with my funky aluminium jig and lathes and saws, I have something even rarer: coffee-making equipment-making equipment.
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