Australian/New Zealand Luthiers Forum

My CNC (desk top) has maximum X cutting area of just on 500mm, is that big enough for a radius dish? What is the standard size of the dish if there is one? Sandpaper disks seem to be around 24 to 25"s, Cheers Paul.

Hi Paul,

It is easier to sand with a generously dimensioned dish.

You could do it in two halves, or use this method which for me yielded good results for radii of 5000 mm and greater, but gets difficult for radii of less than 4000 mm, although I have made a small dish with a 2000 mm radius (200 mm wide and 2.5 mm deep) which did not turn out perfect but still good enough to use.

Hi Paul,

By my calculations, I think you would need about 530mm (diameter) of "active" (ie dished) radius dish to sand dreadnought sides (about 500mm dia for a OO body size) to get the angle on the sides and kerfing for a "normal" domed back/sides joint.

Thanks,
GregL.

We did a compound radius dish on our CNC just for ukuleles...10 ft rad across and 5 ft rad lengthways I found a rectangle shape works great...It dosn't have to be a circle.

timbuck wrote:We did a compound radius dish on our CNC just for ukuleles...10 ft rad across and 5 ft rad lengthways I found a rectangle shape works great...It dosn't have to be a circle.

Hmmm! I can do that in Vectric using a 2 rail sweep, it's how I do my compound radius fret boards, cheers Paul.