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Fret Slotting tolerance question
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Author:  Dave Livermore [ Mon Feb 25, 2013 1:04 pm ]
Post subject:  Fret Slotting tolerance question
The one part of the build I don't trust myself with is fret slotting
But recently I decided to give it a go. So I took a pre-ordered fingerboard, used it as a guide and marked out all fret locations.

Then, made little miter box and went to town.

Fret 14 is about 1.5mm off.

What should I do? Is that enough of a variance that I should trash the whole board, which is full of inlay, or is that a small enough goof up that it won't be noticed?

Thanks,

Dave
Author:  ZekeM [ Mon Feb 25, 2013 1:08 pm ]
Post subject:  Fret Slotting tolerance question
Glue in a thin strip of whatever the fb is made of (ebony, rosewood, etc) and then re slot 14 at the correct position. The fret will most likely cover up your mishap and you will have correct frets
Author:  Alain Moisan [ Mon Feb 25, 2013 1:19 pm ]
Post subject:  Re: Fret Slotting tolerance question
ZekeM wrote:
Glue in a thin strip of whatever the fb is made of (ebony, rosewood, etc) and then re slot 14 at the correct position. The fret will most likely cover up your mishap and you will have correct frets


What he said.
Author:  meddlingfool [ Mon Feb 25, 2013 1:33 pm ]
Post subject:  Re: Fret Slotting tolerance question
1.5 mm is enough to be a problem...
Author:  Michael.N. [ Mon Feb 25, 2013 1:42 pm ]
Post subject:  Re: Fret Slotting tolerance question
Way too much I'm afraid. I get worried if it's any more than 0.3 mm off. 1.5 mm off and you can't even 'doctor' the fret.
Author:  Dave Livermore [ Mon Feb 25, 2013 2:04 pm ]
Post subject:  Re: Fret Slotting tolerance question
Thanks guys!

I wasn't even thinking it could be repaired. I was thinking it was a goner and I would have to redo all the inlay.

Much appreciated suggestion.


Dave
Author:  DennisK [ Mon Feb 25, 2013 2:09 pm ]
Post subject:  Re: Fret Slotting tolerance question
Michael.N. wrote:
Way too much I'm afraid. I get worried if it's any more than 0.3 mm off. 1.5 mm off and you can't even 'doctor' the fret.

Same here. Was your pre-slotted fingerboard tapered, or still square? Using the edge of a tapered board as a guide would throw off the positions.

For marking without a pre-made guide, you need a ruler graduated to at least 0.5mm, but preferably finer. I use 1/64", which is about 0.4mm. Mark with a fine pointed tool, and take care when positioning your cutting guide that it's the exact same distance from the marks every time. Use magnifiers if you need 'em.

Definitely a worthwhile skill to develop. It's great to be able to design instruments with short or long scales, with no thought of "what's available in pre-slotted boards?", and of course fan frets pretty much have to be done by hand.
Author:  AnthonyE [ Mon Feb 25, 2013 4:00 pm ]
Post subject:  Re: Fret Slotting tolerance question
While on the fret slotting by hand topic, I have a question on methods. I really don't want to spend the extra $ on a Stew Mac or LMI fret slot miter box, seems a bit steep although they look well made. I have the saw in my cart as I don't have a saw with the right kerf size. I am always for an excuse to by more hand saws, probably my favorite wood working tool. I would love to see some good designs for shop made miter boxes designed around fret slotting. I saw one on you tube that looks nice but would need to be made in my shop with hand tools.

My question is about sawing to the line. I find it awkward sawing one a line that Im cutting away. I have always cut to one side of a line or the other. Is this good practice to cut all your kerfs on the same part of the line and just adjust your distance from the nut to the first fret after slotting for your frets? Does this question even make sense to anyone?
Author:  DennisK [ Mon Feb 25, 2013 5:11 pm ]
Post subject:  Re: Fret Slotting tolerance question
AnthonyE wrote:
Is this good practice to cut all your kerfs on the same part of the line and just adjust your distance from the nut to the first fret after slotting for your frets?

Yep, include the nut/zero fret in your marking, and saw it like any other fret, just continuing all the way through the board. It actually makes the nut-to-1st distance half a kerf width too short, but that's a good thing. Sort of a small nut compensation. Not as good as shortening the nut-to-1st distance by 1/16" or so and compensating each string individually, but still helps to cancel out the sharpening effect of stretching strings down to frets compared to open strings.

Here's how I do my marking and slotting, which works on pre-tapered boards, and fan frets.

Start by marking a line down the center of the board. This is the master reference line. Mark a line for the nut square to that. Clamp the ruler to the board, parallel to the centerline, and mark fret positions by poking with an awl or scribe. Note that with a ruler graduated to 1/64", you can mark precisely on a line, or half way between two lines, so your accuracy is really 1/128". Mark the fret positions 3 times, near the left, center, and right edges of the board, for error-checking and to get them as square as possible.

For fan frets, the outer mark sets must follow the paths of the low and high E strings, rather than being parallel to the centerline. The center marks are of course done using the fret positions for scale length 1/2 way between the low and high scales.

Then take a wood block (mine is 1x3x6", with cork glued to one face which helps it grip) and clamp it to the fingerboard at each set of marks, gently pressing the saw against the guide block and sawing until the depth looks about right. Make sure the side of the guide block that you use is perfectly square to the face, so the slots are vertical. After you're done, you can deepen any slots that need it just by freehand sawing.

Here's what the sawing looks like. I usually start from the nut end, but it looks like I went the other way this time. Doesn't matter as long as you're always on the same side of the marks, so any offset is equal for all frets and thus cancels out (one of the reasons to saw the nut in the same way as the frets)
Attachment:
FingerboardSlotting.jpg
Author:  PeterF [ Mon Feb 25, 2013 5:31 pm ]
Post subject:  Re: Fret Slotting tolerance question
Instead of using a ruler, is it accurate enough to use a printed paper template made on CAD, or is printer error significant?
Author:  Clay S. [ Mon Feb 25, 2013 6:01 pm ]
Post subject:  Re: Fret Slotting tolerance question
I think it somewhat depends on the software and the printer, but I have heard of people doing this.
One thing to keep in mind is that the measurement becomes more critical as you approach the bridge. 1/2 a mm off at the first fret is not as bad as 1/2 a mm off at the 12th fret.
Author:  Michael.N. [ Mon Feb 25, 2013 6:07 pm ]
Post subject:  Re: Fret Slotting tolerance question
If you intend to do a number of fretboards of the same scale it's worth making a 'marking rule' rather than continually using a normal ruler. Your fret marking rule can be made of a stable piece of hardwood, square in section so that it's easy to clamp to your fretboard blank. Using a known accurate rule knife mark all the positions of the frets onto this hardwood section. Make the marks all along the bottom edge. Double check and use magnification. With a very fine saw (Zona) cut a shallow slot at each knife mark, the knife mark itself should centre the saw. Clamp this marking rule to your fretboard blank. Mark each fret position by locating a knife in the fine slots of the hardwood rule and then place a little nick on your board. Once you have done that for all positions remove the marking rule. Place a knife in the first nick, push a set square up against it. Replace the knife with your saw and use the square as your guide. The kerf of the saw will throw the position of the fret out by a fraction. That is of no consequence IF you use the same procedure for each and every fret.
I now use my Bandsaw to cut fret slots but I used the above method for well over 30 boards. It's a pretty accurate way of cutting slots and it's a lot faster than marking from a ruler each and every time.
Author:  nyazzip [ Mon Feb 25, 2013 6:48 pm ]
Post subject:  Re: Fret Slotting tolerance question
Quote:
helps to cancel out the sharpening effect of stretching strings down to frets compared to open strings

this reason, and comfort, is why nut slots should be cut as deep as possible in my opinion...right on the edge of being "too far"
Author:  Rodger Knox [ Mon Feb 25, 2013 6:57 pm ]
Post subject:  Re: Fret Slotting tolerance question
Usually printer error is neglidgible, but there are other considerations. First and foremost, was it actually plotted to the correct scale? Check the scale length with a ruler.
The other consideration is the plotting media, usually paper. Guess what, paper is made from wood, and what do we all know about wood and humidity changes? Paper stretches, but usually doesn't shrink back. Order of magnitude is 1% to 3%, depending on the paper.
Incidentally, I use patterns printed from CAD for almost everything.
Author:  dzsmith [ Mon Feb 25, 2013 7:06 pm ]
Post subject:  Re: Fret Slotting tolerance question
Here's a fretboard jig I made last weekend.
I bought a couple of Zona #350 saws for $8 a pop. The kerf is 0.022".
The fretboard is taped on top of a piece of MDF. This piece is 2.75" wide to match Stewmac's radius sanding block.
(It may be a tad hard to see in the photo)
I clamp guide boards on both sides of the MDF to guide the sanding block.
The hole in the center of the miter jig lets me line up the saw slot with the scribed line I make on the FB using a sharpened ice pick.
This is my first home-made fret board. I used Mequite.
Cheap, effective, and quite slow.
Dan
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