Im trying to figure out how to use a two rail sweep to make a compound radius fingerboard, or a straight radius even, anyone know how to do it?
Im trying to figure out how to use a two rail sweep to make a compound radius fingerboard, or a straight radius even, anyone know how to do it?
Post a pic of the fingerboard shape(s) in question.
-B
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To model the finger board, in either a constant or compound radius, I would do this...
- draw the edges of the fingerboard. dont connect the ends together, just draw the tapered edges from the nut to the tail end.
- draw an arc of the desired radius at the nut, going from the ends of the sides you drew and the desired height/radius.
- choose the two sides as your rails, with the arrows pointing from the nut to the opposite end.
- select the arc you drew as the object to sweep.
for a compound radius board, do NOT select the "scale cross sections with width" - which will flatten the radius as the board tapers wider down the length from the nut to tail end.
for a constant radius board, I would sweep along two parallel lines drawn from the widest part of the board, with an arc drawn at that end, and then trim to the actual tapered edges of the board. That will give you a true constant radius all the way down the board even with the taper.
The only thing you will also notice, is that with the compound radius board, the thickness at the edge of the board will remain uniform as you go from nut to body end.
With the constant radius board, the thickness at the edge will decrease from the nut as you go along the board to the body end, but the thickness at the center down the length will of course stay the same thickness.
You prob already knew that... it only comes into play if youre binding the edges.
Ok, I got it......before I read this I figured it out BUT........I thought it was the opposite as you explain as far as the thickness? I may be wrong but if your doing a compound radius of lets say....7-12.................the farther you go the flatter you get which means the nut part is actually thicker on the binding sides than the last fret is.
I think the straight radius stays the same on the side.
Now to the next question. How do I fret it along the same radius line?
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I think you need to look at the fretwire you are going to use. if it has a curved face but a flat insert- then you just want to mill a flat bottomed slot through the fretboard. If it is a curved material with a curved bottom that is an offset radius from the actual fret, then you COULD use a curved slot that mimic's the fretboard's face. But that is a lot of work to figure that out and to tool path it- and preserve safe Z that will correctly mill an arched slot and not nick the board.... ( and will take a FINE little bit, too, so it is going to be slow speeds!)
If you consider a standard saw's path- ( to create fret slots).... and if you had sanded the fretboard down and needed to deepen the slot- it would HAVE to be a flat bottom slot. I don't now or a way to align closely enough to allow the slot to be reworked with an arch to it... so I am guessing that the fretwire will be a standard roll item that you would install into a flat bottomed slot, and you would either pre-arch it or it will take the shape of the fretboard. ... (I have not built a banjo- nor installed frets- so I am responding from my knowledge of instruments and without he benefit of the latest manufacturing trends.... so YMMV.)