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Radius Dish - Sealed or UnSealed?
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=6348		 Page 1 of 1
Author:  crowduck [ Tue Apr 25, 2006 11:16 am ]
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I've just received a set of dishes made of what appears to be 2 layers of mdf, each 3/8" thick, 3/4" total.
I am surprised by the light weight of the dishes, thought would be heavier.

Questions:

Is it a good idea to seal the surface with a coat of shellac to prevent warping, and protect the surface.

How about adding another layer for more weight and stability?

CrowDuck
Author:  RussellR [ Tue Apr 25, 2006 11:19 am ]
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Chris I would seal them with the shellac, some people add a backer board to stop them from deflecting during clamping, Mine are 3/4" MDF and I find they don't deflect, or at least not that I can detect.
Author:  Michael McBroom [ Tue Apr 25, 2006 11:52 am ]
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Chris,

First thing I did when I received my dishes was screw them down to good quality 3/4" plywood backing plates, then I trimmed/routed off the excess. A few months ago, I ordered another dish in a new radius and let it sit around in its shipping container for a while. Its base wasn't even close to being flat anymore. But it trued up fine when I screwed it down to its back plate.

The next thing I did when I received my dishes was I used tung oil on them. Man, were they thirsty. They drank the stuff right down. Maybe Russel's idea of shellac would work better, cuz the tung oil didn't really seem to do much more than darken them.

Best,

Michael
Author:  Rod True [ Tue Apr 25, 2006 3:20 pm ]
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I think Shane uses minwax poly on his. Any wipe on poly or finish of sorts is better than nothing.

Also, MDF comes in two different densities. The cabinet guys like to use the light stuff cause... well... it's light. Costs more, so I used the regular heavy stuff.

My dishes are 1-1/2" thick, two pcs 3/4 glued together.
Author:  Shane Neifer [ Tue Apr 25, 2006 4:23 pm ]
Post subject: 
Like Rod said...almost.

Chris, you should definately do both. The ones I make, that I sell and that I use are two laminations of 3/4 inch medium density fibreboard (MDF). They are 24 inch diamtre and weigh in at about 16 pounds. I use a router to cut the circles and join two discs together before I rout out the dish on the rim sanding machine that I made. So now I have a very stable, laminated and nicely weighted dish with an accurate radius. I then apply two coats of Varathane Diamond Finish. As Michael said, the first coat is just soaked right into the MDF. But the second coat ends up nice and smooth. THey are scuff sanded with 220 grit paper.

So...add another layer AND seal them off. Then you are off to the races! Here's a pic:



And with one piece (a MUST!) sandpaper added



Shane
Author:  Colin S [ Tue Apr 25, 2006 7:38 pm ]
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Mine are made from 18mm MDF and then backed with 18mm plywood. They were then sealed with yacht varnish, (I had a tin in the shed).

One UK supplier of dishes, the only one, sells dishes moulded from solid phenolic resin. As well as individual they can be had with a 25" dish on one side and a 15" on the other.

Colin
Author:  charliewood [ Wed Apr 26, 2006 4:36 am ]
Post subject: 
Shane you make and sell radius dishes? I didnt see anything about that on your site when I preused it - I will be in touch about one or two tho.
Cheers
Charliewood
Author:  Shane Neifer [ Wed Apr 26, 2006 1:42 pm ]
Post subject: 
Sorry about that Charlie. They are on the last page of the site, the 'price' page and near the bottom as "Go-bar/Sanding Dishes"

Shane
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