Radius disc????

[Legolas]

I just bought my first Martin kit and am collecting tools, etc...to get
started building. But I have a questions....

What is a radius disc? What are they used for? Do I need one to
complete the kit?

Sorry if this has been answered before. I did a search but couldn't
quite grasp it...

Thanks!

[B. Howard]

A radius dish is a piece of something that has a concave section carved out of it at a specified radius. They can be very useful in Lutherie but are not mandatory. I manage without one. They can be used to shape braces, support plates when gluing braces, profiling rims to mate with plates and probably some other things as well.

[tippie53]

here is how you use one. I use them to establish the proper geometry for the top and back

[Legolas]

here is how you use one. I use them to establish the proper geometry for the top and back

Hi John,

That's actually the video that got me thinking about it. But is
it absolutely necessary to use one so that the top and back
fit?

Thanks!

[Legolas]

here is how you use one. I use them to establish the proper geometry for the top and back

Hi John,

That's actually the video that got me thinking about it. But is
it absolutely necessary to use one so that the top and back
fit?

Thanks!

John....I just watched that video and realized that I hadn't seen that one. I am
an idiot. Anyway, one part confuses me. So, he does the back first to true it
up; basically leveling the side with the kerfing. I believe I have that right.

When he moves on and does the top he levels the sides with the kerfing but then
goes on to explain that Martin uses an angle on the sides near the neck block. He
explains that this is critical for the neck angle later on. I get that as well. Then he
takes another radius disc and angles the portion near the neck block. Is that a
different disc from the leveling one? If so, how many of these discs will I need?

Thanks, Mark

[tippie53]

that is me actually
I use the flat side of the disk to then make that angle flat. I use a straight transverse brace , I feel they are more stable up there. If you use a arched transverse brace then you have to flatten the top a bit where the fretboard comes on the top.

[Legolas]

that is me actually
I use the flat side of the disk to then make that angle flat. I use a straight transverse brace , I feel they are more stable up there. If you use a arched transverse brace then you have to flatten the top a bit where the fretboard comes on the top.

Oh, hi John. My fault....

So, one side of the dish is perfectly flat and the other has a 15ft radius? The
process is flattening the back, then flatten the top and then flip the dish
over and radius the top?

Thanks, Mark

[tippie53]

the back of the rim is radiused to 15 the top gets a partial 28 , that creates a ramp that is 1 1/2 degree. then you flatten that upper curve to create the ramp for the fret board.

[Legolas]

the back of the rim is radiused to 15 the top gets a partial 28 , that creates a ramp that is 1 1/2 degree. then you flatten that upper curve to create the ramp for the fret board.

But do you have one 15ft radius dish and one 28ft dish? So, 2
dishes in total?

Thank you

Mark, that is correct. A 15' radius dish for the back and a 28' radius for the top.

-tommy