Introduction: Make a Ukulele With a Pocket Knife.
First Prize in the
DIY Audio and Music Contest
You can't make a ukulele with a pocket knife they say.
You need hundreds of dollars worth of fancy tools and super special skills and fancy materials they say.
Well you can consign those views to the scrap heap of history. This uke will be built with a pocket knife(and a ruler) using mostly materials you can get from a $2 shop or your recycling bin. The only special materials here are the tuning pegs which can be bought on ebay for about five bucks.
- One 60 cm length of 89 by 19 radiata pine found in shed ($3.78 for a 1.2m length)
- One pocket knife $3.99
- One pack cheap superglue $2.00
- a steel ruler $2.00
- One pack thumb tacks $1.95
- Ukulele Tuning Pegs $4.69
- Some bamboo toothpicks ($2 for quite a few)
- 1/4 sheet of 40 grit sandpaper (48c for a full sheet)
- An empty PET bottle (Type 1 recyclable).
- Ukulele strings (tenor) - or 40 80 60 and 30 lb fishing line ~$10-20 depending on quality. My fishing line was $3.80 a spool.
- A beer bottle cap full of methylated spirits (denatured alcohol) and a lighter.
When buying tuning pegs try to get ukulele tuning pegs and not guitar tuning pegs as Guitar tuning pegs are longer, which may mean they won't work as well in this design. Feel free to substitute wood glue for super glue or staple gun for thumb tacks if you have them in your tool kit or think the kids might superglue their foreheads to the table.
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Step 1: OK So the Pocket Knife Is a Bit of Dud
After removing the pocket knife from its clamshell packaging, the blunt state of the saw blade was revealed. A bit of work with a triangular file was required to make it cut wood at all.
Step 2: Proceed Regardless and Measure Up
OK so the knife is a little dodgy but we will soldier on. A little measuring/ just sticking stuff down and I work out how much space I need for the tuners, allow about 415mm for the scale length, put the neck to body join just a little further than half that towards the bottom from the nut so I can have 12 frets to the body, giving me an octave to play with - an admirable number of frets for a ukulele. For most people, when playing, using any more than 5 is just showing off. I can probably get by with 3.
The width of the neck at the nut is about 40 mm and the width at the body is about 45 mm, giving us an attractive taper.
Step 3: Cut Out Your Shape
Cut out the shape now.
Unfortunately, even after sharpening that poor quality little pocket knife was still not cutting very well so I cheated a little by looking in my bike saddle bag and conscripted my super cheap copy of a leatherman into saw duty.
The awl attachment on the pocket knife only needed a little sharpening to make a great little drill to start off the cut out. The hole is then enlarged in the direction you want to cut, using the knife, until you can get the saw blade in. Cutting around corners and tight curves is a bit tricky but is achieved by repeatedly going back over the gap and widening the slot till the blade gets round the curve.
You can get a little creative with the shape of your hole as long as you remember to keep a bit of structural integrity, especially around the neck join and at the tail.
Step 4: Thin the Headstock
Now's the time to create a head stock to the length of the tuning pegs, which is about half an inch, or around 12 mm. To be sure I had enough room I didn't bother measuring but held the tuning peg against the side and drew my guide line according to that. My ruler tells me that I actually finished with a thickness of 14mm.
There are a few ways to do the actual thinning down. You could just accurately cut down the guideline but this is hard enough to do with a decent saw. Similarly you could just sand it down. Getting it to join Jenny Craig is probably not an option.
My simple solution was to make a few shallow cuts down into the face of the headstock and snap off the thin left over bits using the bottle opener attachment and cut the stubborn bits off with the knife or saw.
To help with the task of shaping and smoothing I made a sanding stick by wrapping a quarter of a sheet of sandpaper round one of the side off cuts and pinning it in place. I hear a rumour that they make sandpaper finer than 40 grit but we should not be needing that.
Sand the remainder of the headstock flat.
Step 5: Increase Wiggle Room.
The physics of getting a flat stretched membrane to vibrate freely means that we need to create just a little room between where or membrane is going to be and the part that is supporting the membrane. This is easily achieved by sanding and scraping a slight slopes, hollowing out the inside.
Step 6: Holey Headstocks Batman
Mark out your headstock making sure you are going to have enough room to get them all to fit next to each other and above each other. Measure the width and length of the backing plate and as long as the holes for the ones beside each other are more than the width and at least half that in from the edge, plus the two rows of holes are more than the length of the backing plate apart you should have few problems.
The marking out was the hard part. This sharpened awl attachment makes short work of headstock holesmanship. I even managed to be careful enough to notice when the point was about to break through and turned it over and finished the hole off. This prevents accidentally knocking a large chip of wood out of the back.
After such a nice result with the holesmanship it was just a pity the hole was not big enough. Never mind, the fish scaling tool was just the thing I needed to make the hole just that little bit bigger that I needed. Maybe the nail file attachment would have been just as good but for now, the job is done.
I hate to be picky but there is nothing more mildly annoying than mid mounted Phillips head screwdriver tools on these pocket knives. The person who thought of putting them there should be given 200 screws to drive in with one, with the added complication of being 15 mm from an inside cupboard corner. I only had 8 screws but I found it annoying enough to cheat slightly and go back to the cheap leatherman copy for a few minutes.
Try to get ukulele rather than guitar tuning pegs for this design as guitar tuning pegs are made for thicker headstocks and you may not get enough break angle initially over the nut. This would be fixed by:
- padding the back with whatever is handy (from mahogany verneer to paddle pop sticks to layers of cardboard) to lower the post as it sticks out of the top,
- drilling an extra hole in the post (not really an option for the pocket knife builder) or
- using a bit of wood or metal with a screw to push the strings down before the nut. The formal name for this arrangement is a string tree.
Some tuning pegs come with collets or gromets that require a hole with 2 widths. This is relatively easy if you are using a power drill but much more difficult if using a pocket knife so take note when buying.
You may notice the neck is supported by the sanding block while I screw in the tuning pegs. This is because the ends of the tuning pegs would otherwise hit the table and push them out slightly.
Step 7: Nutty Little Thing
Just now I took the sanding tool I had made, marked the width of the neck at where the nut is to be and then add the width of my finger and cut a short length to make the nut and bridge from. I could have used one of the other offcuts but this was at hand.
I then cut a smallish squareish bit and cut it to length and glued it on as the nut.
Sand everything down, flat and straight.
Just to make things look better and last longer I smear on a layer of super glue all over the uke. This is a relatively quick and convenient varnish.
Step 8: Fret Over the Frets.
Frets are a way to make strings shorter so that in theory when you press a the string down on a fret the string will sound the number of semitones higher than the open string that you have pressed the fret down at. A lot of clever people have worked out the the theory of frets and if you are so inclined feel free to google it. In the interim I googled fret calculator and used the one on the Stewmac website to work out the fret spacing for a 415 mm scale on a ukulele.
Here are the measurements
415.000mm fret scale
fret from nut
Because I am working on a tenor scale length which is a little forgiving and I am doing this purposely on the cheap I am using the steel ruler to measure and mark where my frets should go. I have probably only been accurate to within a half a mm. This means I will be out of tune by 0.5 divided by the distance between the frets, expressed as a percent. At the top the frets start at around 23 mm apart, making me possibly 2.5 cents out of tune. At the 12th fret, the frets are around 12 mm apart, making me possibly 5 cents out of tune. Given how bad I play I can live with those numbers.
The marks go a little way down the side so that I can see where the frets are supposed to be when I put them on the top.
The frets are made by splitting bamboo toothpicks using the blade of the pocket knife and snapping them to a slightly long length that will be sanded to the right length later. Try to keep them a uniform size to minimize the work required to level them later. Scrape the back of them flat using the knife blade if needed.
Firstly I use a tiny amount of super glue at either end of each fret. A small amount of super glue will set quickly and be easy to slice off if you see any obvious mistakes a long the way. This means use fingers instead of clamps and you can move surprisingly quickly. Once all the frets are on, take a good hard look at them all and convince yourself that none of them are in the wrong spot. Fix any that are in the wrong spot.
Note how I put a sheet of cardboard down to stop getting super glue all over my concrete table
Go over the frets with more super glue to harden them and to stick them down more securely. Now make sure they are flat with your ruler. The edge of my ruler was surprisingly sharp so I was able to flatten a couple of high frets using it as a scraper. I then rounded over the flattened fret by scraping with the knife blade.
If your budget stretches to finer sandpaper you might like to make yourself a torture board by gluing some of that to nice long piece of straight flat wood so that you can flatten the frets properly. Nothing fancy - just lay it down over the top and flatten.
Now just sand back the ends of the frets and shape the neck a little, I just took a little off the corners around the back of the neck on this one, smearing around some more super glue as a quick and convenient varnish.
At this point I also added some pencil marks for the fret dots. Because I had coated the uke with superglue I had to put a drop of super glue on top of the pencil mark to stop it rubbing off. These are just marks to help you see where your fingers are on the fret board. Feel free to get creative.
If you haven't used the super glue as a varnish to this point you might like to think about varnish or paint of some sort now.
Step 9: Tack on Your Membrane and Obtain the Blessings of the Fire Gods
I embarrassed myself a little as the 1 liter PET bottle I had was too small and the milk bottle refused to shrink when I heated it. Always test an off cut of your bottle to avoid floppy tops.
A slightly larger 2.25 liter bottle was rescued from the recycling bin, cut up by cutting off the top and bottom and then slitting once down the side. The bottle then unrolls to quite a large size. Then secure to the top of the uke using thumb tacks along the sides. The tacking over beside the neck looks like over kill but on a previous prototype I left it unsecured along that edge and found I got a lot less tension and volume into and out of the top. On this one I gave it a bit of a trim before I did the shrinking. The scissors on this pocketknife are seriously sub standard.
If you are of a neat mind you may wish to use your ruler and pencil to measure and mark out even spacings for the centers of your thumb tacks so they line up neatly and look tidy. Or you can be like me and just keep putting them in every thumb width or so.
To obtain the blessings of the fire gods on the ukulele I used a small metal container (a beer bottle cap) filled with methylated spirits (denatured alcohol) lit on fire. Just take things nice and smoothly try to shrink the plastic, not melt it, or set it on fire. Feel free to invoke the fire god or goddess of your choice. Pele the Hawaiian goddess of volcanoes would be a good choice though Hephaestus (Vulcan for you Romans) the Greek god covering blacksmiths and artisans would work just as well.
Any source of heat from a camp fire to a hair dryer to pouring boiling water over it should work. The membrane should now be tight as a drum and should sound like a drum when you tap it (wait till it cools a bit first).
Step 10: Build a Bridge.
The bridge needs to be a small triangle of wood the height of which should be around 10mm. To this we add 4 string notches, the outside ones are set at a width just inside the width of where the neck joins the body. The middle two you work out by dividing the distance between the outside marks by three. These are about 12mm apart. Add super glue to harden and strengthen. I also made a small arch in the bridge by sanding out the middle of the bottom a bit.
To make string anchors I placed the bridge in the middle on the back and marked the spots for two screws half way between the outside pairs of string notches. In the past I have used decorative hinges and other things like bent keys or ring pulls of baked bean tins as string anchors, or to give them their proper name, tail pieces. Baked beans truly are the musical fruit.
Notches are cut in the nut as well.
Step 11: String Er Up
I have strung this one with 50 80 60 and 40 lb fishing line for standard gCEA, or in smart phone tuner parlance G4C4E4A4 tuning. I use DA tuner on my android smartphone as my tuner. Alternatives include using mandolin strings and tuning or 20 or 30 lb fishing line and Tahitian tuning, which is gceA, or G4C5E5A4, which is the same as standard ukulele tuning except the two middle strings are an octave higher.
There is no set length that manufacturers use for standard ukulele strings but they will almost certainly be too short for this plan. Tenor ukulele strings might work. If you buy a set of ukulele strings you will need to work out before you start if they will fit or if you can make them fit by using a hinge or something like that as a tail piece. You may need to shorten the scale length and the body.
Simple overhand loop knots are tied in the end of the strings and they are hooked over the screws in the back.
You may notice the strings are wound in whichever direction is most convenient for keeping in line with strait notches in the nut. The two outside strings are wound in the opposite direction to the inside strings.
The bridge is placed just a smidgen further from the 12th fret as the 12th fret is from the nut. This can be tested by playing a note open and then playing a note with your finger on the 12th fret and looking what happens on your tuner or smartphone tuning app. If the two notes are exactly an octave apart you are laughing. Otherwise shift the bridge slightly till it is right. This is called adjusting the intonation.
Now we have the strings on we can fine tune the action by cutting the nut slots deeper or filling them with super glue if you go too far. The height of the strings from the first fret is about a half a mm. As long as it is close and does not actually touch you should be fine.
The bridge is lowered by sanding the bottom off it or deepening the notches.The height of this bridge is around 9 mm and the height of the strings at the 12th fret is about 4 mm, which is a touch high but given I am playing with slightly uneven bamboo toothpick frets and the membrane is not held that tight to the body this gives me some leeway in making sure all the frets do their job and give me a bit of time for when the frets wear down before they start to buzz. On a uke with metal frets I like the action at the 12th fret to be around 2mm.
If you feel like taking the time to readjust the bridge position a little because by lowering the action we have altered the required intonation go right ahead . It pays to make a mark where the bridge is supposed to go as it can be knocked out of position relatively easily.
Step 12: Coda: Play It and an Extra Lesson on Knife Purchasing
Now you play it. It will take a little while before it settles down and stays in tune but persevere with it and if one string refuses to stay in tune it may pay to restring it and make sure the tuner is working properly. The fishing line I use takes a half an hour to settle down at first and then just slips/stretches slowly for a few weeks after that, losing a semitone a every couple of hours at first and then the period taken to lose a semitone stretches to a day or so.
Just as a side attempt to establish if all cheap pocket knives were as bad I went into Kmart and bought a very slightly different one for $3.50 - 50cents cheaper than the first one. The Kmart one has a much more useable saw blade and scissors but still needed the awl to be sharpened. You do not always get something better by paying more. In the end a swiss made one would have been much better.
Be careful of things in clamshell packaging.
If I have a criticism of this Ukulele it is that it is extremely light which makes it move about a bit when playing if you have a hankering to play bar chords especially as the ukulele likes to move along with you as you slide your fingers up and down the fret board. To address this, you might like to attach something with a bit of weight to the back of the ukulele. Maybe a rock or some heavy metal ;) On the other hand the lightness does make it great for backpacking.
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