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I just recently obtained a fret cutting jig so I have a couple pre-slotted LMI macassar ebony fretboards in my wood closet that I’ll use before cutting any new blanks. I took one of these pre-slotted boards out this afternoon to start a new neck and trimmed off the cut-off piece north of the nut position. I haven’t previously checked the fret distances on the pre-slotted LMI boards I’ve purchased but decided to double check this one just for grins.

I was surprised to see that the distance from the end of the board to the middle of the first fret slot was 1.412 on one edge and 1.415 on the other as opposed to the theoretical nut to first fret distance of 1.426 for a 25.4 scale length. I decided to check the one other pre-slotted board I have (board no. 2) and it’s dimensions were 1.415 and 1.419 – again slightly short of the calculated distance.

I then checked the nut to 4th fret distance which is about a far as my calipers will spread and the distance was 5.226 and 5.230 on board 1 and 5.240 and 5.238 on board 2 – right on the money on board 2 and a bit short on board 1 relative to the calculated 5.240 distance.

I’ve had these boards for over a year in a wood closet that stays at a constant 40% humidity level so I’m assuming LMI cut them dead on and there has been a bit of shrinkage over the last 12 to 14 months. I’m thinking the lesson learned here is to buy unslotted blanks and let them season for a while before cutting them.

But the $14.50 question is - - are these boards still within an acceptable tolerance and are still usable?

Thanks

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Doug Mills
Chicago, Illinois

Thanks Todd. I didn’t realize the center of the zero slot was typically the starting point for the first fret interval on pre-slotted boards. The .015 to .025 shortening you reference is a general approach to nut compensation in lieu of a more accurate compensation of individual string lengths at the nut?

Do you normally compensate your nuts? (that just sounds wrong doesn’t it) I know very little about nut compensation so just pulled up a few articles. I can’t say I’ve commonly seen many guitars on this forum or elsewhere with the nut shelves and bump outs shown for proper individual string compensation.

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Doug Mills
Chicago, Illinois

For a while (2 years maybe?) the LMI system was out of square, that might account for the issue. Put a trysquare on the reference jointed edge (the one on the left I think) and check how it sits over the frets. I recall I had to plane off even more than 1mm to make it right on the 5 or so I bought from them. Other than this, the location of the fret slots seemed fine and I didn't receive any complains about intonation.

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Build log

Alexandru,

It seems the right side of my boards (first fret on top when held vertical) is the most square with the fret slots. Sliding a try square down the edge and checking each slot shows a surprising amount of variance - many slots are right on the money and then a slot will vary from square by 12 to 15 thou (including the zero slot on both of my boards). I'll square up the zero slot and assume the other variances will not be audible.

thanks

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Doug Mills
Chicago, Illinois

If I recall well, only one side was jointed, the other left rough. After fixing the jointed edge (I think the 1mm+ loss was at the 19th fret - I was worried I won't have enough width left, classicals are wide) all the slots were right on the money. I never noticed out of parallel slots. Anyway, I guess best is to try to find an average for the squareness when rejointing, or simply return them....

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Build log

lol...
In hind sight - you could have left the 19th fret width alone and fixed up the issue at the #1 fret end... They tend to run a bit narrower up on that end

Back to the OP's question - yes, it will be off by 1/2 the fret slot width or so... because the slot is cut on center...

Have Andy cut the slots in your boards and they'll be right on!

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Formerly known as Adaboy.......