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Obol guitar build


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1 hour ago, Prostheta said:

In all likelihood, yes. haha

How did the shrinkage work out? Have you calculated that yet?

It shrank in a very uniform manner and didn't potato chip much at all. 

I haven't measured the shrink yet, but I will take a look at that this evening by comparing it to the master.

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What's the theoretical percentage? It'd be interesting seeing how close that ties up. I'm curious as to whether shrinkage introduces distortion as well....after all, the negative in the sand doesn't shrink and I imagine the cooling metal would pull that apart.

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57 minutes ago, Prostheta said:

What's the theoretical percentage? It'd be interesting seeing how close that ties up. I'm curious as to whether shrinkage introduces distortion as well....after all, the negative in the sand doesn't shrink and I imagine the cooling metal would pull that apart.

I honestly do not know what that number is, but both the wax and the bronze experienced a percentage of shrinkage. 

I can measure the distance from the bottom flat edge of the bridge pickup cutout to the center point location of one of the bridge stud holes to get a number that will give me a good enough idea what the difference is.

I do know aluminum's shrinkage it is .0156" per inch.

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I took some measurements.

Firstly, the shell is actually measuring close to .125" thick,  it just seemed thicker to me.

1a.thumb.jpg.15d7d2fbd9ede87761dc1485bf01faf2.jpg1b.thumb.jpg.2a5a985a7f4161d9a9af6fbc0a70abca.jpg

For the two images above: measuring 1.279" compared to 1.290" = .011" difference (this is not exact)

 

2a.thumb.jpg.f67931c991fbac6c70fdf94284565a1d.jpg2b.thumb.jpg.eada72ff1f16f2cfb807f58ddb6509b9.jpg

For the two images above: measuring 2.840" compared to 2.842" = .002" difference (this is not exact)

I will take a picture of the bronze piece sitting inside the silicone tool at some point to give a visual sense of the shrinkage.

Now that I look at these images, I really should have taken the measurement of the distance between both bridge post hole locations. 

Edited by FINEFUZZ
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That doesn't seem bad at all! I wonder if the thin-ness of the piece has much to do with that. I'm fascinated about new processes that I haven't tried myself. It sounds like there shouldn't be too much of an issue with geometry altering. That can only be a good thing.

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  • 4 weeks later...
On 6/18/2018 at 2:17 PM, Prostheta said:

Good call! Lie Nielsen also have a video doing their plane bodies being made in a similar fashion.

 

That is an interesting video as well.  I have not seen the tool that is used to do the first surfacing operation prior to the flywheel surfacing before.  Foundry work is fun to watch, but there are so many elements of the process that make it very dangerous. 

I used to do pattern work on core boxes that belonged to a railroad foundry and I never envied the workers who had to do the iron casting. 

North of my house by half an hour is the Kohler headquarters where one can tour the different facilities form porcelain work to iron casting.  Seeing them construct a cast iron bathtub is something to behold.

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  • 1 month later...
  • 7 months later...
51 minutes ago, FINEFUZZ said:

and here is a shot of the back after the rough pass-

7850.jpeg

i saw this and was like "why is there a bit dowel sticking o.... oh.  genious".  that headstock is off the hook. 

have never been to port washington (that I know of) but like anywhere else in wi... I'll assume this was all fueled by brats (hehe - go pack go)!  Note to self: buy brats... lots of brats!

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