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Apparently my skills are in need of refinement. I made a plexiglas template yesterday for a 28" baritone that I laid out straight off my Stewmac straightedge with an exacto, always measuring from the datum, as laid out by the Stewmac fret calculator. I can't think of how I could be more precise, by hand, anyway. I do know that the cheap, thin-kerf tablesaw blade I used to make the cuts could've introduced some runout, but the resulting discrepancy in the ebony board I slotted seems greater than this. I'm now wondering if the fret calculator accommodates for fret slot thickness in it's determination of the first fret position. In other words, should I offset half the thickness of a fret slot at the nut, or is it incorporated into the calculations? Surely it must be, right?

I'm going to give it another shot today, before I start shopping for a local laser-cutting service. I'm going to add stiffeners to my saw blade. Any other suggestions?

Ken

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Mountain Song Guitars www.mountainsongguitars.com

All of those measurements are for the point that contacts the string. So 0 is the very front edge of the nut (i.e. the ver beginning of the fingerboard) and 14 should be the very center of the fret slot. It looks like you're off by quite a bit.

First of all, don't ever trust the very edge of a ruler...especially a wooden ruler. They get worn out and are seldom accurate. Measure starting at 1", and add an inch to all of your measurements.

If you're making a .023 slot, when you cut the nut it should be offset by half that to account for the thickness of the blade. If you move the ruler back about to that point, that accounts for a good bit of the error you're seeing at the 12th.

What does you template look like? What do the other locations look like?

Ok, so you're saying that the values of the fret calculator don't reflect that offset. Wait, you're right, of course they don't, hence the 14.000 value listed for the 12th fret! What a dumb@$$!Why didn't I put that together before cutting my template...

I guess the good news is that I should be able to modify my template (plexi) without making a whole new one.

Sometimes the obvious needs to be pointed out to us... Thanks, John.

Ken

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Mountain Song Guitars www.mountainsongguitars.com

Yeah, it's as though the nut is a 0 fret. Everything reflects the center of the fret, so the nut is off if you just go to the center. It looks like you're off by more than .011, though. There's another source of error somewhere, but the .011 gets you a lot closer.

Yeah, checking the other slots, there's just too much variance. I don't think I can get my tolerances tight enough for my liking by hand. Fortunately, I found a guy locally who's cutting one for me on their laser cutter. Fairly easy to draw out in Rhino, so I went ahead and drew out spacing for my parlor on the other side.

Ken

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Mountain Song Guitars www.mountainsongguitars.com

None of the readily available fretting template or slotting services allow for the width of the saw blade at the nut.
However, that half kerf width provides some nut compensation which is useful so in practice there is no problem.

My StewMac one I have appears to have the .011" offset at the nut when I measure it, but it's not easy to measure so maybe I'm off a bit. Maybe I'll send them an e-mail and ask out of curiosity.

Ok, so delving deeper into the nut compensation issue, it appears that, based on the discussion in this thread:
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=22539&hilit=nut+to+first+fret+error
That the nut slot of the template actually needs to be compensated around .024" towards the bridge from theoretical absolute zero. So, if my thinking is on track, since the original slot already adds half a fret slot's comp, I still need to shorten the nut-to-first fret distance by an additional .012". On the drawing I did in Rhino, I actually moved the nut slot .012" away from the bridge, so the nut hits the theoretical zero point. So, to correct my drawing, I'll move the slot towards the bridge the full .024". Clear as mud, right?

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Mountain Song Guitars www.mountainsongguitars.com

Sounds good. I'm planning on a fully compensated nut on my current build. Been into my Contemporary Acoustic Design.

I first did fretboards by measuring with a ruler, by hand. I have a 36" machinists ruler that is marked in 100ths of an inch and I was concerned that may not be good enough (it is). I found pretty quick that although you need to do a good job, you don't really need CNC laser precision. Great if it's convenient just not crucial to the task so don't drive yourself nuts over this.

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Steve Smith
"Music is what feelings sound like"

That's good to know, Steve. I did luck out, though. I found a sign shop down the road that cut me a template on their laser cutter, from a dxf file I exported from Rhino. It looks fantastic, but I'm going to put it under the lens and check it for accuracy before pressing it into use. In fact, if it works out, I may offer to make custom templates for purchase, at a very reasonable price, of course. Here's a quick phone pic:

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Mountain Song Guitars www.mountainsongguitars.com

That looks good - hard to beat if you can get it done at a reasonable cost. I have to admit that I use CNC-cut templates from several sources with a sled and a fretting saw blade on the table saw to do my fret boards now.

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Steve Smith
"Music is what feelings sound like"

Ken,

Please let me know if you decide to sell the templates, I'd like to have one of the 24.375" templates for my parlor builds.... Thanks!

--Jay

Will do!

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Mountain Song Guitars www.mountainsongguitars.com