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View Full Version : A question about frets, fretting, neck backbow



Chris_H
09-11-2013, 05:46 AM
I have been using fretwire from StewMac, as well as their circular saw blade for cutting fret slots. I use an arbor press for setting the frets. After fretting a board, it takes an arc shape, from the compression added from the fret tangs. Seems normal. I did one in Snakewood, which is quite a bit harder than ebony, and as expected, the arc was more severe. As I glue the fretboards to the neck after they are fretted, I have not seen a problem with neck backbow. Maybe just a little issue with the fretboard 'diving' where the neck ends. I have been putting in a stiffer upper transverse brace to counter this.

No real problems... that I am aware of...

I am now about to build a couple electric guitars, and a bass, some people fret after the finger board is installed with these. With the increased number of frets, that could cause a problem. I have researched on the net, and see that other people have experienced issues with this. Some have mentioned that the Stew Mac blade might be too thin for the Stew Mac (Duncan) fretwire.

Any thoughts on this?

hawaii 50
09-11-2013, 06:20 AM
I just read a thread where the slots were cut to thin for the frets causing the neck to bow...and the uke to buzz...
and learned about neck relief on the same thread....

try searching "neck relief" on the UU and maybe It will help you understand...

Moore Bettah Ukuleles
09-11-2013, 06:25 AM
I just read a thread where the slots were cut to thin for the frets causing the neck to bow...and the uke to buzz...
and learned about neck relief on the same thread....

try searching "neck relief" on the UU and maybe It will help you understand...

I think that thread you are referring to is bogus. I've never had a neck distort because the fret board had a little bow in it before it was glued to the neck.
How thick are you fret boards anyway? They should be somewhat flexible unless they are overly thick.
BTW! If you bind the fret board it will remain straight after fretting.

Chris_H
09-11-2013, 06:58 AM
I think neck relief is a different issue. That would be a Band-Aid ( for a broken bone) to engineer that in to deal with a back bowed neck. I was under the impression that neck relief is so the shape of the top of the frets more closely matches the shape of an oscillating string, which on an uke seems more theoretical (in actuality, and relief really required) than on a longer scaled instrument. On a longer scaled instrument and chasing low action, I can see how relief can be important(but still subtle). I do not fully understand all of this yet. On ukes, I have not seen a backbowed neck. I am concerned that if fretting a longer neck with the board in place, that it may bow.

I am looking at that snakewood fingerboard now, it is less than 1/4" thick at the crown (significantly) (it is also radiused) Without calipers, I am guessing 4mm at the crown, maybe 4.5? It is bound, and it definitely did not remain flat after fretting. I like bound fretboards, have done a few. Compression from frets did leave them so they were not flat after fretting. The Ebony boards I have built required little pressure to flatten out so not an issue, more of an issue of just making sure that the upper brace was stiff enough, and not worrying if it dives slightly there. I have only been playing for less than a year now, and am not yet shredding beyond the 12th fret. Maybe next week though... :)

Words that I found on the net that most concerned me are that perhaps the StewMac saw blade is designed a little thin for their wire? Doesn't seem like that could be, as it would be too easy to fix.

Currently I have had no issues, other than I noticed that the Snakewood board definitely took a little more pressure to flatten out, but I have not built a long guitar neck yet.. Trying to avoid problems before they happen.

Maybe people were having problems from improper clamping and/or, using water based glue?

ksquine
09-11-2013, 07:27 AM
Its no problem on guitar fretboards. I get some bow when the frets are in but not more than a ukulele. There are more frets but they're farther apart and the board is a bit thicker. I haven't measured it, but it only takes a few pounds of pressure to flatten it out...a one finger amount of pressure.

mzuch
09-11-2013, 07:29 AM
I am concerned that if fretting a longer neck with the board in place, that it may bow.

Isn't that what truss rods are for? To adjust for any change in neck angle, mainly due to string tension but it could also address any relatively minor pressures exerted by a bowed fretboard.

Moore Bettah Ukuleles
09-11-2013, 07:30 AM
Maybe your snakewood fret board is too thick too flatten out. Personally, I think any fretboard approaching 1/4" is far too thick. I aim for somewhere between 3.5 and 4mm. My #764 wire goes in easily but snugly when slotted with the StewMac blade. I wouldn't want the kerf any wider. The caul I use when gluing the fret board to the neck also has matching relief.

Moore Bettah Ukuleles
09-11-2013, 07:32 AM
Isn't that what truss rods are for? To adjust for any change in neck angle, mainly due to string tension but it could also address any relatively minor pressures exerted by a bowed fretboard.

Good point. I don't use adjustable truss rods (most ukulele builders don't) but I do use a carbon fiber reinforcement rod laid into the neck. Once that is set in the neck's not going anywhere.

Chris_H
09-11-2013, 07:55 AM
I use CF in my uke necks, a 1/2" x 1/8" piece laid flat

Out of curiousity, how much relief for a tenor uke neck? I have been shown to just take a few careful passes with a sanding block on the fretboard before fretting, a difficult to measure amount.

Thank you for the info!

4.6mm is pretty far off 1/4", but still, yeah, I guess too thick

Moore Bettah Ukuleles
09-11-2013, 08:22 AM
I use CF in my uke necks, a 1/2" x 1/8" piece laid flat

Out of curiousity, how much relief for a tenor uke neck? I have been shown to just take a few careful passes with a sanding block on the fretboard before fretting, a difficult to measure amount.

Thank you for the info!

4.6mm is pretty far off 1/4", but still, yeah, I guess too thick

I don't think 1/2" X 1/8", especially when laid flat, is the best choice.
I set my neck relief at about 5 or 6 thousandths. A dollar bill, folded in half, will give you a place to start. I use one of those Al Carruth scrapers for a cleaner, flatter cut than sandpaper can give you.
Sound and playability are the single most important factors to me when I build. I take my time during fretting and set up and don't take short cuts. Regardless of how it looks or how much it costs or how much it weighs or how long it will last, an uke is worthless in my opinion if it's not a joy to play.

hawaii 50
09-11-2013, 08:31 AM
I don't think 1/2" X 1/8", especially when laid flat, is the best choice.
I set my neck relief at about 5 or 6 thousandths. A dollar bill, folded in half, will give you a place to start. I use one of those Al Carruth scrapers for a cleaner, flatter cut than sandpaper can give you.
Sound and playability are the single most important factors to me when I build. I take my time during fretting and set up and don't take short cuts. Regardless of how it looks or how much it costs or how much it weighs or how long it will last, an uke is worthless in my opinion if it's not a joy to play.

I love playing my Beautiful Moore Bettah...Thanks Chuck!

the fretwork is the best I have seen...you can tell Chuck puts a lot of time and effort into it....
now when I get a nice ukulele in my hands,I look down the neck to see if there is any neck relief built into it...

not to many builders do it...but seems to be an important part of the ukulele build...IMO

my 2 cents

Moore Bettah Ukuleles
09-11-2013, 08:39 AM
Keep in mind that most ukes built with no truss rod or reinforcement rod will develop some relief naturally after a while due to the string tension. The down side to that is that you can't control it.

resoman
09-11-2013, 09:01 AM
Chris, I'm using the same saw blade but I tap my frets in. I think I have more control that way and can actually set them more even. I'm using the same StewMac #764 wire but I thin my fretboards to 0.157 and have not had any problems. I use the CF rod too but 3/8x1/8 edge wise instead of flat. I haven't been putting relief in the FB but I will give it a go on my next. I have a baritone order so with the longer neck it might be necessary.

Moore Bettah Ukuleles
09-11-2013, 09:14 AM
I haven't been putting relief in the FB but I will give it a go on my next.

Approach neck relief conservatively. It's not a case where more is better. Too much relief will cause the strings to buzz higher up on the finger board. A matter of a couple of thou either way can make a difference.

Chris_H
09-11-2013, 09:18 AM
hmmmm.. I started out putting in 3/8" x 1/8" vertically, but switched up to the larger size based on some words that Rick wrote.. another case of different ways.. I am not sold on it by any means, though I am sure it still adds a lot of stiffness. I guess maybe I should do some flex testing, maybe break a neck or two... simple enough to measure deflection of an unbraced neck, and the 2 different orientations, deflection under a given weight, and the type of failure, and when. Of course this still would not pass 'scientific' muster....

I am not a trained structural engineer, and have not searched out the equations to find out about how different amounts/ positions of CF affect neck stiffness.

Anyone?

Chris_H
09-11-2013, 09:31 AM
Chris, I'm using the same saw blade but I tap my frets in. I think I have more control that way and can actually set them more even. I'm using the same StewMac #764 wire but I thin my fretboards to 0.157 and have not had any problems. I use the CF rod too but 3/8x1/8 edge wise instead of flat. I haven't been putting relief in the FB but I will give it a go on my next. I have a baritone order so with the longer neck it might be necessary.

I am curious about why an arbor press would set frets unevenly. I pounded them in at Pete's place, so I have felt what it feels like to set them with a hammer. With the press, they go in smoothly, never an issue. At full depth, I use the arbor kind of as a hammer, if you can imagine that, to set them fully .

My radiused fretboards are 0.150" at the side. I did not want to go thinner, as then the binding looks too miniature.. maybe a reason to rethink the radius? I like the radius though... The crown of the board in front of me is 0.183" so about 25 thou thicker than yours. Good to know I can go thinner. Thank you.

Moore Bettah Ukuleles
09-11-2013, 09:36 AM
I am curious about why an arbor press would set frets unevenly. I pounded them in at Pete's place, so I have felt what it feels like to set them with a hammer. With the press, they go in smoothly, never an issue. At full depth, I use the arbor kind of as a hammer, if you can imagine that, to set them fully .

My radiused fretboards are 0.150" at the side. I did not want to go thinner, as then the binding looks to miniature.. maybe a reason to rethink the radius? I like the radius though... The crown of the board in front of me is 0.183" so about 25 thou thicker than yours. Good to know I can go thinner. Thank you.

Look at some of the earlier ukes. Those fret boards were less than 1/8" thick. I've also heard that a thick fret board can dampen the sound, especially if it's ebony. Besides, thick fret boards just look bulky.

Moore Bettah Ukuleles
09-11-2013, 09:38 AM
hmmmm.. I started out putting in 3/8" x 1/8" vertically, but switched up to the larger size based on some words that Rick wrote.. another case of different ways.. I am not sold on it by any means, though I am sure it still adds a lot of stiffness. I guess maybe I should do some flex testing, maybe break a neck or two... simple enough to measure deflection of an unbraced neck, and the 2 different orientations, deflection under a given weight, and the type of failure, and when. Of course this still would not pass 'scientific' muster....

I am not a trained structural engineer, and have not searched out the equations to find out about how different amounts/ positions of CF affect neck stiffness.

Anyone?



Whether it's sound board bracing or floor joists, any beam will be much, much stronger if laid on edge. I use 1/4" X 3/8" rod, laid on edge. For you mathematical types (which I'm not), the strength of a beam goes up with the square of the depth of the member. So if I'm not mistaken a 1/8' X 1/2" beam will be 8 times stiffer on it's edge than if laid flat. One of you high-dome people here will correct me if I'm wrong.

Dan Uke
09-11-2013, 09:48 AM
Words that I found on the net that most concerned me are that perhaps the StewMac saw blade is designed a little thin for their wire? Doesn't seem like that could be, as it would be too easy to fix.

That was the case with my uke as the barbs were larger than the saw used. Sent it back and he had to refret the uke and add neck relief. Lesson learned and he will now put in neck relief for all his ukes.

I recall seeing a recommended Stewmac saw but it's not listed anymore...I guess someone complained that it didn't fit correctly. HAHAHA

Of course your saw could be larger. :)

Moore Bettah Ukuleles
09-11-2013, 10:11 AM
That was the case with my uke as the barbs were larger than the saw used. Sent it back and he had to refret the uke and add neck relief. Lesson learned and he will now put in neck relief for all his ukes.

I recall seeing a recommended Stewmac saw but it's not listed anymore...I guess someone complained that it didn't fit correctly. HAHAHA

Of course your saw could be larger. :)

You are getting bad information Daniel. The barbs of the fret tang need to be wider than the fret slots otherwise they wouldn't hold. That's what the barbs are there for. The StewMac slotting blades when used with the StewMac fret wire work for thousands of luthiers.

resoman
09-11-2013, 10:24 AM
I just never could get a feel for it with the press. Also, the wire would want to roll and not go in straight. It is a home made steel caul I milled a radius in and set up to float. I'm a lot faster with the hammer too.
I made a few soprano fretboards down to 1/8" but like the 5/32 better.

Dan Uke
09-11-2013, 10:26 AM
You are getting bad information Daniel. The barbs of the fret tang need to be wider than the fret slots otherwise they wouldn't hold. That's what the barbs are there for. The StewMac slotting blades when used with the StewMac fret wire work for thousands of luthiers.

You right, I probably got the right information but didnt hear it correctly and tried to pass it along incorrectly. That happens often.

Moore Bettah Ukuleles
09-11-2013, 10:28 AM
I just never could get a feel for it with the press. Also, the wire would want to roll and not go in straight. It is a home made steel caul I milled a radius in and set up to float. I'm a lot faster with the hammer too.
I made a few soprano fretboards down to 1/8" but like the 5/32 better.

How did you mill the radius in your caul? The StewMac fretting cauls are too big for the smaller wires and also need to be modified. The #764 can be hard to work with because it's so small. Some builders will use a hammer and tap one end of the wire into the slot before further pressing it in with the caul.

Chris_H
09-11-2013, 10:59 AM
I have not noticed any issues. The wire seats in the slot, and the caul presses it in. It is a 2 ton press. The wire goes in without fuss every time, doesn't bind or tip over. I had also not noticed any damage to the fret surface from the caul, though the radius of the caul is bigger. Without care, the press could cut the board in 2 pieces, I think, I do not recall off hand which wire I am using for my ukes, but is the one that people on this forum mention over and over.

Moore Bettah Ukuleles
09-11-2013, 11:06 AM
I have not noticed any issues. The wire seats in the slot, and the caul presses it in. It is a 2 ton press. The wire goes in without fuss every time, doesn't bind or tip over. I had also not noticed any damage to the fret surface from the caul, though the radius of the caul is bigger. Without care, the press could cut the board in 2 pieces, I think, I do not recall off hand which wire I am using for my ukes, but is the one that people on this forum mention over and over.

The two sizes that are mentioned here most frequently are #174 and #764. Regardless, both have the same tang width. Is there a stop on that 2 ton press? Otherwise I would be careful with crushing the wood and setting the frets at an inconsistent level.

Chris_H
09-11-2013, 11:46 AM
I am careful, and as I mentioned, to do the final set I kind of hammer them home with the press. It seems like it works well. The frets are fully seated, and I am not hearing or feeling any wood crush. I have crushed some wood on purpose.

resoman
09-11-2013, 11:52 AM
Chuck, I have a Bridgeport mill and did it in that with a radius end mill. I made a tang that attached to the caul. I was actually doing it in my drill press. I have a couple old arbor presses but wanted to try it out before I went on with the rest of the tooling and found I didn't like doing it with a press so end of that experiment.

Moore Bettah Ukuleles
09-11-2013, 12:08 PM
Chuck, I have a Bridgeport mill and did it in that with a radius end mill. I made a tang that attached to the caul. I was actually doing it in my drill press. I have a couple old arbor presses but wanted to try it out before I went on with the rest of the tooling and found I didn't like doing it with a press so end of that experiment.

Nice. I'll try that. I like the radius of the StewMac caul to match the fret wire better and have used a small chain saw file in a Dremel tool to do the job. Those cauls are brass so they clog the bit. I have some ball end mills that I could try in my mill. It should do a better job.

Beau Hannam Ukuleles
09-11-2013, 01:34 PM
I sand relief into uke necks as their is not enough tension to give it via string pull.
I use a 5mm FB which will come down a bit after levelling.
I bind them all. Hand filing the nipped excess off the tag (pic)
1/4" x 5mm carbon fiber rod.
I fret after everything has been sprayed and the neck is glued to the body. Can be finish chip outs if you not careful.
I've only ever used a hammer. (Pic)
.080" wire. (Pic)

Pic is close up of selmer FB showing relief . I don't think this fingerboard looks to thick or give any loss if tone, if so classical and flamenco guitars would have heard such a thing and thinners their FB's. but they use 1/4" FB's. I like 5mm as it adds stiffness, and strength which adds to sustain.
I took all these pics yesterday for my selmer thread (see video in that thread of me fretting)
FB58624
58625
58626

Moore Bettah Ukuleles
09-11-2013, 02:38 PM
Twenty to forty pounds of string tension is enough to put relief into most ukulele necks (unless they are grossly over-built). Pick up any uke that's over 25 years old and you'll see it. The problem is that it's uncontrollable.

AndrewKuker
09-11-2013, 03:12 PM
Just was playing your uke Beau, excellent tone. Chuck is definitely correct about the effects of long term tension, especially at a tenor scale with medium or heavy gauge strings,.....of course quarter sawn, carbon rod etc should prevent it from being significant, as you guys know and do. As far as the OP's concern, it is regarding electric guitar and bass, in which case the truss rod will allow you to fine tune the curvature. Nothing to fret about huh huh, how many times can we use that corny one.

Chris_H
09-11-2013, 03:49 PM
sorry for dropping this one on the ukulele forum, yes it was about electric guitar and bass. I know there are some experienced heads around here.. Thanks all! Good to learn more about neck relief!

BlackBearUkes
09-11-2013, 04:18 PM
I would never put the frets in a fretboard before it is glued to the neck. If you have any back bow or other problems, you are going to have to pull the frets to fix it, making much more work. It is also easier to add any additional relief to the fingerboard once it is glue on and before any fret work is done. This goes for all guitars, mandos, banjos, ukes, etc.

Beau Hannam Ukuleles
09-11-2013, 04:22 PM
I think adding thickness to a fingerboard and losing the same amount from the neck wood is a good deal in regard to strength and longevity. Ebony, or any FB wood, being stiffer then mahogany or Spanish cedar. Same overall neck thickness and feel, just stronger.

Chris_H
09-11-2013, 04:35 PM
I would never put the frets in a fretboard before it is glued to the neck. If you have any back bow or other problems, you are going to have to pull the frets to fix it, making much more work. It is also easier to add any additional relief to the fingerboard once it is glue on and before any fret work is done. This goes for all guitars, mandos, banjos, ukes, etc.

That would make binding a radiused fretboard a bit more difficult, wouldn't it?

Chris_H
09-11-2013, 04:37 PM
and clamping against a strongback withy epoxy should prevent any cock-ups with gluing? And if all else fails, making a neck is pretty easy, another fingerboard too, unless it had some crazy inlay and intricate binding details.

AndrewKuker
09-11-2013, 05:23 PM
I did it the way Duane does for years with success. But my brother now frets his boards first and they are as perfect as I've seen. No point in arguing your method of skinning a cat.
Not sure what Chris is talking about after though... I'll just get back to my work.

Moore Bettah Ukuleles
09-11-2013, 05:31 PM
I did it the way Duane does for years with success. But my brother now frets his boards first and they are as perfect as I've seen.

Sure, it's really fairly simple but it's easier if you build the neck separately from the body and have a mechanical connection. When I am lining things up perfectly, the neck goes on and comes off the body several times throughout the build. With the neck temporarily attached, the bridge temporarily pinned in and the fret board clamped to the neck, you can true things up pretty well knowing that your fretted fingerboard will fit nicely. I've done it both ways. There are advantages and disadvantages to either method. I think it's all a matter of what your comfortable with.

BlackBearUkes
09-12-2013, 02:32 PM
I am building from the perspective of one who does not build with the bolt on neck, but a dovetail arrangement. My experiences may be getting to be old school but I'm not going to change now. Also, I am repairing guitars with bolt on neck problems just as much as guitars with a dovetail joint. Both can be problematic for repair and I don't see bolt on's as being a better or easier to repair.

Moore Bettah Ukuleles
09-12-2013, 03:36 PM
I am building from the perspective of one who does not build with the bolt on neck, but a dovetail arrangement. My experiences may be getting to be old school but I'm not going to change now. Also, I am repairing guitars with bolt on neck problems just as much as guitars with a dovetail joint. Both can be problematic for repair and I don't see bolt on's as being a better or easier to repair.

I'm sure you're right. I use a mechanical connection because for my method of building certain processes are easier. And finishes are better because I don't have that cranky neck/body joint to mess with. The fact that so many of us are building quality instruments using some very different techniques just points to the fact that every builder needs to find his own way. I've never seen anyone build the way I do and it would be difficult for me to change at this point as well. I don't think we're talking about right or wrong here, just differences.

Beau Hannam Ukuleles
09-12-2013, 04:32 PM
It's just that bolt ons are ... righter :)

Chuck Dubman
09-12-2013, 07:38 PM
IIRC, the truss rod adjusts relief. Neck angle is adjusted by shimming or resetting the neck.

Sven
09-13-2013, 12:04 AM
... The fact that so many of us are building quality instruments using some very different techniques just points to the fact that every builder needs to find his own way. I've never seen anyone build the way I do and it would be difficult for me to change at this point as well. I don't think we're talking about right or wrong here, just differences.
Well said Chuck. That is if you actually said it, otherwise: well written.

Mark Roberts Ukuleles
08-09-2015, 11:21 AM
I have had this discussion with several friend/builders including Charles Fox, John Greven, and Saul Koll.
They all agree on one thing...if your slot is too thin for the tang, you will get some back bow. How much depends on the tight fit and depth of slot. Unfortunately, most suppliers of fret saws make one size, yet there is a wide range of tang sizes. I realize LMI makes a slightly wider blade, but you'll be paying extra for the blade stiffeners.
John Greven's approach was to have a machinist custom grind the blade/s for his preferred fretwire/s, with the grind on the first 1/4"-3/8" of the blade, and leave the mass in the rest of the blade. This made fretting easy, and refretting easier too. No issues with the fret jobs.
This was on a high tooth number 7 1/4" blade. He's been using the same blade for 20 years without sharpening, and he build 50 guitars a year.

It's better to chose you wire based on the fret width and crown you prefer, rather than on the tang size, but reversing the preference is and option.
Food for thought.

erich@muttcrew.net
08-15-2015, 04:57 AM
Whether it's sound board bracing or floor joists, any beam will be much, much stronger if laid on edge. I use 1/4" X 3/8" rod, laid on edge. For you mathematical types (which I'm not), the strength of a beam goes up with the square of the depth of the member. So if I'm not mistaken a 1/8' X 1/2" beam will be 8 times stiffer on it's edge than if laid flat. One of you high-dome people here will correct me if I'm wrong.

Alas, Chuck, you are mistaken. To me, it's easiest to show this in in mm, not in inches, for some reason - probably because you don't need to square fractional values:

1/8 in = 3.175 mm, squared that gives you a value of just over 10.
1/2 in = 12.7 mm, squared that gives you a little over 161, so the bar is actually 16 times stronger on edge than laid flat.

Albeit, you can't really lay a 1/2 inch bar on edge into a ukulele neck, as the neck would have to be more than a half inch in thickness - not a good idea. Your 1/4 in x 3/8 in bar sounds like a better choice for the purpose. Personally I'm still using CF rods in my necks, normally 6 mm diameter, because I bought a batch of them some time back and haven't used 'em up yet.

Another thing to keep in mind is that CF can differ a lot with respect to stiffness (vs. flexibility). We did some deflection testing with 6 mm rods from two diffent makers and there was a huge difference.

dkame
08-16-2015, 11:42 AM
Just to clarify, I believe the point is to minimization neck deflection upward (string side). It is not really a strength issue since the neck/rod will likely never yield under normal situations. Deflection under identical conditions for a cantilevered beam (neck attached at the body) is inversely proportional to width x depth^3. So in the example of rotating the rod, depth increases by 4x but width is decreased by 4x. Turning the rod so it is deeper, the amount of relative deflection is decreased by 1/4 x 4^3 or 16 times. Of course that is for the rod by itself. In any case, the conclusion is that for the same size rod, you can make the neck significantly more resistant to bowing by orienting it so it is in deeper - the way that Chuck recommends.

erich@muttcrew.net
08-22-2015, 11:44 AM
Please ignore the formula and calculation used in my previous post.

The basic conclusions, I believe, are still correct


that a 1/8 x 1/2 inch bar is not the best choice
and that Chuck's idea of laying the bar in on edge rather than flat is the right way to increase stiffness



Apologies if that didn't come across.