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Leafing though the latest American Lutherie there was not much of interest. But one small tidbit caught my imagination. Harry Fleishman described a method of fretting, not in the order from fret 1 to 21, but more like the nuts on a car wheel. Starting with the first and last fret, then the middle fret and so on. He stated that this method lessened the back bow of the neck, and that he could not explain why. Here is a theory of mine that may explain it (if it actually works).

Every fret will push the surface wood upwards and downwards in the fretboard, just a little bit. Doing it in order from 1 to 21, every new fret will compress the open fret slot below the fretted fret slot, just a little bit. If the fretted slot above is filled up it won't compress, and that force will instead bend the neck, just a little bit. We got a sort of wave going on, and every new fret after the first will bend the neck, and the end result is the back bow we all know.

Doing it the other way, the third fret in the middle will have two open frets slots above and below and the neck will not bow, instead both open fret slots will compress. After some fretting there will be fret slots with a neighboring filled fret making a small bow, but not as many as with the 1 to 21 method. Also, the filled in fret will be either above or below, not always below as with the 1 to 21 method. No "wave". With filled in fret slots on both sides, the forces may compress the wood a bit more with less bending of the neck.

Any thoughts about that? I know I have to try this out for real and see if the back bow actually will be smaller

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New will change the old,
turn to ashes or gold

http://www.gammelgura.se

So if fretting the “usual way” (from the first fret to the last), is it normally necessary to adjust the truss rod to counter the back bow?

I read that too. I trust Harry, so I give it a go. It's low risk.

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Jim Watts
http://jameswattsguitars.com

Ok, what happens if we line up 21 guys and get them to hammer in every fret simultaneously?

I need to sign up for some of these periodicals. But I don’t get it. The reason nuts on tires (or engine heads, etc) are tightened that way is to avoid cracking or warping metal parts and to insure a good seal. How does this help a finger board?

If I found the neck back bowing after fretting I would loosen the truss rod and string the guitar up and let it rest (at pitch or slightly above) and see if the string tension would pull the neck "flat". I think sometimes back bow is caused by the barbs in the fretwire not fully seating and holding open each slot a little bit even if the slot and fret tang are properly sized.
When pressing frets in before the board is glued to the neck it will back bow a lot, but after clamping flat it will lay flat after removing the clamps. Again, I think this is because the barbs have then been fully seated into the wood.

I had to do a quick and dirty experiment (well, it took me half a day...). I have a heap of old replaced parlor fretboards, I selected a soft walnut one and a hard ebony one with about the same size. A piece of scrap quarters sawn spruce, about 13 mm thick, acted as a replacement for a neck. The fretboards were connected to the "neck" with wide masking tapes on both the underside of the fretboard and the "neck", glued together with superglue. This made it possible to replace the fretboard on the same "neck".

The "neck" and the two flat fretboards were thicknessed, the fretboards to about 4,8 mm, with my drum sander. All three pieces were straight and had an even thickness. The fret slots were cut with a 0,6 mm thick fretsaw to a depth about 0,2 mm deeper than the fret tang. I used some leftover brass frets (now I use EVO gold) with an unusually thick tang, at the barbs 0,85 mm and the fret tang itself 0,6 mm.

I tried the walnut fretboard first. Without any frets, the "neck" had a back bow of 0,05 mm in the middle - not exactly straight. I subtracted that from all the back bow measures. For all the measures, I put two feeler gauges 1,5 mm thick (higher than the 1 mm high frets) on top of the fretboard at the ends. A straight edge was placed on top of these, and the space between the top of the fretboard and the straight edge was measured with feeler gauges in the middle of the fretboard.

I fretted the walnut fretboard the normal way 1 to 18. The back bow turned out to be 0,15 mm. Then I refretted the "wheel nut" order. I placed the barbs on each fret in between the scars from the previous fretting session, so all the barbs had undisturbed wood on both sides of the fret slot. Now I got a back bow of 0,1 mm.

With the ebony fretboard, I did it the other way around. First the "wheel nut" order and I got 0,1 mm back bow. I had to clamp the ends of the ebony fretboard when I noticed that the tape and glue was a bit loose in one end. Then I refretted the normal way and got a back bow of 0,3 mm!

This simple experiment tells me that it is something to it, the back bow will actually be smaller if the frets are placed in the "wheel nut" order. Especially if the fretboard is made of hard wood.

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

Thanks for that Roger!

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Jim Watts
http://jameswattsguitars.com

IIRC Irving Sloane recommended doing the frets in stages. Mario Proulx frets the fingerboard off the neck, then turns the board over, puts a half inch block under the middle and clamps the ends down overnight. The barbs on the tang dig in and the next day you release the clamps and your fingerboard is dead flat. Sounded a bit odd to me at first, but Mario has a degree in aerospace engineering, so I trust he knows who he's doing.

Thanks for posting your test run, Roger. I can't figure out why it would work, but it seems that it does.

I went back and rewatched John Hall's video on compression fretting. He started by installing the frets with 0.023"/0.6 mm tangs (same as in your test run) at fret positions 1, 10, 4, and then 7 into a fretboard with no frets. So, similar to Harry Fleishman's method, he was installing the frets in a distributed manner but with the intent of introducing backbow rather than preventing it. Puzzling.

John Hall's video link (demo of compression fretting starts at 14:50): https://www.youtube.com/watch?v=XfMUSIq0f-g&t=2708s

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

I have never done compression fretting, but when putting in bar-frets as thick as the fret slot is wide at 10, 7 and 4, you have filled those fret slots firmly and adjacent over-thick frets will not compress these fret slot, instead bend the neck. He called them "neutral" in the video.

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

I know that I need to put strings on at tension after fretting is done and let the neck find its shape, at least overnight and preferable a couple of days. I think the main reason for this is that the fresh mounted fret barbs will sink deeper into the wood from the tension of the strings. Maybe I can speed up the process with clamps, I will try that next time!

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

He wasn't using bar frets, they were standard frets with tangs and barbs. He was inserting them into slots 1, 10, 4, and 7 with no other frets installed so all other slots were empty. The only fret I heard him refer to as neutral was the fret in the first slot.

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

OK! My bad.

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

Sounds like flat earth luthiery to me

Some things do make a difference but are somewhat insignificant to the whole too. I've yet to have issues fretting from end to end with a double action truss in place.

Just to be clear, I wasn't trying to dispute what you found in your experiment by pointing out how John Hall did his compression fretting using a similar way of installing the frets in a distributed manner. I like how you set up your experiment, especially how you reversed the order of the methods used to install the frets between the two necks and got the same result. A pretty strong indication that the Fleishman method may actually reduce backbow. It just seems to me that there's some sort of complexity going on that's not obvious that would explain both your results and John's results.

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Actually, I should have listened to the whole video, but 52 minutes was a bit long... Next time, I will take the time. Interesting though that it was regular frets and not bar frets. Another anecdotal "proof" for this until someone does a real scientific study.

Since I don't use a truss rod, this is very important for me. With a truss rod, no big thing. Still, why not do it the best way

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

Now I have tried the "wheel" fretting scheme and using a clamp to push the barbs into the fretboard wood when done for the first time. I let the guitar be in tension for two days as before, but this time nothing happened to the string height at the 12th fret. This is the method I will use from now on.

I had to make a stick with numbers for the frets and the placement order and put numbers on all the pockets for the cut frets to get it done right. It was actually much easier to fret the last frets, the hammer had plenty of space. The last four frets on the top was fretted and clamped through the sound hole in a second pass (16, 18, 15, 17).

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

Here is a quick follow up. The last two fretting sessions were the easiest I have ever done, I did the fret crowning in about half the time and saved more of the fret height than before. Fretting "like a tire" followed by a forced bending of the neck to seat the tangs works like a charm!

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

[quote="RogerHaggstrom"]Actually, I should have listened to the whole video, but 52 minutes was a bit long... Next time, I will take the time. Interesting though that it was regular frets and not bar frets. Another anecdotal "proof" for this until someone does a real scientific study.

Since I don't use a truss rod, this is very important for me. With a truss rod, no big thing. Still, why not do it the best way [/quote


Curious as to why you don't use a truss rod? Bob

Well, you asked for it. The truss rod have many drawbacks. Mainly, it's a tone killer. It's heavy and makes the neck dive. It doesn't do its job correctly, the tone of the guitar shifts with the tension of the rod and the relief curve is not even when adjusted. The truss rod ditch makes the neck weaker, especially at the ends of the rod. A truss rod can break or give a buzz. The adjustability of the neck is seldom needed, but the sound deterioration is there all the time.

I find the carbon fiber rod much better with fewer drawbacks, but still keeping the neck straight and stable.

All of this is of course in my opinion!

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

So, let’s say you can get a neck built with ideal relief and no truss rod. What do you do when the weather changes, or the player changes string gauge or material?

No, Roger - you did. You made all these assertions with no proof at all, and then tried to blow it off as your opinion. I've been reading your questionable posts for quite some time, and frankly - I'm tired of you. You're a wanna-be masquerading as someone with clout. Go bother the guys on Mandolin Cafe, or elsewhere. I don't think we'll miss you.

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"Act your age, not your shoe size" - Prince

I'm glad we are such a tolerant group here.

You're not talking about tolerance. You're talking about lowering the standards.

_________________
"Act your age, not your shoe size" - Prince