Help!-Fret spacing question

[RalphH]

Hi all,
I would be grateful if I could get some guidance on a fret spacing issue I may (or may not) have.
During the build of my MMB-5, (Stingray style 5 sting bass) I've been checking dimensions etc for positioning the bridge.
I noticed the fret spacing on my MMB-5 neck was slightly different than another 5 string with the same scale length.
Although not out by much, what is considered the accepted tolerance for fret differences, and how much will it effect each note? The MMB-5 neck has not been dressed as yet, and all the dimensions are to the crown of the frets.

I've attached the dimensions compared to the Stew Mac calculator.

Thanks
Ralph

[wokkaboy]

Hi Ralph, that is an interesting table. The biggest difference to calculated is 0.85mm so hopefully shouldn't make too much difference when you intonate it. I assume this is 34 inch scale length. I would say your measurements are +/- 0.5mm anyway so you should be ok when intonating it. How far in the build are you ?

[RalphH]

Thanks for the input. I'm feeling a bit more comfortable now.
Build's coming along well thanks- Headstock is shaped, 6 bolt neckplate holes are drilled, and just waiting on the preamp to arrive so I can rout the battery box hole. The routing under the control plate looks a bid dodgey, (One of the mounting holes has no timber under it) so just to be absolutely sure that everything is where it should be, I'm going to completely assemble the bass and double check everything; add/remove timber where required before I disassemble and paint it.

[wokkaboy]

sounds good Ralph. You can glue a timber block under the pickguard for the screw to bite into. Just a bit of shaping needed. Pre amp is the go they sound heaps better even with stock pups. Gives heaps more volume and more sounds. Good luck. I'll check out your build diary

[Simon Barden]

I get some very slightly different values when putting the scale length in as 836.6mm (34") e.g. 12th fret should be 431.8mm, which brings the 12th fret value that bit closer. But taking the 431.5mm and doubling it gives a scale length of 863mm, which moves all the frets down slightly and closer to your measured figures. That 1st fret value still looks slightly odd. Worth measuring it again to be doubly sure?

Did you do your measurements with both necks set as flat as they could be using the truss rod? Any neck curvature is going to affect the measured distance between the frets, so for an accurate comparison, both necks need to be flat. And also note that after it's all put together, both selected string gauge and fretting pressure is also going to affect the 'in-tuneness' of a note played.

But in the end, you won't really know until you put it all together and start playing it.

[RalphH]

I get some very slightly different values when putting the scale length in as 836.6mm (34") e.g. 12th fret should be 431.8mm, which brings the 12th fret value that bit closer. But taking the 431.5mm and doubling it gives a scale length of 863mm, which moves all the frets down slightly and closer to your measured figures. That 1st fret value still looks slightly odd. Worth measuring it again to be doubly sure?

Did you do your measurements with both necks set as flat as they could be using the truss rod? Any neck curvature is going to affect the measured distance between the frets, so for an accurate comparison, both necks need to be flat. And also note that after it's all put together, both selected string gauge and fretting pressure is also going to affect the 'in-tuneness' of a note played.

But in the end, you won't really know until you put it all together and start playing it.

Thanks for the input Simon.
After carefully measuring again, It's actually only 47.25mm to the crown of the first fret. See image below.
With all the other measurements a little less than they should be, then I can only conclude the nut is in the wrong place.

The other measurements are indeed with the neck not loaded, however the neck only has about 1mm of convex curvature between frets 1 and 21 at the moment. Set-up is going to be interesting!

[Simon Barden]

First of all I'd flag it up with an email to Adam. If it's wrong on yours then it's likely that it's going to be wrong on all the other kits so he needs to get the factory to correct this.

One possible solution is to file the side of the nut back by 1mm. However this will make the nut rather thin and liable to break in the future. You could replace it with something like brass and file that back without the same risks, but it's still a bit of a compromise.

Doing some calcs, the difference in the note frequencies on the first fret will be minimal - about 2.2 cents. You might just detect it by ear, and you'd need more than a basic electronic tuner to do so (which are generally accurate to ±3 cents) - but as I've said, differing fretting pressures can probably make as much or more difference to the pitch as the slight position offset will.

I'd see what Adam says. The factory might need to look into it and change the settings on their neck fretting cutter/router and ship out some replacement necks. However they may have made a conscious decision to move the frets slightly (though it doesn't seem to be that consistent) in order to extend the 1st fretted length slightly to make up for the fact that fretting on the first fret often tends to be a bit sharp if the nut slots are on the high side. But if you've lowered them from the standard factory cut (which is always on the high side) to the bare minimum gap without buzzing, then this effect is very much the same as for all the frets.