Reverse fingerboard radius?

[Grommet]

Hi all,

After 8 months of daily use (1-2 hrs a day), the 1st 5 frets on my learner mando, an A-style Santa Rosa, were grooved deep enough to affect intonation, particularly on the A strings. The grooves were worst on 2-5 and only under the unwound strings. Assesing the job ahead, I looked at the Frets.com articles and checked this forum finding lots of good tips. I had always thought the frets looked a litle concave to my eyes, but after removing the strings and checking with a straigtedge perpendicular to the neck found that both the frets and the fingerboard had a slight but noticable negative radius. Is this common? I assumed that this was a a manufacturing defect resulting from exessive clamp pressure, cupped wood, or a poorly prepared neck surface.

Long story short my fret leveling and dressing fixed the intonation issues and made the upper fretted notes sound much better as well...but I couldn't bring myself to go with a negative radius sanding block to achieve the leveling, thus the fret ends now have less height above the board than the center of the frets. This will reduce the number of fret dressings that can be performed of course. I'm pleased with the intonation and the new smoother feel of the neck...but should I have maintained the concave radius?

Also, I used an alternative to a fret crowning file found here on the forum. Drilled a hole through a block of wood (for my frets, a 1/16 drill bit looked a good match to the fret crowns), split the block along the drill hole (ok this was a tedious process in oak using an x-acto saw) and used 400 grit sandpaper to line the hole in one block half and stroked each fret 30-40 strokes. Results were not quite as domed a profile as I would have liked to see, but after polishing th frets with 0000 steel wool, the old beater sounds better than it has in weeks. The new J74s helped too.

Scott

[billhay4]

I'd leave it like it is until the frets are done for. Then, I'd sand the fretboard level and refret it.
Bill

[Grommet]

Thanks for the input Bill. That is likely exactly what I will do if I do anything more to it down the road. If it a were a valuable instrument I would not have ignored the fingerboard (nor would I have have attempted my first repair job). Hopefully it will serve well for another 8-12 months at least. Maybe I can ease-up on the death-grip a little.

Scott

[Clement Barrera-Ng]

Scott - I agreed that the dip in the middle of the fretboard is most likely manufacturing defect, or defective wood used for the fretboard. Bill's suggestion to level the fretboard by sanding and then refret is the way to go. I also like how you fashioned your own fret file - it's ingenious. However, when you're ready to go a complete refret, I would definitely recommend getting a proper fret file for the job. Doesn't have to be a very expensive one - you can file cheaper alternatives on ebay, or the Gurian file on LMI.

[Grommet]

Barrangatan- Hopefully the board leveling and refrett of the laminated Santa Rosa will wait for a while now. For the moment I'd rather practice than experiment.... but I do have some old piano soundboard wood I'd like to massage into a pancake sometime soon. So, the Gurian or some other fret crowning file is a likely future purchase. The alternative fret crowning process using a drilled and split block with sandpaper idea came from a 2006 post by Charlie Vickers and a later poster whose name I have forgotten.

Scott

[DerTiefster]

A violin has a positive radius (convex) so the bow can access one string at a time. It is my feeble opinion that the convex mandolin fretboard makes it easier to pluck the intended strings without striking the others. That's how it feels to me when I go back and forth between flat and convex fret boards. So I'd call a concave fret setup a manufacturing defect or a sign of a character deficit, present company excepted, of course.

[Grommet]

Good Point DT,

That'll be a convienient excuse for being less strong as yet on tunes heavy on the cross-picking.

Scott