CA in the fret slot?

[Brian Burns]

Hello All,

I was watching a Stew Mac video the other day, and the fellow that was demonstrating---not Dan Earlywine---said to run some thin CA along the edges of the frets for "better tone quality".

I make classicals, and am wondering if this might apply to my builds. I'm quite fussy about getting the fret slots right at .023", and use Jescar fret wire---no problems with frets coming loose.

My first thought is that the CA would help in doing a fret job, with slots a bit too wide, but I thought that I would ask.

Cheers,

Brian

[Brian Burns]

Hello John,

That's a good question!

Unlike most classical builders I make a conical section radiused fingerboard---18 inches at the nut, and 28 inches at the 19th fret. That's not much of a radius by steel string standards, but I slot my boards before routing the radius, so the slots leave a gap below the fret in the center of the board. 

Where can I get a research grant to test this out?

By the way, players seem to like the radiused board as it makes barring easier. Often the player doesn't notice the radius until I point it out!

Cheers,

Brian

[Russell Vance]

Hi John,

While we have a default/standard fret size for everyday work the customer ultimately has the final say in choosing fret sizes and radiuses. Along with that choice comes a variation in fret tang depth and width.  We also do a number of radius checks and trues in the process of bringing a fingerboard to completion. All this happens after initial slotting on our machine saw gig which has mechanical limitations.  Consequently we cut  flat fret slot bottoms with a prudent tolerance gap.

We use unbound fingerboards to enhance performance and stability and initially inject thin CA in from both sides of the board and once that has cured we then finish the job by wicking in medium CA to seal the deal and tidy the ends.  This medium shot also has the added bonus of filleting out finishing marks in the fret end area and adding security to this critical part of the fret.  This final shot of medium CA pads out the fret bottom and fills the gap to some extent and we live with that.   Also, for attribution purposes;  I pinched this process from PRS who show it on their Youtube Vids if our readers are interested.

I would like to have a conformal fret slot bottom but the reality of making in numbers is that even that form would need a tolerance gap.   I think the extra material removed in a flat bottom slot is significant but as we have good tolerances we can compression fret to a small degree and the CA applications into the slot fills this area a bit, stiffens up the board and adds consistency anyway.

Regards,

Rusty. 

[Walter W Wright]

i've worked on plenty of very expensive guitars with fret ends that have sprung up over not even that long a time. it's not awesome when i'm cleaning up the board on a 10-year old $4000 boutique acoustic and i get nice little tufts of steel wool stuck up under the fret ends all the way down the board :(  a proper CA fret installation would have prevented this situation.

CA is great for frets because it fills gaps, doesn't introduce water to the slot to swell the wood and throw off your leveling afterwards, seals the slot from any further moisture, and dries "brittle" for nice tone transfer. 

you obviously don't want to use glue as a substitute for a proper tight slot fit, but in addition to such it's the ticket for reliability.

over on TGP famed luthier terry mcinturff turned us on to the type of CA he uses for his builds; it's called loctite gel and comes in a little bottle from the hardware store here in the US at least.

the shape of the bottle tip and thickness of the glue makes it really easy to lay a thick bead right down into the fret slot and then press the fret in with zero squeeze-out.

[Brian Burns]

Hello Walter,

TGP ? Whazzat? 

Frank, did some experiments with hot hide glue some years back, and I was surprised to learn from him that it has much better heat resistance than the poly vinyl glues (Titebond et al), and probably than CA---acrylic plastic when set up. Perhaps FF could say whether that applies to fish glue as well.That could be another reason for using CA---to make frets easier to remove. 

Cheers,

Brian

[Walter W Wright]

the gear page

a much bigger forum than this one, a bit more electric guitar-oriented, but still a wealth of really good stuff for builders and repair guys, i've learned quite a bit there over the years from masters like john suhr and terry mcinturff.

here's one relevant thread

https://www.thegearpage.net/board/index.php?threads/which-glue-for-...

(oh, and FF's oven experiments with hot hide are what showed me the way to using it for those jobs a long time ago too)

[Brian Burns]

Hello All,

I decided to check with Trevor Gore on this topic, and he very kindly responded with the following:

"Regarding gluing in frets, it depends on how good your fretting technique is.  The test I use is to take a medium sized, flat-head screw driver and drop the tip from ~ 6mm up on to each fret under each string position and listen for the “ring”.  (Wooden-handled screwdrivers, if you’re old enough to have one ;-) , give a better ring). Frets not properly seated in a location sound dull compared to other positions on the same fret or other frets. Mostly, you can’t see any difference in how the fret is seated.  If you get 100% pass mark in this test, there is no need to glue in the frets.  I reckon I have pretty good fretting technique (I press in frets and never dress them, because they are level enough not to need it). And I glue them in.  Also, in varying humidity, fretboards expand and contract in length with the weather (causing varying degrees of back-bow/relief depending on where you started) which can “jack out” the frets over time.  Gluing in the frets helps prevent this.  I use normal Titebond to glue in the frets and run a fine bead from a fine nozzle over the fret slot and then press the fret in on top. The Titebond lubricates the fret in.  If I’m being really pedantic, because I fret the board off the neck, I can clamp it in slight positive relief overnight, which means the barbs have time to press into the slot sides and set there, and the board comes out flat in the morning (no back bow) ready for gluing to the neck.

 

If I ever need to replace a fret, the soldering iron trick means it comes out pretty easily and the set glue in the end grain of the wood helps prevent chipping-out. 

 

EVO fretwire (my preference) has short tangs compared to other stuff around and also a radius between tang and crown (as do most wires) so a bevel on the top edge of the fret slot is necessary.  The EVO therefore needs good technique because there is not much grip length for the barbs and gluing helps a lot.  The Titebond sets harder than the wood and I don’t buy into the arguments about it creeping etc.. If used right, with a thin glue line, it works at least as well as any other glue."

Cheers,

Brian

[Russell Vance]

Hi All,

Brian refers to Trevor Gore mentioning that  pressing in frets as an accurate way of seating frets which eliminates most post fretting adjustments.  Hammering in frets and dressing is acknowledged as a time honored and common practice but as we have never done it I cannot comment on it.

I'll offer my observations of what I know if anyone is contemplating pressing in frets (and we also glue everything with CA as mentioned previously).   Firstly, the advent of machined aluminium  20 inch cauls .has allowed for very accurate fingerboard surfaces.  We machine  initially with a shaper head  and vacuum jig and then mill the back of the the board to flatten the board as it responds to being radiused on one side and needs to be reflattened.    We then glue boards on using a radiused caul to keep the board and neck as flat and true as possible while the glue cures and refinish again with the radius cauls before fretting. 

We use JESCAR Stainless wire as standard and buy it in coils pre-radiused from the manufacturer (with a surcharge for our radius) which we find gives us a  consistent wire radius and less waste than other packaging. We do not  over radius frets - if everything is accurate then there is no technical reason for anything other than total consistency with identical fret, board and pressing caul radius matches.

We use a standard two ton press and brass radius inserts available just about anywhere these days.   Our fret slots are either .023 or .025 for rosewood and ebony respectively and template/machine cut.   The historical result has been 80% or better of frets require no dressing or touch ups with most of the factory crowns being largely intact. The success rate with the occasional nickel silver fret requirement has not varied from this figure and as we hand roll our nickel silver I was a little, and happily, surprised with this bonus result.

Brian also mentions the fret tangs as something to consider:  the tang width and depth can vary greatly with the fret type and this will cause variable to creep in - for instance;  jumbo wire generally has  a deeper tang and sometimes wider tang causing  a greater degree of compression in ebony but virtually none in rosewood. This is not a major consideration if using a dual action truss rod as this compression will tend to bow the final glued up neck but may need to be compensated for with single action truss rods.

Also, when pressing into quality ebony there is a wider latitude for applied press pressure whereas pressing into rosewood is a more judicious exercise to achieve consistent seating with no underfret crushing or witness marks (which most of us repair guys have noticed when pulling frets).

My main observation is that the use of tight tolerance aluminium cauls to finish boards both in end to end flatness and radius and subsequent use of a press is a major contributor to accurate "one hit" fretting.

This is basic information and for some of us its old hat and there are no doubt better ways and certainly more sophisticated jigs and machinery.  However, for our production numbers this is efficient and cost effective. 

For information only.

Regards, Rusty.  

[Glen H]

I have sure learned several things from this discussion! Thanks for the questions, answers and follow up on this topic. My last completed build was number 23, and did have some headaches with frets. It’s my first time to really run into fret issues. Some tips I’ve gleaned here, i’m sure will prevent issues in my future builds. Thanks