Fret slot sawing accuracy
 

I’ve never slotted my own fretboard before and as I embark on it for the first time, the level of access necessary seems daunting.

I like working in metric, so I calculated the scale in millimeters.
When I see measurements like 100.235mm, I wonder how I’ll ever measure that. I can see getting to 1/2 mm, but accuracy beyond that seems like it would be a swag at best.

So, the question is this: can I round to the nearest 1/2mm, or should I acknowledge my limitations and get a pre-slotted board?

Get yourself a digital caliper and life will be easy. Not that expensive (less than $20) and you will find yourself using it daily for other things. You can get ones that switch from inches to mm with the push of a button.
Travis

Typical fret wire has a 0.5mm (0.020") tang width. Rounding to 0.5mm allows a max tolerance of 1/2 tang width. OK for me; don't know about you.

I have a digital caliper, but not nearly long enough to measure fret spacing from the nut.

Yes, and you are right to measure every slot from the nut. Using calipers to go fret to fret would have huge measurement errors build up as you got closer to the soundhole.

TLDR; Don’t use a caliper. Use a trusted ruler with millimeter markings, and round to the nearest half-millimeter. Always measure from the nut, not from the last fret.

I round to the nearest half-millimeter, and just use a trusty ruler. No caliper. I’ve never seen a caliper that will stretch the length of an entire fretboard, but one may exist. If, instead, you’re using a “normal size” caliper and making relative measurements from the last fret (instead of from the nut), you have a much better chance introducing and propagating errors with your “super-accurate” caliper than you would if you just used a good ruler and measured from the nut. (Which is what you’re supposed to do...)

Unless you’re cutting with a laser beam, you cant cut your slots with better than half-millimeter precision anyway. And fret wire has a certain width. And fretting a note with different string actions, different tensions, even different pressure will change the pitch more than being off by less than a half-millimeter in slot placement.

One of the real downsides of digital everything is that it gives us the ability to measure with no more accuracy, but with the illusion created by increased precision.

All guitars, including really good guitars, were made for a very long time without worrying about stuff like this.

There are digital calipers that big, but they are not cheap, and are really not necessary. You can miss the "correct" spot by half a MM and the intonation will be less than 2 cents off due to the misplacement. That's less than the difference between equal temperament and just temperament, and most people don't notice the compromises with equal temperament.

I typically print out a paper pattern with the fret positions marked, tape that down the middle of the fretboard, and mark the fret positions. I cut the slots by hand with a Japanese fretsaw, which is a pretty primitive way to cut fretslots, and I've never had problems with accuracy.

What do you use to draw the fretboard scale in order to print it?

fret slotting
 

What about the use of the various fretting templates out there? Yes, it is a bit of an outlay of funds but the accuracy is generally spot on.

I use an engineering and drafting program called MicroStation, the printout is very precise. The largest source of error is paper stretch, paper also expands with increase in humidity. It's less than a couple of MM over the scale length, and I use the same pattern to locate the bridge. If I was concerned with the paper stretch, I'd print the pattern on polyester film which does not stretch.

Similarly I drew mine using a vector graphics program and punted it out to scale using photoshop I then glue it to the fretboard and saw carefully.

Top tip: make sure that the saw blade width is equal to the tang width, 0.5mm.

I once cut a fretboard with a 0.3mm Japanese saw, fitted the frets to find 20 x 0.2mm = 2mm worth of wedging in the board. My fretboard was no longer flat but arched.

Very first guitar I built (when I was seventeen years old) I used a metal ruler with mm markings. The guitar intonates great.
Not that hard to do. Just use the right calculations for determining fret spacing.

I don’t make a paper template - there’s really no reason to add that additional level of complexity. I use an online fret calculator (like the one at http://liutaiomottola.com) for the scale length I want, and i tape my ruler to the fretboard blank. Read off the values and make a mark. Never had a problem.

I use the calculator because all the instruments I’ve built have had different scale lengths, and none of them used a standard scale length. The fret position rules from the luthier supply places might make sense if you were building a ton of guitars. But for the home builder, they’re hard to justify - they save you all of about 15-20 minutes per instrument.

I cut the fret slots themselves with a dozuki - I think it’s basically the same saw that’s sold as a Japanese Fret Saw, only cheaper. It fits the tangs of medium/medium frets perfectly and I’d imagine others as well. (I don’t think the tangs vary much, but I could be wrong.) Again, never a problem.

When cutting the frets, I use a bench hook to brace the blank against, and use a small machinist’s square as the guide for cutting exactly square to the blank. It’s a low-tech system that reuses woodworking tools I already had, and works perfectly. And doesn’t even require any power tools, which for me is always a plus.

[QUOTE]I have a digital caliper, but not nearly long enough to measure fret spacing from the nut.[QUOTE]

I purchased one of these to check fret location accuracy when dealing with intonation issues. I borrowed a very expensive version of the same caliper from a friend and I worked so well I decided I needed my own.

0-500mm Heavy duty Digital Caliper search aliexpress less than $100.

https://i190.photobucket.com/albums/...o/IMG_2302.jpg

Fred

That happens frequently if you install frets before gluing the board to the neck. Put a 1/4" thick shim under each end of the fretboard and clamp the middle down, forcing a 1/4" forward bow in the fretboard. Leave it that way overnight, and it will flatten out. Sometimes it takes a little longer, but I've never had one that didn't flatten out.