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  #16  
Old 02-14-2019, 04:45 PM
Dino Silone Dino Silone is offline
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Quote:
Originally Posted by Rodger Knox View Post
That happens frequently if you install frets before gluing the board to the neck. Put a 1/4" thick shim under each end of the fretboard and clamp the middle down, forcing a 1/4" forward bow in the fretboard. Leave it that way overnight, and it will flatten out. Sometimes it takes a little longer, but I've never had one that didn't flatten out.
Agree. I would argue that it almost always happens if you install the frets before gluing the board to the neck. The frets are supposed to fit snugly - you may not even need to glue them in. But, if they fit snugly, and the board isnít glued down, itís going to bend towards the side the frets arenít on.

Another reason to glue the fretboard to the neck before installing frets is that you can shape the fretboard to the neck more easily.
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  #17  
Old 02-15-2019, 12:50 AM
Talldad Talldad is offline
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Quote:
Originally Posted by Rodger Knox View Post
That happens frequently if you install frets before gluing the board to the neck. Put a 1/4" thick shim under each end of the fretboard and clamp the middle down, forcing a 1/4" forward bow in the fretboard. Leave it that way overnight, and it will flatten out. Sometimes it takes a little longer, but I've never had one that didn't flatten out.
Thanks for the tip Roger. I guess itís always going to bow to some degree. This one didnít ever even under pressure so I played it safe and regretted wider slots. My bad luck I guess.
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  #18  
Old 02-15-2019, 09:25 AM
TEK TEK is offline
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Wow, I feel as if I have been scolded for suggesting to use a "digital caliper". I guess I was not clear on how you could do it with a 6 inch caliper.

You don't have to have a long caliper to measure past the 6 inch mark. Just use a good ruler along with your caliper. So if you measurement for a fret is at 225.127mm use a ruler at the nut to mark 200 mm and use the caliper to get your 25.127mm from there. Just make sure you always reference from the nut for every fret position. I just feel better knowing my mark is at 25.127 then when it is a quarter of the way between two marks on a ruler. Hope that makes sense.

Last edited by TEK; 02-15-2019 at 09:48 AM.
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  #19  
Old 02-15-2019, 12:03 PM
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Rodger Knox Rodger Knox is offline
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Quote:
Originally Posted by Dino Silone View Post
Another reason to glue the fretboard to the neck before installing frets is that you can shape the fretboard to the neck more easily.
I build some relief into the fretboard, so I like to have the frets installed with the fretboard and neck perfectly flat when they are glued together.

Quote:
Originally Posted by TEK View Post
Wow, I feel as if I have been scolded for suggesting to use a "digital caliper". I guess I was not clear on how you could do it with a 6 inch caliper.

You don't have to have a long caliper to measure past the 6 inch mark. Just use a good ruler along with your caliper. So if you measurement for a fret is at 225.127mm use a ruler at the nut to mark 200 mm and use the caliper to get your 25.127mm from there. Just make sure you always reference from the nut for every fret position. I just feel better knowing my mark is at 25.127 then when it is a quarter of the way between two marks on a ruler. Hope that makes sense.
Sorry about that if you're talking to me. Your approach is perfectly valid, but due to the necessity of making two readings, you're not really getting any better accuracy by using the digital calipers. There's a lot of ways to do this, which usually means they all work well enough. There was an article in AL a while back comparing the intonation of a guitar with frets cut using the "rule of 18" as opposed to the twelfth root of 2, and there was surprisingly little difference.
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  #20  
Old 02-15-2019, 12:23 PM
runamuck runamuck is offline
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Does anyone know how far a fret can be installed inaccurately before intonation becomes an issue?

Idle curiosity is my only reason for asking.
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  #21  
Old 02-15-2019, 12:50 PM
charles Tauber charles Tauber is offline
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Originally Posted by runamuck View Post
Does anyone know how far a fret can be installed inaccurately before intonation becomes an issue?

Idle curiosity is my only reason for asking.
I the early 1980's, I put together a formula to calculate it. By the late 1980's I realized the formula was wrong and never bothered to correct it.

It shouldn't be difficult to calculate. Set the allowable error at, say, 2 cents (2/100 semitone), each fret is 100 cents apart, distance is inversely proportional to pitch, measured from the nut, each fret location is length from saddle to previous fret - (previous fret length/twelfth root of two)]. Easy enough to manipulate those to determine what distance yields 2 cents out.

The amount one can be out and still be within the target cents is proportional to the fret spacing - it gets smaller the closer the frets are to each other. It isn't a static number.

Practically, the answer is, "As close as you can get it". As others have pointed out, there are a number of factors that go into "good" intonation: fret accuracy is just one of them. Perfectly positioned frets with poor nut and/or saddle compensation - the norm - is more likely to result in poor intonation than a fret being more than 1/2 mm out of position.
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  #22  
Old 02-15-2019, 12:57 PM
charles Tauber charles Tauber is offline
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Quote:
Originally Posted by Rodger Knox View Post
Your approach is perfectly valid, but due to the necessity of making two readings, you're not really getting any better accuracy by using the digital calipers. There's a lot of ways to do this, which usually means they all work well enough.
Agreed.

Every measurement has some error associated with it. The more measurements one makes, generally, the larger the error associated with that measurement.

For example, there is an error in zeroing the ruler at the nut position. There is an error in placing the calliper at exactly, say, 20". There is an error associated with the calliper reading, be it small. There is an error in marking where the calliper ends. The stack-up of errors probably yields a value that is no closer to the desired value than the error of using a single ruler and eye-balling the reading to about 1/4 mm.
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  #23  
Old 02-15-2019, 01:00 PM
Dino Silone Dino Silone is offline
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Quote:
Originally Posted by TEK View Post
Wow, I feel as if I have been scolded for suggesting to use a "digital caliper". I guess I was not clear on how you could do it with a 6 inch caliper.

You don't have to have a long caliper to measure past the 6 inch mark. Just use a good ruler along with your caliper. So if you measurement for a fret is at 225.127mm use a ruler at the nut to mark 200 mm and use the caliper to get your 25.127mm from there. Just make sure you always reference from the nut for every fret position. I just feel better knowing my mark is at 25.127 then when it is a quarter of the way between two marks on a ruler. Hope that makes sense.

EDIT:. I just did what I hate, which was to chime in without reading the rest of the comments, which essentially made the point I wanted to make. In the immortal words of Rosanna Rosanna-Dana, ďNevermind...Ē

Last edited by Dino Silone; 02-15-2019 at 01:40 PM.
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  #24  
Old 02-15-2019, 04:28 PM
TEK TEK is offline
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[QUOTE=Rodger Knox
Sorry about that if you're talking to me. Your approach is perfectly valid, but due to the necessity of making two readings, you're not really getting any better accuracy by using the digital calipers. There's a lot of ways to do this, which usually means they all work well enough. There was an article in AL a while back comparing the intonation of a guitar with frets cut using the "rule of 18" as opposed to the twelfth root of 2, and there was surprisingly little difference.[/QUOTE]

Not talking to you at all Rodger, I always feel you give replies that are well thought out and worth paying attention to.
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  #25  
Old 02-15-2019, 07:04 PM
runamuck runamuck is offline
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Quote:
Originally Posted by charles Tauber View Post
I the early 1980's, I put together a formula to calculate it. By the late 1980's I realized the formula was wrong and never bothered to correct it.

It shouldn't be difficult to calculate. Set the allowable error at, say, 2 cents (2/100 semitone), each fret is 100 cents apart, distance is inversely proportional to pitch, measured from the nut, each fret location is length from saddle to previous fret - (previous fret length/twelfth root of two)]. Easy enough to manipulate those to determine what distance yields 2 cents out.

The amount one can be out and still be within the target cents is proportional to the fret spacing - it gets smaller the closer the frets are to each other. It isn't a static number.

Practically, the answer is, "As close as you can get it". As others have pointed out, there are a number of factors that go into "good" intonation: fret accuracy is just one of them. Perfectly positioned frets with poor nut and/or saddle compensation - the norm - is more likely to result in poor intonation than a fret being more than 1/2 mm out of position.
Thanks for that, Charles. It escaped me until you just mentioned it that the closer the frets are to one another the greater need for accuracy.
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  #26  
Old 02-15-2019, 10:48 PM
tadol tadol is offline
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Bruce Sexauer had some really nice corian boards precision machined with a fan fret kind of layout that you can use as the basis for a very simple jig that allows for scale lengths between about 24” and 26” - if you are looking for a really accurate and easy way to slot a fingerboard, I’d contact him and see if he has any left -
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Last edited by tadol; 02-15-2019 at 11:17 PM. Reason: Wrong matl
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  #27  
Old 02-16-2019, 12:33 PM
Howard Klepper Howard Klepper is offline
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Digital calipers, as with many other devices that have digital readouts, create an illusion of accuracy by reading to more decimal places than the device is capable of resolving. Their rack and pinion mechanism introduces multiple sources of error--the slop in how the rack and pinion are cut, slop in the pinion bearing, and slop in how the rack and pinion engage. And that is all before the pinion rotation gets translated from analog to digital.

None of those issues exist with a simple vernier caliper. I can't understand those who think they are hard to read (especially if they think they can build a guitar!).

If you are locating frets by measuring and marking, you cannot get any more accurate than using a good rule (Starrett, Mitutoyo, etc.) marked in 1/100ths, a knife, and mildly magnifying glasses if you don't have perfect vision. Cheap rules are often shockingly far off.
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Last edited by Howard Klepper; 02-16-2019 at 12:40 PM.
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  #28  
Old 02-16-2019, 04:03 PM
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murrmac123 murrmac123 is offline
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Quote:
Originally Posted by Howard Klepper View Post
If you are locating frets by measuring and marking, you cannot get any more accurate than using a good rule (Starrett, Mitutoyo, etc.) marked in 1/100ths, a knife, and mildly magnifying glasses if you don't have perfect vision. .
Hi Howard.

Just FTR, yes, you can in fact get more accurate than that, and you achieve that accuracy by using a set of Johansson gauges which you wring together to give the required location of each fret, using the nut (which needs to be already installed if only as a temporary measure ) as a datum.

The Stewmac calculator tells you what the fret centers should be , and you use a scalpel to scribe the lines.

Is the (minimal) increase in accuracy worth the extra hassle ? Probably not.

Is any luthier going to lay out the money for a set of Johansson gauges ?

Definitely not.
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  #29  
Old 02-16-2019, 05:53 PM
Howard Klepper Howard Klepper is offline
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Quote:
Originally Posted by murrmac123 View Post
Hi Howard.

Just FTR, yes, you can in fact get more accurate than that, and you achieve that accuracy by using a set of Johansson gauges which you wring together to give the required location of each fret, using the nut (which needs to be already installed if only as a temporary measure ) as a datum.

The Stewmac calculator tells you what the fret centers should be , and you use a scalpel to scribe the lines.

Is the (minimal) increase in accuracy worth the extra hassle ? Probably not.

Is any luthier going to lay out the money for a set of Johansson gauges ?

Definitely not.
And here I was sure you had risen to defend the accuracy of inexpensive digital calipers!

It's not that you can't get something like gauge blocks that will show you where the location is to a greater accuracy than 1/100th of an inch. It's that by the time you line up all those blocks, mark, and use the mark to saw the slot you won't be any closer.
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  #30  
Old 02-17-2019, 06:58 AM
MC5C MC5C is offline
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I use a decent quality (several hundred dollar when it was new) 12" dial caliper. I don't use digital calipers for much, for the already mentioned precision issues. For what it's worth, if your caliper is reading 25.127mm, then it is claiming to be reading to 0.001mm, which is 4/100,000 of an inch (0.04 thousands) accuracy. Nuh-uh. Isn't happening.

I make a point mark with the tip of my caliper leg measuring from the nut to 0.001", transfer that to a line with a machinists square and a marking knife, and cut with a hand held saw. I can do this up to the 11th fret with a 12" caliper, then I start over again. As noted, frets don't really have to be all that accurate. They are cut into wood, after all, and wood just isn't particularly stable. Then they get filed on, crowned and polished. Then they go out into the real world of humidity and heat.

One of the biggest upgrades you can make if you are doing fretboards old-school is use an extremely sharp marking knife to make your marks. Old-school cabinet making and marquetry tool, a marking knife is sharpened with only one bevel, the other side is completely flat to the edge, and you reference your square with the flat side of the blade.
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