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Fret cutting accuracy

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I have sloooowly started work on my second build.  My first build used a pre-built Carvin bolt-on neck, which was awesome, however this time around, I'd like to build the neck myself.   I have the stewmac Japanese fretting saw, and have been building a 25.5" scale MDF template.  I used a design I found on this site for a DIY fretting mitre box (which is such a neat idea... the Stewmac one is EXPENSIVE).  Anyways... as I started cutting fret slots into the template, I realized just how difficult it was to freehand cut fret slots.  I have been measuring with digital micrometer, and then using a square to create a line for my cut (.3mm pencil).  I then use the Japanese fretting saw and try to cut exactly on the line removing the lead from the surface of the template and then deepening the cut.  I realize there are quite a few areas that I could be making mistakes above, but my main question is:

How accurate do fret locations need to be for intonation?  I went back and measured the first 7 cuts or so and here's what I've got (all are interval measurements):

1st fret 1.436   (ideal 1.431)

2nd fret 1.376 (ideal 1.351)

3rd fret 1.302 (ideal 1.275)

4th fret 1.225 (ideal 1.204)

5th fret 1.17s (ideal 1.136)

6th fret 1.078 (ideal 1.072)

7th fret 1.019 (ideal 1.012)

Perhaps worse is how straight the cut is (as dictated by the square)... For instance: 3rd fret is ~1.302 at top of fret and 1.282 at bottom of fret (worst one I measured - most appear to be within 30 thousandths).


I think at this point, I'm leaning towards chucking the template, and just buying the stewmac one, as painful as that is... but wanted to check your collective expertise for thoughts on this.  

Kinda feels like an embarassing question, considering how careful I was trying to be... but I'm not afraid to be wrong, and would rather learn from it.

Thanks for the input!

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No worries, it's all part of the learning process! There are several options out there for you, it's just down to trying things and seeing what works. Here's a couple off the top of my head: 

The G&W fret slotting box is pretty much a direct replacement for the $tewMac box at a lower price, and it works very well. Shipping takes a bit if you're in the States, but it's completely worth the wait. It'll accept the majority of commercially available fret scale templates without a problem, which is really nice. 

If you're making your own jig (the upside-down razor blade trick, right?), you could just order a pre-slotted board from LMII or somewhere similar and use that to make a copy in Richlite. That could then serve as your master template and be serviceable for a long time. 

I'm sure other members will have more (and better) advice, so stay tuned! Oh, and welcome to the club :thumb:

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I really like the idea of using a pre-slotted board as the template!  Thanks!!

Knew this was the board to come to!

Anyone have thoughts on how much variance off the ideal is still "ok"?  When is it discernable (I'm assuming the value changes depending on where you're at on the fretboard). 


Thanks again!

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To be fair, you can be a way off with a fret and it be fairly unnoticeable. The issue is with the upper frets of course, since errors are exacerbated by the narrower spacing.

For perspective, think about how much you sharpen a note just through fretting it, the width of the crown, etc. and you can soon see that fretting accuracy is less of a concern. I aim for around a couple of tenths of a mm accuracy if I'm aiming by hand, which is more than enough.

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