Introduction: Band Sawn Bowl Ukulele
This instructible will show you how I quickly made a bowl back lute like ukulele from a length of 6 by 1 dar (dressed all round) pine, that's 140 by 19 for those of us in metric land. The trick I am showing off in particular is the use of a band saw to make the back. You might notice there are two ukes made here. I forgot to take a few pictures the first time. Luckily I got in another order pretty quick so a second one was made allowing me to fill in most of the gaps. I also used some pics from earlier builds.
Step 1: Having the Idea
Two of my favourite hobbies are making ukuleles and browsing instructables
Idly browsing I saw this band sawn bowl.
Ok I thought, I have done a few hollowed out ukes and this looks like a good way to make a back nicer and easier than the way I had been doing it.
In particular it seemed a way easier way of doing it than the way I had done it for the Ukulele Underground's two by four challenge which involved glueing up a block of wood, drilling what felt like several thousand 10mm holes and hacking away with everything from spoke shaves and an angle grinder to a small hatchet.
Step 2: Plan a Uke Shape
This shape is a very basic outcome of needing the bridge to be a little bit up the soundboard about half the length of the fretboard needing to be on the neck.
Measuring up from the bottom 70 mm to the bridge
Wanting the body neck joint at the 12th fret and a scale length of 386 puts another mark at 193 mm.
Next mark is where the nut goes 386 mm from the bridge position and if your measurement is on song 193mm up from the body join mark.
Top of the headstock is 120mm up from that.
Vary any of these measurements to taste.
This shape was generated by simply rounding off the bottom by tracing a jar and freehanding a nice curve at the top from the predicted halfway /12th fret. The neck is centered and 46 mm wide at the base and 42 at the nut end - after sanding, trimming straight etc that should come in at around 45 at the base and 40 a the nut end..
Most ukuleles and guitars have the neck - body join at either the 12th or the 14th fret. Ukuleles have a variety of scale lengths that are commonly used
- Sopranino less than 300mm - I tend to build mine at 275mm
- Soprano about 330 mm (similar to Mandolins)
- Concert about 380mm
- Tenor about 430mm
- Baritone (or tenor guitar) 480cm
Interestingly soprano through to tenor are usually tuned the same with reentrant gCEA tuning though it is common for tenor ukes to have linear GCEA - or low G tuning. Other common variant tuning is aDF#B tuning and historically violin/mandolin tuning, GDAE was used a bit but not so much these days.
You can alter the length slightly and shifting the neck to body ratio as long as the bridge does not look in too silly a position. For most people who only play chords in the first few frets a join at the 12th fret is fine.
Step 3: Start Cutting
The first cut, made at about 35 degrees is made about 10mm in from the edge. Because you can not make bandsaws cut central holes easily the cut in to the line is made along the line of the wood grain to make it harder to see. If you have a scroll saw or a sabre/jig saw you can start your cut in the middle by drilling a series of holes and inserting the blade in that.
On the second one I made I switched from my standard 6tpi 6.4mm wide blade to a narrow 3.2mm thin scroll cutting blade. This made getting arround the curves easier but following the straight lines harder. Adjusting all the guides on my cheap bandsaw to go with the narrow blade was a pain in the proverbial.
When the central piece is removed and placed on top the theory of angles tells us it then overlaps by about 13mm (19*tan (35)) minus the bit that the saw cut out (the kerf) which makes about 10 to 11 mm.
Step 4: Trace and Second Cut
Turning that over and attempting to keep things evenly aligned I then traced the line for the next cut into the part on top. In practice I think that line is in about 10 or 11 mm in. Yay math!
For the second cut I increased the angle to the maximum my band saw would allow, about 45 degrees.
Then glue up the two ring like pieces which have a slot in them where the blade went in to cut the ring. One clamp to keep them aligned vertically and one to push the sides in.
Step 5: Glue Hollow and Shape
Now carefully align your shapes, skewing the edge towards the back will create a more tear drop shape when smoothed off. I added a bit of fiberglass drywall tape as cross grain reinforcement just in case. A quick smooth off and removing leftover glue from the previous step might be necessary with a sandpaper block if you are as messy as me.
Roughly smooth off the outside at this stage only enough to reduce the likelihood of splinters. Gently gouge out the inside and sand it to as smooth a finish as you can. I used a 30 mm forstner bit to give myself a bit of a head start on that center piece
Step 6: Thoughts About Adding a Skew
On reflection it is clearer to me now that if you cut the walls thicker at the neck end then the skewing of the joins will be able to be used to create a much more tear drop like shape. this sketch should show you roughly how it should work if you just smooth out the bumps between the valleys.
Be careful though or it might end in tears.
You can also get an idea of how much you can take off the sides by drawing a diagram like this.
Step 7: Hollowing Out the Front
Now that we have the back done now we turn our attention to the front. I like to use a hole drill with the centre point removed. I set the depth stop on my drill press so the hole drill leaves about 6 mm of height and get drilling. After putting in sufficient circles I get out my chisel and knock out the bits I want hollowed out. After that I set the depth stop closer to 3mm, checking it on a piece of scrap and carefully grind out that last few mm. Finish off with the sanding attachment.
I have also used a router and and angle grinder with a sanding pad to do this task on other projects. They both work well if you don't mind living in a cloud of fine sawdust.
If you have a bigger band saw than mine you could simply resaw a slice off the top, stopping at the neck join and then saw out a hollow in the middle. I have done this with a 90 by 19 to make a narrow travel style uke and it worked well for that.
Step 8: Cut Sound Holes
I didst not get a photo of the cutting of the original sound hole but you can see the effect in the later photos. Feel free to get funky with the hole shape it is a great area for personalization. If you are going for more funky shapes a bit of reinforcement on the inside may be in order to prevent ouchies.
Also a good time to fiddle with headstock shapes.
For ukes with tail pieces I have had little problem without adding bracing but if you fancy having a properly glued in bridge and saddle here is a picture of how I braced my other tear drop uke.
Step 9: Glue Together and Cut Out Main Shape
Check the alignment of the pieces one last time. Add your maker's mark to the inside of the uke and stick it together. I like to add a bit more fiberglass drywall tape to give a bit more cross grain stability again.
Carefully cut out the final outer shape of the uke using your bandsaw.
Step 10: Prepare the Headstock and Plane in a Bit of Neck Angle
For a peg through headstock I like to allow 120 mm for the headstock from my nut location, cut a 15 degree angle and glue it together - I like to put in a couple of temporary staples to stop sliding and then clamp tightly.
When dry remove the staples.
I then planed a slight angle into the neck to help create a bit of down force and room for the bridge. I don't go for an angle I trim it at the nut end so it is about 3 mm lower and even with the top where it joins the body. The straight edge (50mm ruler) lines up a with a 3 mm gap where the bridge is to go. Add a 2 or 4 mm for the fret board 1.5 mm for the frets and 3 or 4 mm for the strings to be above the frets and we will need a 10 mm or so high bridge.
After that I glue a couple of side pieces onto the side of the headstock, plane that flat and then a veneer over the top.
Step 11: Glue on Fretboard
I have a home made fret board duplicating jig that uses a commercially cut fretboard as a pattern for me to duplicate the fret locations on a pre-cut fretboard. It is simply made by cutting a U shape made from 3 bits of wood (or 2 bits of wood and a bit of MDF in my case) at right angles and putting a bit of snap off razor knife at the bottom to lock into the frets of the existing fretboard, which ensures that the frets I then cut in the top fretboard duplicate the ones in the bottom. Many fret slotting jigs go to a deal of trouble to ensure the depth of cut is uniform and deep enough for the fret tang. I use the startlingly simple method of stopping when I can no longer see light through the bottom of the saw teeth. The saw I use is a standard dovetail saw. I started out many years ago using a junior hacksaw and you may find a saw you have laying around your shed may do the job. For example I only had to hammer flat the teeth of the regular hack saw blades a touch to flatten the set of the teeth and they worked well too. See the above set of test cuts I made using saws laying around my shed.
One of the magical things about fret boards is that if you start one fret down you have a fretboard that suits a guitar with a length one fret shorter. Most guitarists will be aware of the use of the capo which is a non- permanent application of this principle. In this case I used a standard 648mm scale length 26 fret fretboard given to me by Big Stan at Bilinudgel woodworks https://www.facebook.com/BillinudgelWoodworks By starting at fret 9 I have a fretboard that was a notional 385.3mm scale length.
At the top of the fretboard I make a small recess to put the nut in. All a nut is is a zero position fret which has slots in it to hold the strings in place, but now I have lectured you about capos and how I use the regular fretboard to make my much shorter ukulele one you probably worked this out for yourself already.
Other ways to mark out fret spacing for any length of fretboard are :
The old fashioned way - multiplying by 17/18ths or 1/18 depending which way you go.
The more accurate old fashioned way mulitiplying by the 12th root of 1/2 (or 1 minus it as above) - this gives the same result as the Stewmac calculator.
If you are going to use the fretfind2d page you have to make sure you print your PDF at actual scale because Adobe reader defaults to shrink oversize pages which also shrinks normal A4 size pages. It gives you an accurate scale, just a little shorter than the one you thought you were printing. Double check that double the length between the "nut" and the 12th fret on the printout. If this is half of the scale length you thought you were getting you are good to go.
If you don't quite feel up to buying fret wire, I have used split bamboo toothpicks superglued down and bent 50mm nail gun nails.
Most of these tips I got from the cigar box nation site.
I like to literally drench my fretboards in shellac to help stabilize it and make the grain "pop" particularly when I use reddish hardwood timber decking (eg karri, jarrah, meranti) which though hard has a tendency to split and splinter. Others like to use super glue and most don't bother. This fretboard is from Boral Forrest red, being select Australian eucalypt from east coast forests random species of red in colour, (vs forrest brown) and benefits from the stabilisation.
Here I have added some abalone shell fret dots at the 3 5 7 9 12 and 14th frets, front and sides. There is a surprising amount of debate over whether a dot needs to be at 9 or 10 and 14 or 15. Some ukes get away with dots on the face at 5 and 7 or none at all.
I cut my own using a diamand core drill bit. I have used everything from knitting needles to bbq skewers to screws to pyrography to mark fret positions. These are really just bling for the audience. The side markers are what the player sees.
Step 12: Final Shaping
Now we so some final shaping, cutting the headstock shape and thickness, Check the required headstock thickness against your tuning pegs. Standard ukulele tuning pegs have a 23mm or so shaft requiring a 14mm or so thick headstock. If you have got guitar or mandolin tuning pegs the shaft is usually about 28mm or so, requiring a 19mm or so thick headstock. Add to this the complication that the hole on the shaft might be in a slightly different position or you have bushings to install then you have allow for that as well. Give a little bit of thought as to how the path of the strings is affected by the eventual peg hole placement. Having strings rub against the shafts of the tuner below is a bit of a no no in luthier world.
I started by rough cutting the edges in using the band saw, then used a small block plane to smooth out the flatter areas particularly where the grain is longitudinally arranged. I then pulled out my trusty Multitool and rough disk. A potato peeler to shape the neck and a power sander to smooth things off.
Then sand and sand and sand things smooth by hand (or power tool if you lack the patience). Start with a rough grit, 40 to 80 and work your way up to finer grit.I usually don't go higher than 400.
Double check the fret board is absolutely flat and that the fret slots are all clean and deep enough.
Clean the edges of the fret slots with a small triangular file, which also makes insertion and possible later removal easier. You really should never have to replace nylon stringed ukulele frets. Steel stringed instruments on the other hand may need frets replaced if you play a lot, so if you are using this plan to make a mandolin you plan to use a lot make sure those edges are beveled.
I hammer in my frets using a home made small wooden mallet. I have seen plenty of other ways of doing it.
I file the ends flat by holding my file at an angle of about 30 degrees to the fretboard and filing the bevel on and then smoothing the last of the fret tangs that stick out. Some people prefer to file flush vertically then add a bevel. These people are fools! Don't listen to them.
Then I check for flatness of the frets again using a razor blade as a fret rocker, hammering down any recalcitrants that seem to stick up. any short straight thing will do. Then a quick wipe with my diamond sharpening stone to make them really level. Fine sandpaper on a hard strait block if you don't have a diamond sharpening stone. Lastly I smooth them off with a loose bit of 400 grit sandpaper held in my fingers which also takes care of the slightly sharp edge left by the beveling of the fret ends.
A drop of superglue on the ends of the frets stops them from shifting.
Step 13: Adding a Tail Piece.
Now we sand a bit more and apply whatever finish we desire. This is finished with Feast and Watson Wipe on Poly. My fretboard tip is to not just wipe on but wipe off as well like a good burnishing/Danish oil finish. I like to use fine steel wool between coats. The first couple of coats on pine soak in really quickly so I tend to wait five or ten minutes between my first and second coat and then leave it for more standard waiting times. The main advantage of the wipe on finish is that if you see something you want to change slightly like smooth out a rough bit then subsequent coats of oil will build evenly enough to be almost unnoticeable.
Centering the tail pieces is achieved by using a long straight edge to put two alignment marks on the masking tape you have put at the end of the uke and centering your tailpiece on that. On the first one I used an art deco style hinge that is commonly available in hardware stores around where I live. The second one is based on a picture rail hook that the $2 stores around where I live have. I just straighten them out a bit while puting in a square bend and drill holes for the fixing screw and tying in the strings. Make sure you knock off any sharp edges or the string will just cut loose when you tighten it.
I have used everything from 2 inch galvanized clouts to carved wooden plugs to baked bean tin ring pulls as tail pieces.
Step 14: Add Tuning Pegs and Strings.
Drill holes for your tuning pegs the diameter of your shaft (6mm in my case). Make sure the holes are far enough apart. At least the length of the backing plate apart. I like to keep my first row of tuning pegs at least 40mm up from the nut to give my knuckles room to move.
I use a compass set to 12mm to put pin holes in from the sides. This compass has a blade at one end and a point at the other. The 6mm brad point bit starts nicely in the hole made by the compass point. Make sure you check your tuning pegs against the measurements you will use and how it will look with the backing plates.
I keep the tuning pegs parallel by using any straight thin object to hand.
The nut is just a piece of melamine chopstick. Don't worry if you cant get actual melamine, any hard plastic, bone, wood or metal will do.
The bridge is just an offcut of fretboard wood cut into a wedge cross section about 6 or 7mm thick at the bottom 60 or so mm wide and trimmed to a height where the strings finish up between 2 and 4mm off the fretboard. Lay a ruler down the fretboard to give yourself an idea where to start. I start with the bridge blanks 19mm high (the thickness most of my wood comes in) and trim them down slightly oversize and cut the slots down to the right height. Sandpaper is your freind in shaping and trimming. I use a hacksaw blade to establish the slot positions and then shape them with a half round needle file.
The nut slots are made by measuring about 3 or 4 mm in from the edge and two more evenly spaced between (divide the distance between the two outside marks by 3). The bridge slots will need to be a little wider apart because of the taper of the fretboard. I make the two outside marks by lining it against the body end of the fretboard and marking it a mm or two in. Divide by 3 to get locations for the two middle slots.I tend to use nylon fishing line instead of store bought ukulele strings. I know of people who use monofilament flourocarbon leader line. My recipies for standard gCEA tunings are:
For tenor length 400mm+ or thereabouts 17 inches in the old money
50 80 60 40 lb fishing line
For concert/soprano 360 mm or thereabouts
60 100 80 50 lb fishing line
Substitute wound guitar D string or mandolin G string for low G
For sopranino 270mm or thereabouts with dGBE octave(s) above guitar tuning
40 60 50 30
Substitute 80 or 100 lb line for low D
I paid $3.80 for a spool of Jarvis Walker bulk economy line at Big W about 4 years ago. They had similar line at Kmart for similar prices from other makers. Lately the local stores (far from the ocean) have only been stocking 60lb and lighter.
I use something called a Pitzen knot to tie my strings on but many good fishing knots will do. An overhand loop knot is probably the simplest and is how I used to do it (usually in combination with a larks head knot).
The bridge position is going to be a smidgeon longer than twice the distance from the nut to the 12th fret. This is called compensation, or intonation. It compensates for the fact that when you push the string down onto the frets you are bending the string slightly and making it stretch - hence sound sharp. You can check it by checking the note at the 12th fret is an octave above the open string if it is too high move bridge further away from the nut - if too low move the bridge closer to the nut.
Mark the position of the bridge so when it inevitably gets bumped out of position you can put it back again with comparative ease. If your bridge is keen on wandering a drop of superglue will keep it in place.