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(absurd project) Aluminum bridge
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=46849		 Page 1 of 3
Author:  Tai Fu [ Wed Dec 16, 2015 1:33 am ]
Post subject:  (absurd project) Aluminum bridge
I got a mill, and well I'm basically looking for nails to pound.

I know this sounds silly (as its going to weight a lot and probably sound bad), but I want to make an aluminum bridge. A standard, Martin style bridge out of 6061 aluminum.

I do not have CNC, so I'm going to do this the hard way, meaning I would basically have to find a blueprint, and calculate tool path (perhaps with those MasterCAM type software to tell me how to do this?) and surface profile them with a round nose endmill. So for example I want to make the bridge top have a 16" radius I'm going to find out how I can take a cut, move the X axis by say .01", raise the cutter by however much it takes to make the right profile (I'm going to need help in doing this), make another cut, and so on. Going to be very tedious for sure. The bottom will also be profiled for a 28' radius to match the soundboard.

The other challenge will be profiling the actual shape. I could "draw" it by manipulating the handle, but how do I do this in exactly the same way every time?

I doubt I'll actually use this bridge in an actual guitar (how would you glue it?) but I want to do this as a way to hopefully improve my machining skill.

Any help would be appreciated...
Author:  Barry Daniels [ Wed Dec 16, 2015 10:12 am ]
Post subject:  Re: (absurd project) Aluminum bridge
You are trying to do something that the tool was not designed for. Mills are not controllable for a non-flat surface profile to be cut smoothly. This will be an exercise in frustration. You would be better off using a belt sander.
Author:  kencierp [ Wed Dec 16, 2015 10:35 am ]
Post subject:  Re: (absurd project) Aluminum bridge
I agree with Barry -- why not get familiar with the machines capabilities with a project of substance. Frankly if it were even possible your (absurd) project sounds like a colossal waste of time to me.

Bridge pin drill guides -- tuning machine drill guides -- fret leveling tools
Author:  kencierp [ Wed Dec 16, 2015 10:59 am ]
Post subject:  Re: (absurd project) Aluminum bridge
To my point ---- our Martin Belly bridge CNC program has more than 18000 lines of coordinated XYZ commands. Plus a separate pin hole and slot file which BTW would actually be a good mill project.
Author:  Tai Fu [ Wed Dec 16, 2015 12:10 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
So how did they make complex shape before CNC?
Author:  kencierp [ Wed Dec 16, 2015 12:23 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Quote:
So how did they make complex shape before CNC?

Production line likely using a shaper and/or operations like this:
http://www.frets.com/FretsPages/Luthier ... blank.html
http://acousticbox.com/martin-bridge/
Author:  Tai Fu [ Wed Dec 16, 2015 12:41 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
That's fine with wood. I doubt you can do this with aluminum. So how did they make complex dies and mold out of metal before CNC?
Author:  kencierp [ Wed Dec 16, 2015 12:54 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Quote:
I doubt you can do this with aluminum. So how did they make complex dies and mold out of metal before CNC?

Actually you can do that with aluminum or even steel using the proper speeds and feed and cutters -- I think maybe you need to get a book regarding basic manufacturing and machining.
Author:  Tai Fu [ Wed Dec 16, 2015 1:05 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
If you put a piece of steel to a wood shaper very bad things will happen. RPM is too high and the hand's feedrate will be far too fast for it to be safe. In a mill the piece is clamped down because the force generated from high speed machining is going to tear the piece out of your hand before you can even react. For example try hand feeding a piece of aluminum into a spinning end mill... I wouldn't do it.
Author:  kencierp [ Wed Dec 16, 2015 1:30 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Who said anything about hand feeding? -- But anyway seems you have it all figured out -- best of luck to you with your project.
Author:  Dave Rickard [ Wed Dec 16, 2015 2:58 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
You need some training on the mill.
If it make any difference to you I spent over 40 years working in a machine shop.
Your getting good advice, I wouldn't argue with them.
Author:  David Collins [ Wed Dec 16, 2015 3:13 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
I would simply second what others have said. First, a conventional milling machine would not be an appropriate or ideal tool for this task. Second, if your goal is practice and learning of machining skills, this project would not be useful toward this goal either.

There are many more basic skills and familiarity with cutting paths, depths, speeds, bits, layout, referencing, alignment, etc, with basic shapes before trying anything so complex. Start with simple 2 dimensional plates and 90° corners, then work your way forward from there. Once you get going and see all the factors demanding practiced strategies which you probably never even thought of before, you'll have no shortage of goals to practice toward on much more basic tasks.
Author:  Andy Birko [ Wed Dec 16, 2015 4:09 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Tai Fu wrote:
So how did they make complex shape before CNC?


With difficulty!
Author:  Chris Pile [ Wed Dec 16, 2015 4:49 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Quote:
So how did they make complex shape before CNC?


There were other machines before CNC - tracer mills, shapers, die mills, etc. Truth be told.... It's planning and skills directing the proper use of machines and hand tools.

I've made acoustic bridges pretty quickly with a bandsaw, a set of files, a beltsander, and a drill press. In less time than it takes to make a mill fixture a few minutes of using your kidneys and some elbow grease will get you far. [:Y:]
Author:  Dave Rickard [ Wed Dec 16, 2015 5:17 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Take a look at a variable pitch prop.
They were made several years before NC.
Planning and skills ruled back in the day.
Author:  Tai Fu [ Wed Dec 16, 2015 6:03 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
I mean honestly I could still go ahead on the project. All I really need to do is use the end mill to hog out a rough shape (means I use a ball end mill and take fewer passes resulting in a rough finish) and then finish it off with a file like a normal wooden bridge. I made countless wooden bridges so I am familiar with how it works.
Author:  Alex Kleon [ Wed Dec 16, 2015 6:13 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Tai Fu wrote:
I mean honestly I could still go ahead on the project. All I really need to do is use the end mill to hog out a rough shape (means I use a ball end mill and take fewer passes resulting in a rough finish) and then finish it off with a file like a normal wooden bridge. I made countless wooden bridges so I am familiar with how it works.


Sounds like you've answered your own question, Tai! Take some pictures so that we can see your process, and the finished product.

Alex
Author:  Barry Daniels [ Wed Dec 16, 2015 6:32 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Yeah, but why? A lot of effort for something that will be acoustically dead.
Author:  Bob Garrish [ Wed Dec 16, 2015 8:17 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
I could make a pyramid bridge or a Martin bridge on a manual mill with a rotary table and a few roundover and chamfer cutters. It'd be a bit slow for my style, though; the whole 'zip out a bridge in three minutes on the CNC' thing really does it for me. If it was 1950 and I needed a mold master...Barry also brings up a good point about utility. It's a lot of work to put into a paperweight or a question-maker.

It's kind of like building a car in order to learn how to use a wrench in terms of complexity, though. Make some useful stuff with the mill, like drilling and routing guides, and then maybe make a radius block on the mill to see what cutting a radius point by point feels like. Everything is 100X faster if you have a DRO, and they're not priced horribly on Shars (all things considered).
Author:  Grant Goltz [ Wed Dec 16, 2015 8:37 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Tai Fu wrote:
That's fine with wood. I doubt you can do this with aluminum. So how did they make complex dies and mold out of metal before CNC?

Well, for most things they DID start with wood, be it a shampoo bottle or the fender for a car. They called those folks "pattern makers" and they carved, planed, scraped, and sanded the prototype patterns for almost everything out what was then known as "pattern makers grade mahogany", the same HOG we all wish were still available for guitar necks. From these wooden prototypes, the molds were made to produce the final product, be it in metal, glass, or plastic. All that was required was skill, training, and good eye-hand coordination, not something that everybody has.

Grant
Author:  Tai Fu [ Wed Dec 16, 2015 8:42 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
So before CNC they had "pattern maker" who basically makes wooden model of stuff? I know CNC requires skill too but it doesn't seem like it anymore (download a CAD drawing, feed it to a CAM software, almost like hitting the "print" button)
Author:  Alex Kleon [ Wed Dec 16, 2015 8:54 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Tai Fu wrote:
So before CNC they had "pattern maker" who basically makes wooden model of stuff? I know CNC requires skill too but it doesn't seem like it anymore (download a CAD drawing, feed it to a CAM software, almost like hitting the "print" button)


I think there is a bit more to CNC than downloading software and pushing a button! Some people make it seem easy because they've put a lot of study and work to get to that point.
I've learned that when someone makes something look easy, it ain't always necessarily so!

Alex
Author:  David Collins [ Wed Dec 16, 2015 9:28 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Tai Fu wrote:
So before CNC they had "pattern maker" who basically makes wooden model of stuff? I know CNC requires skill too but it doesn't seem like it anymore (download a CAD drawing, feed it to a CAM software, almost like hitting the "print" button)


Oh me, oh my. No. There's a bit more to it than that. Of course by "a bit", I mean details that could probably be covered in a few full time semesters.

I would strongly recommend starting with some much simpler projects - there is a whole universe of complexities that exist in doing good work with this tool which you haven't even imagined yet.
Author:  rlrhett [ Wed Dec 16, 2015 10:31 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Tai Fu wrote:
So before CNC they had "pattern maker" who basically makes wooden model of stuff? I know CNC requires skill too but it doesn't seem like it anymore (download a CAD drawing, feed it to a CAM software, almost like hitting the "print" button)

Wow! That is WAY off. Ask Andy Birko if he just downloaded a file and hit print to make his necks. Maybe some of these CNC toys out there for retired folks to carve their grandkids names into a flat cutting board. Otherwise, there is nothing plug and play about CNC.


Sent from my iPad using Tapatalk
Author:  Bob Garrish [ Thu Dec 17, 2015 8:16 pm ]
Post subject:  Re: (absurd project) Aluminum bridge
Andy totally does that! It just took a few thousand hours of experience to make the file is all...
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