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Concert Ukulele (The Acacia model neck is pi$$ed!)

This is where we don't want anything but evidence of your finest wood butchering in all its glorious, and photograph laden glory. Bring your finished products or WIP's, we love them all, so long as there's pictures, and plenty of 'em!

Re: Concert Ukulele (Closing the box.)

Postby spb » 23 Apr 2021, 17:11

Any tool will twist under torque, just as any beam will sag under load; it's just a question of degree and whether it's elastic or plastic deformation.

In simple terms, a tool made from the same material, at the same torque, will twist the same amount per unit of length - if it's twice as long, it'll twist (reversibly) twice as much, but that doesn't mean it'll fail earlier or transmit less force to the fastener.

In more complex terms, the shear stress at any given point in a shaft under torsion is determined by the torque applied, the radial distance of that point from the centre, and the polar moment of inertia (determined by the cross-sectional shape of the shaft). None of those depend on the axial length. Since it's stress that determines the yield strength of a material, the length doesn't actually matter* when determining when a tool like this will fail. Since (up to the elastic limit of the material) stress and strain are proportional, that means the shear strain also depends only on those things. It's the conversion from strain to degrees of rotation that depends on the axial length. So, it'll twist more in absolute terms, but still transmit the same torque along the whole length.

*In theory. In theory, theory and practice are the same. Don't sue me if it isn't.
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Re: Concert Ukulele (Closing the box.)

Postby Malc2098 » 23 Apr 2021, 17:45

OK..... I think. :)

I'll see if I can find a cheap one on Amazon and try it out.
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Re: Concert Ukulele (Closing the box.)

Postby novocaine » 23 Apr 2021, 18:00

Ill see if I've got a 4mm bit in the shop that i can weld to a bit of bar for you. Leave it with me.
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Re: Concert Ukulele (Closing the box.)

Postby Malc2098 » 23 Apr 2021, 18:02

novocaine wrote:Ill see if I've got a 4mm bit in the shop that i can weld to a bit of bar for you. Leave it with me.



Cheers, Dave. That's good of you, thanks.
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Re: Concert Ukulele (Closing the box.)

Postby Malc2098 » 23 Apr 2021, 18:07

Dave, if you could make one long enough for a guitar, I'd be happy to pay for postage and a donation to your charity of choice.
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby Malc2098 » 25 Apr 2021, 21:27

I took the bodies out of their moulds and trimmed off the overhang and sanded to sides square to the top ready for the anxious time of cutting the rebates for binding.

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I had also marked out the theoretical bridge locations and covered them with low tack tape.

I decided on black binding for the Acacia, and white for the Sapele.

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I then scraped a back and edge of the plastic binding in preparation for its rebate, and I tried a rebate cut on some scrap wood.

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This is the other setup I have for binding rebate routing.

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I hate this part of the job. It did not go well.
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby NickM » 25 Apr 2021, 21:56

What went wrong?
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Re: Concert Ukulele (Closing the box.)

Postby novocaine » 26 Apr 2021, 07:32

Malc2098 wrote:Dave, if you could make one long enough for a guitar, I'd be happy to pay for postage and a donation to your charity of choice.


Hi Mike
Only just seen this.
not sure you'd need one for a guitar surely? unless you are planning on making one without a sound hole?

found a 4mm bit, found a 350mm bit of high carbon steel but it's 8mm. not put the 2 together yet, how about I weld a bit to the other end, that way you can make it any size with an extension piece.

how big of a hole are you willing to put in the tail?
1 last thing, can you not get in with a flexidrive?

https://www.toolstation.com/quick-chuck ... 86EALw_wcB

you'd need to protect the edge of the sound hole (bit of hose pipe) but seems a more practical solution.
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby novocaine » 26 Apr 2021, 07:33

Carbon fibre is just corduroy for cars.
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby Malc2098 » 26 Apr 2021, 10:53

Dave, thanks for all your efforts.

I eventually found a 350mm tee handle 4mm hex key on Amazon, and my wife bought it for me! :) (She has Prime). So I am fixed up for bolting ukuleles.

I don't propose any guitars with asymmetric or offset sound holes, but I'd prefer not to keep putting hand and tools into the soundhole, when a long tool can be put through the endpin hole. I've ordered a supply of ebony endpins and will measure them when they arrive. I think they'll be in the region of 7mm if I recall correctly.

EDIT. I got a flexidrive and it is too stiff and the radius needed could not be achieved.
Last edited by Malc2098 on 26 Apr 2021, 11:01, edited 1 time in total.
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby Malc2098 » 26 Apr 2021, 11:00

NickM wrote:What went wrong?



You're fighting against the rotation of the cutter all the time. Whereas on a router table, the workpiece is pressed hard against the table and the fence, here, I can only press against the bearings and the washer, and I have to rotate the workpiece at the same time as moving it past the cutter. And I have to try and manage climb cuts, too.

It was a dogs dinner! But the long side of the rebate was ok, it was the short side/long edge that was a mess. I got the body in the vice and stared using a flat file to even it out around the body and and dry fitted the binding and have left it overnight. I'll check later to see how many gaps there are that need smoothing further.

Last year, when I made the Martin 12 String, I made a contraption that hangs the router counterweighted from a vertical track. I had problem or two with that, but I think I will set that up for the second body.
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby novocaine » 26 Apr 2021, 12:34

I usually do binding with a pattern follower bit which has a smaller bearing on, I'll grab a picture this evening. because you've got an arch you will have to work out a supporting base.

I've become fond of no binding for some reason. ;)
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby Malc2098 » 26 Apr 2021, 15:22

The rebate bearing cutters can only give you specific thickness of cut, the difference between the cutter radius and the bearing radius. Buying purfling and binding as a hobbyist, you only get what you can buy, which isn't always the same as the commercial rebate cutter.

If I was clever with veneers, I could make my own binding and purfling at a thickness to match a cutter.

I really like the look of binding and purfling on an instrument. I was really pleased with the result on the 12 String which, hanging on the wall here, looks as good as my 50 year old Epihone hanging next to it. I just wish I was better at fitting it.
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(224.92 KiB)



The T bar hex key has worked brilliantly. Right tool for the job. I could do with one for guitar lengths. 7mm is the width of the endpin hole.
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby novocaine » 26 Apr 2021, 15:52

guess I'm a sneaky git, I have a few different sizes of bearing and may have been known to make a bushing that sits over the bearing to give me the size I want. :)
the katsu came with a clever little guide that sits over any cutter and acts as a guide. I've not really used it as you'd have to keep the router in the same orientation for it to work.
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby NickM » 26 Apr 2021, 16:48

Malc2098 wrote:
NickM wrote:What went wrong?



You're fighting against the rotation of the cutter all the time. Whereas on a router table, the workpiece is pressed hard against the table and the fence, here, I can only press against the bearings and the washer, and I have to rotate the workpiece at the same time as moving it past the cutter. And I have to try and manage climb cuts, too.

It was a dogs dinner! But the long side of the rebate was ok, it was the short side/long edge that was a mess. I got the body in the vice and stared using a flat file to even it out around the body and and dry fitted the binding and have left it overnight. I'll check later to see how many gaps there are that need smoothing further.

Last year, when I made the Martin 12 String, I made a contraption that hangs the router counterweighted from a vertical track. I had problem or two with that, but I think I will set that up for the second body.


I see. Sounds like a nerve-wracking job to me. I can understand why you don't like doing it! I'm sure you'll manage to fettle it to the point where it looks great.
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby Malc2098 » 26 Apr 2021, 17:09

novocaine wrote:guess I'm a sneaky git, I have a few different sizes of bearing and may have been known to make a bushing that sits over the bearing to give me the size I want. :)
the katsu came with a clever little guide that sits over any cutter and acts as a guide. I've not really used it as you'd have to keep the router in the same orientation for it to work.



My Makita has a similar guide. I suppose it wouldn't really matter if the top and back are exactly 90 degrees to the sides, but in the case of these instruments, only the tops are. The previous guitar even had the topped dished. So if you you use the router base on the top or the back of the instrument, then the cutter is going to be at an angle. That's why I've tried to make and use these jigs, just to keep the cutter co-planar (is that the word?) with the sides as it travels round them.
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby novocaine » 26 Apr 2021, 18:26

I have to admit I've only ever done it on electrics, worst case if you screw it up there is a thin line rather than a guitar shaped tool box. :)
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby Malc2098 » 27 Apr 2021, 13:41

I forgot to give the face edges a quick coat of sanding sealer to stop any glue absorbing into the wood faces. hey ho.

I glued the binding on, held fast with lowtack tape and let it cure overnight. Never a pretty sight.

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Here's what it looks like this morning before any cleaning up.

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I'm currently in the middle of cleaning up, using cabinet scraper, HD Stanley blade and 240 grit mirko. It's coming out better than I first thought it would.

But I have to find another way to cut the rebates that is less stressful. I might have to invest in the proper tools, if I want to make more instruments.
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby NickM » 27 Apr 2021, 15:14

It's going to look brill!
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby novocaine » 27 Apr 2021, 15:27

NickM wrote:It's going to look brill!


I'd say it was BOUND to. :D
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Re: Concert Ukulele (Box closed. Prepare for binding)

Postby canoemoose » 27 Apr 2021, 18:03

Malc2098 wrote:But I have to find another way to cut the rebates that is less stressful. I might have to invest in the proper tools, if I want to make more instruments.


I'm coming at this with exactly zero experience of instrument making, but to me this sounds like an ideal application for a router in a pantograph/parallelogram arm. This would hold it plumb but allow it to move in a vertical axis, and then with an edge following bearing to locate horizontally against the body and a single contact point on the base to locate vertically against the body you could follow the edge of the guitar, no matter whether the top was flat, concave or convex. Think of an anglepoise-style lamp arm, but with a router at the end of it with a small custom base.
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Re: Concert Ukulele (Binding (and damage) Cleaned Up)

Postby Malc2098 » 27 Apr 2021, 20:17

canoemoose wrote:
Malc2098 wrote:But I have to find another way to cut the rebates that is less stressful. I might have to invest in the proper tools, if I want to make more instruments.


I'm coming at this with exactly zero experience of instrument making, but to me this sounds like an ideal application for a router in a pantograph/parallelogram arm. This would hold it plumb but allow it to move in a vertical axis, and then with an edge following bearing to locate horizontally against the body and a single contact point on the base to locate vertically against the body you could follow the edge of the guitar, no matter whether the top was flat, concave or convex. Think of an anglepoise-style lamp arm, but with a router at the end of it with a small custom base.


You're absolutely right, Matt. This is an example of a homemade one.

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(78.17 KiB)


And there are other types and methods that keep the router shaft co-planar with the guitar sides. My tiny workshop is filling up with jigs I made last year for the 12 String.

But....... you'll never guess........!! I just looked in my old basic router cutter sets and picked out the bearing follower and nicked a smaller bearing off one of the cove cutters and put it on the 1/2" straight cutter and the thickness of the rebate is exactly the same as the thickness of the binding I have for the Sapele ukulele. I've done a trial on scrap and it works. I shall use it with the tilting body of the Makita - vertical for the top (90 degrees) and then tilted about 6 degrees off vertical for the back.

In the meantime, I've spent several hours with a cabinet scarper and abrasive to get the Acacia as good as I can. I used Starbond CA glue wicked into the tiny gaps between the binding and the wood and rubbed them over with abrasive letting the dust mix with the CA glue. It's not perfect, but it's turned out a darn site better than I thought it would be a couple of days ago.

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I'm going to leave the hole. It'll make the instrument unique.
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Re: Concert Ukulele (Binding - and damage - Cleaned Up))

Postby NickM » 27 Apr 2021, 20:23

Looking fantastic!
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Re: Concert Ukulele (Binding - and damage - Cleaned Up))

Postby novocaine » 27 Apr 2021, 20:49

well that worked Malcolm. keep it up.
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Re: Concert Ukulele (Binding - and damage - Cleaned Up))

Postby canoemoose » 27 Apr 2021, 21:09

That looks great!

That jig looks sensibly engineered, Malcolm. Looks like a sensible, albeit bulky, solution and a good build, if you're going to be building more guitar-esqe instruments. How long until you need a separate workshop just for jigs? :P
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