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Aluminum bridge
http://luthiersforum.com/forum/viewtopic.php?f=10101&t=47428		 Page 1 of 1
Author:  Tai Fu [ Wed Mar 09, 2016 2:17 pm ]
Post subject:  Aluminum bridge
Sorry it's taking so long... I needed a new mill and some tooling, plus school was taking up most of my time, and work took up the rest (I wouldn't be able to do any of this without the work).

So here's the aluminum block squared up. I realize it's still oversize but I'll fix that in a bit...

Image

Image

here is the bridge compared to the aluminum block. I will then need to cut it to size.

The reason I got 3 vise on the block is because it's a bit too long, and so the piece would flex as the fly cutter passes through it, making the finish quality bad... The vise just keeps it from flexing.
Author:  Jim Watts [ Wed Mar 09, 2016 5:17 pm ]
Post subject:  Re: Aluminum bridge
Interesting, whats the purpose of it?
Author:  Tai Fu [ Wed Mar 09, 2016 5:20 pm ]
Post subject:  Re: Aluminum bridge
No purpose... just to see if I can do it.
Author:  Jim Watts [ Wed Mar 09, 2016 5:49 pm ]
Post subject:  Re: Aluminum bridge
OK, it makes sense then. Keep us posted.
Author:  dzsmith [ Wed Mar 09, 2016 7:43 pm ]
Post subject:  Re: Aluminum bridge
Glad to hear you are back in school Tai!
Best wishes,
Dan
Author:  Joe Beaver [ Wed Mar 09, 2016 8:10 pm ]
Post subject:  Re: Aluminum bridge
How would you attach it to the top? Epoxy?
Author:  Tai Fu [ Wed Mar 09, 2016 8:20 pm ]
Post subject:  Re: Aluminum bridge
I don't... I don't intend to put this bridge into service. I don't think there's any sure fire way to attach aluminum to wood at all. Maybe small bolts backed with steel bridge plates...
Author:  Joe Beaver [ Wed Mar 09, 2016 8:33 pm ]
Post subject:  Re: Aluminum bridge
I See. Just a practice project then.
Author:  Eric Reid [ Wed Mar 09, 2016 10:11 pm ]
Post subject:  Re: Aluminum bridge
Tai Fu wrote:
I don't think there's any sure fire way to attach aluminum to wood at all..


Boeing has this figured out. FPL etch is a good first step. Phosphoric acid anodizing provides a reliable bond for epoxy on aluminum, and epoxies bond well to wood. Doing this in a small shop would be difficult, and then you're left with a bridge that weighs 3 times as much as cocobolo. As a machining exercise, it's excellent (or at least, very difficult).
Author:  Bri [ Wed Mar 09, 2016 10:23 pm ]
Post subject:  Re: Aluminum bridge
Why not try something like Burtons circle cutter or parts for the really cool kerfing machine or some other jig? When I experiment with making things I like it to have purpose.
Author:  Stuart Gort [ Thu Mar 10, 2016 12:17 pm ]
Post subject:  Re: Aluminum bridge
Tai Fu wrote:
I don't... I don't intend to put this bridge into service. I don't think there's any sure fire way to attach aluminum to wood at all. Maybe small bolts backed with steel bridge plates...


Sure there is....a phosphoric or boric acid anodize followed quickly by a BMS-1011 primer (baked on) would give the bond strength, using epoxy, about 3000 psi peel strength.

Lol....any shear failure would take the wood with it.

You could also treat the aluminum with gold alodine and then bond directly to that...and, although it wouldn't be nearly as strong as the BMS primer...it would STILL be stronger than the wood....and you could do that in your shop.
Author:  DanSavage [ Thu Mar 10, 2016 2:51 pm ]
Post subject:  Re: Aluminum bridge
Hysol 0151 has a temperature range of -65° to 160°. So, the bridge could be pulled off without damaging the underlying wood.

On etched aluminum it has a sheer strength of 3000 psi, when post-cured at 180°. When cured at room temperature for the full 72 hours, the sheer strength is 1850 psi, which is still plenty strong for luthery.

Another benefit is it's optically clear.
Author:  Shaw [ Thu Mar 10, 2016 5:10 pm ]
Post subject:  Re: Aluminum bridge
Joe Beaver wrote:
How would you attach it to the top? Epoxy?

Rivets :)

Sent from my HTC Desire 626s using Tapatalk
Author:  Shaw [ Thu Mar 10, 2016 5:16 pm ]
Post subject:  Re: Aluminum bridge
As someone who likes tinkering with my Taig mini lathe experimentation like this can really come in handy in the future especially for repair jobs. It can give you the skills you need for a practical future project.

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