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Topic: Machining cast end plates |
Jim Pitman
From:
Waterbury Ctr. VT 05677 USA
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Posted 3 Dec 2007 7:56 am |
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I have a pair of Emmons D10 raw end plates that are cast. I'd like to get a start on building a body with them. I am making a pedalless guitar for doing some vintage swing style steel. One day I may even convert it to a complete pedal steel or sell it to someone looking to build/replace a P/P body so I'd like to mimic the P/P D10 dimensions.
Since these end plates are cast, they have a draft. (taper). I assume one must machine this out to make all surfaces orthagonal in hopes of fitting a square body predictably.
Do I have the basic idea right in the steps that follow?
1. Plan the body width based on the dimensions of the inletted sections that accept the body panels.
2. Establish at least one horizontal and one vertical surface that are already orthagonal. They would be used for clamping to machine the other surfaces.
3. Mill all other surface to some final dimension.
4. Trim the top edge parallel with the shelf cast into the interior surface that gets bolted to the underside of the top body panel. Trim out any webbing on this shelf too.
5. Drill and tap the leg sockets at some angle. Anybody know the angle?
6. Be careful not to scratch/gouge the outside surfaces that are exposed since they will be sanded flat and highly polished.
Do I have the order right - perhaps the body is made then the endplates machined to fit?
It sure would be easier if I had the Emmons double 10 dimensions to start with if anyone can go to the trouble of making some measurements. I assume all Emmons P/P body panels, that is the front, back, and top, are 1/2" thick maple with 1/16" formica glued on? Please verify.
Is there anyone here on the forum that has experience doing this type of machining?
I'm no machinist myself so would be happy to pay.
Jim P. |
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John Billings
From:
Ohio, USA
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Posted 3 Dec 2007 10:18 am
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| Jim, I have no idea how to answer your questions. But,,, one word of caution. I've been workin' with some old Shobud castings lately, and the problem is, if you remove too much material from the outside surfaces, you may expose some "blow holes." Hopefully, the Emmons castings were more carefully done, and used a better alloy than Shobud did. The Shobud castings have an outside "skin" that's okay, but if you try to remove a deeper scratch or dent, things can go from bad to worse real fast! Just sayin',,,,,,, |
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Paul Redmond
From:
Illinois, USA
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Posted 4 Dec 2007 3:32 am
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When I lived in NC I used to machine endplate castings for the late Charlie Ward. I don't recall the leg angle, but believe it to be 10 degrees. When cutting these castings I was careful to only 'clean up' the draft you mentioned to a nominal fractional dimension. His castings were made by Chattanooga Pattern and Foundry in Chattanooga TN at the time, out of Almag 35. If your castings are made out of a similar material from an old Emmons endplate (for a pattern), the implied cabinet dimensions would probably be very close as Almag 35 has a low shrinkage factor. If they are made out of the run-of-the-mill aluminum used on Sho-Bud castings, they will be full of gas holes (you called them bubbles) and the shrinkage will be all over the map.
Best to find someone with a p/p and actually measure the cabinet, then go from there for your dim's on the castings.
PRR |
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Jim Pitman
From:
Waterbury Ctr. VT 05677 USA
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Posted 4 Dec 2007 4:53 am
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Thankyou John and Paul.
I believe these are original Emmons endplates. My guess is they are Almag as you mention Paul.
I see no outward sign of voids like a pinhole for example so hope I can avoid any of the trouble that John mentions.
I borrowed my friend's D10 P/P Emmons so should be able to document the dimensions as you suggest.
Jim |
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Paul Redmond
From:
Illinois, USA
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Posted 4 Dec 2007 7:56 pm
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One little thing I failed to mention is an allowance for paint thickness. That's important. If you are starting off with a 'green' cabinet, you may also want to add shims to the inside contact surfaces where the metal endplate meets the wood. If you notice the cabinet shrinking a bit over time, the screws can simply be loosened and the shims removed as needed. Regular notebook paper (which is about .0035" thick) will work fine. Start with two thicknesses which will give you a total buildup of .014" or thereabouts front to rear. Some guys use masking tape, but it tends to 'squirm' over time and you lose the desired thickness of the 'shim'. The paper won't readily do that.
PRR |
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Jim Palenscar
From:
Oceanside, Calif, USA
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Posted 5 Dec 2007 7:22 am
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| I have found leg angles to be between 10 and 15 degrees. |
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