How to calculate fret spacing?

[MPU]

How do I calculate fret spacing for the D fret when I’m making a 32” scale fretboard by making the 1st fret of 34” scale as the nut? Isn’t the 34” scale ”nut” the fret spacing for D#? How about the D? What’s the distance between D# (34” nut) and D? How do I calculate it?
I have a 34” scale template for my fret saw and I’d like to use it for fret slotting so only that one fret spacing is missing.

 

[rudy4444]

If your scale length is 34" then multiply the scale length by (the 12th root of 2 ), 1.059463 to calculate the distance for the next half step interval of the 12TET scale. That brings you to 36.021742 (round to whatever precision you're working with.

You then use that that new calculated "scale length" and again multiply the new "scale length" for that string by (the 12th root of 2 ), 1.059463 to calculate the distance for the next half step interval of the 12TET scale. That brings you to 38.163703 (round to whatever precision you're working with.

You would really be more precise in terminology to call what you have labeled "first fret" as the nut since that's where all the other strings are located. You're really only extending your original E string for 2 additional notes.

If you want the instrument to be 32" scale length then adjust your numbers accordingly. You can run the numbers to make it anything you want it to be.

 

[MPU]

That 34” 1st fret is for my template and it is the 32” scale length nut for A,D and G. 34”nut from my template is D# and if I understood correct my D is 51,35mm from the 34” nut. At least when I add 51,35mm to 863,6 (34”) it’s 914,95 which is 36,022”.

 

[Abner]

If you are using a 32 inch scale, the D# fret would be at 33.9028 inches, and the D fret would be at 35.9188 inches. Exactly what Rudy posted above, but you want to start with a 32 inch scale rather than 34 inch.

If you want the D# fret to be at 34 inches, the D fret would be at 36.0217 inches, and the nut for the remaining strings (actual scale length) would be at 32.0917 inches.

Not much difference between them, but it may be enough.

 

[MPU]

If I use my 34” fret slotting jig template I need to measure only the nut. If I want 32” for A, D and G I need to measure every fret. For a difference of 0,1” in scale length? No, I’m going to use my slotting template. That way I can screw only one slot instead of all slots.

 

[Gilmourisgod]

I was wondering how this worked on the original Kubicki basses, I kind of ballparked it on the drawing in progress, not understanding how 32" scale can be extended to 36" without changing alll the fret spacings.

 

[Abner]

If I use my 34” fret slotting jig template I need to measure only the nut. If I want 32” for A, D and G I need to measure every fret. For a difference of 0,1” in scale length? No, I’m going to use my slotting template. That way I can screw only one slot instead of all slots.

So you don't want to do the math. Okay, you have a 34 inch fret scale, and I take it that you are building a neck from scratch, which will actually be medium scale (approximately 32 inches). If that's the case, use the example in my second paragraph above — use the first fret slot from the fret scale as the nut (for the A, D, and G strings), the "nut" for the extended E string (the open D note) will be another 2.0917 inches from the 34-inch mark, which will be the D# note. Still not clear?

 

[micguy]

The way to think about this is that your lowest string's "nut" location sets the scale length for the instrument - think of it a s a 36" (or whatever you land on) instrument, where you have a "capo" on the 2nd fret for the other strings - the "nuts" for those strings end up at whatever the 2nd fret location is for the scale length of the lowest string. If you want that location to be 34" from the bridge location (before compensation is done on the bridge saddles), then adjust the "36" so that fret 2 is precisely at 34".

Before you get to cutting wood, I'd buy a bunch of strings, to make sure you can get strings that work on the lowest string with the bridge and anchor positions you are planning to work with. It's a bad idea to build an instrument, and then find out if you can (or can't) get strings that fit it.

 

[MPU]

So you don't want to do the math. Okay, you have a 34 inch fret scale, and I take it that you are building a neck from scratch, which will actually be medium scale (approximately 32 inches). If that's the case, use the example in my second paragraph above — use the first fret slot from the fret scale as the nut (for the A, D, and G strings), the "nut" for the extended E string (the open D note) will be another 2.0917 inches from the 34-inch mark, which will be the D# note. Still not clear?

Well that’s what I’ve been trying to say all the time exept that there will be one more extended note. I see no sense calculating, measuring and marking all the frets when I can use an existing template and calculate, measure and mark only the new nut spacing if I accept 0,1” difference in 32” scale length. And that’s fine with me. As for string length, the E string playing length is a bit over two inches longer than on 34” scale bass. Ernie Ball Extra Long Scale strings have taper at 38,5” so they should work, SIT Extra Long strings have taper at 39”. For sure I’m making a test bed for checking out the string length before cutting wood.
I put my numbers in Stewmac Fret Calculator and they match so problem solved.