Radius sanding bar vs radius disc

[jjadamson]

This is my first build and I'm in the process of making moulds, jigs etc. In the Bill Cory book, Building Martin Guitars, he uses a radius sanding bar which is also used as a caul. Will it do the same job as a radius disc which will be heaps harder to make?

[Dave Sayers]

a radius sanding disc would be better but more expensive. The bar works ok. At the moment I am using a huge pine tree in the garden to anchor my router to radius wood. I shall be attaching it to beams of wood and then using it in a backwards and forward motion. The problem is holding the timber square to it as it cuts.....It's only cutting stuff on the outside of a circle, that's a radius. Think circle and how can I cut it.

[tippie53]

The bar can work but it does have it issues. Take your time and as you build more you will see the advantage to one jig over another. I used a bar but after about 10 builds I tossed it in favor of the dish, it is hard to mess things up using one of these.

[johnnparchem]

a radius sanding disc would be better but more expensive. The bar works ok. At the moment I am using a huge pine tree in the garden to anchor my router to radius wood. I shall be attaching it to beams of wood and then using it in a backwards and forward motion. The problem is holding the timber square to it as it cuts.....It's only cutting stuff on the outside of a circle, that's a radius. Think circle and how can I cut it.

Huh? What are you doing with a pine tree? Pictures perhaps?

[tippie53]

check out ( long compass ) you can do them better that way.

[jjadamson]

Hi John, I'm a little unclear about your last comment you made about the long compass.

[tippie53]

this is a method of making an arc very accurately , I think it was used a great deal in ship building.

Hi John, I'm a little unclear about your last comment you made about the long compass.

http://gicl.cs.drexel.edu/people/sevy/luthierie/compass/Long_compass.html

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