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May 18, 2021 - 11:53:44 AM
4064 posts since 1/21/2003

I own a Williams Kenny Ingram Special, #9, which I picked up from Will in '07. It's my go-to banjo since then, even tho I haven't had a gig since early 2020 due to the pandemic. The band I'm in (The Notorious Shank Brothers) is getting together just to jam next week & due to the fact that I haven't been playing, I started practicing recently.

When I did so, I noticed that the Flying Eagle inlays had risen above the fingerboard, either from the inlays rising or the fingerboard shrinking. I will try to take some pix later today. I asked Arthur Hatfield, who made the necks, about it & he said that Custom Inlay did the inlays. I just wonder if anyone else has had this problem and, if so, what did you do about it, if anything. Thanks...

May 18, 2021 - 1:03:41 PM

beegee

USA

22371 posts since 7/6/2005
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Usually that would indicate that the fingerboard has dried and shrunk. If the inlays are still tight, that's what I would suspect. How many thousandths are they proud of the fingerboard?

The down and dirty fix would be to sand them down flush. Unfortunately that may leav the inlays too thin. The proper way, if the fingerboard has shrunk, would be to remove the inlays, deepen the cavities and re-glue. Either would require a re-fret.

May 18, 2021 - 1:53:11 PM

4064 posts since 1/21/2003

Bob, I have no way of measuring how proud they are but if I use my finger on the pearl, I can feel the drop down to the fingerboard. If I had to guess, I would say they're maybe 3 or 4 thousandths drop to the FB. I can feel them but they aren't doing anything with my playing. I do oil the FB once or twice a year.

I took some pix but am having trouble uploading them. Give me a while...


 

May 18, 2021 - 1:54:33 PM

13589 posts since 6/29/2005

The old Gibsons had the inlay cavities cut all the way through the 1/8" fingerboard, then the pearl, backed with poplar to equal the fingerboard thickness was inlaid so the pearl was flush. If the poplar expanded more than the fingerboard, the inlays could possibly come up proud, but not by much, and I've never heard of it happening, but those fingerboards would be over 90 years old, so stabilized and worn.

Rosewood is unlikely to shrink very much unless it's green, which is unlikely, and MOP doesn't expand.

I don't know how much they stick up—one or two thousandths?  If the proud inlays cause buzzing, I'd level them, but short of that, I'd ignore it.

If the person who did the fingerboard is reading this thread, they know what they did.

May 18, 2021 - 1:57:52 PM

4064 posts since 1/21/2003

More pix...


May 18, 2021 - 2:04:09 PM

4064 posts since 1/21/2003

Ken, this fingerboard is rosewood, maybe good rosewood, and Custom Inlay did the work on the FB. No buzzing at all & I can feel the difference but it doesn't affect my playing. Thanks.

May 18, 2021 - 2:06:32 PM

4064 posts since 1/21/2003

One more photo...


May 18, 2021 - 2:07:42 PM
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4064 posts since 1/21/2003

These pix are hard to see what the problem is but the best I could do...

May 18, 2021 - 3:43:43 PM
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1622 posts since 7/2/2007

It looks like there is a ridge of glue being squeezed out around the perimeter of the inlays, that in the pictures looks higher than the inlay.

Wood, like in the fingerboard is always moving. Over many years it settles down some but never quits. The shell is much more stable.

I've heard though never experienced that quick set epoxy stays a little softer than slow cure. In that regard, I've heard of inlays being pushed up by quick set epoxy. I actually called a mfg and asked about that. They said it was possible slow set epoxy could swell from exposure to water but relative humidity would have to be over 90% for long periods for it to happen outside of actually getting wet. Unlikely for a banjo, we hope!

However, the constant shrink swell of wood can do some strange things over time. I've seen tight fitting wood joints with invisible glue lines actually extrude a line of yellow carpenters glue after 30 or so years. Where it feels like a slight ridge along the glue line. Other woodworkers have confirmed this even though it sounds hard to believe. On well used furniture, it is usually worn off so you'd never notice it.

Another phenomenon I've run into is a reaction with oil stain and some glue. Where the oil being a solvent can be absorbed by some glue causing it to swell or soften. Most glue is designed to be water resistant but it would be unusual for it to be made to be oil resistant more than to withstand a single exposure like when a piece of furniture is stained prior to finish.

Your fingerboard looks great, and the wood looks kinda well oiled. I suspect the glue used for the inlay is absorbing the oil you are using on the fingerboard and swelling up.

If it gets in the way of looking good or your playing. I'd consider determining if it is at least in part an extruded glue ridge around the inlay. If it is, it could be scraped flush with a razor blade and polished up with fine steel wool or a fine scotch brite pad.

Builders can help avoid this by not bedding inlay in a bunch of epoxy or carpenters glue to keep the glue to a minimum.

In your case, I'd quit oiling the fingerboard.

I'm surprised more fingerboard binding doesn't get into trouble with oil treated FB's because the type of glue often used for binding can be susceptible to being degraded by oil which is a solvent.

Anyway, most of this stuff I've run into so I'm not making it up.

Good luck!

May 18, 2021 - 5:36:39 PM
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13589 posts since 6/29/2005

from the look of the close-up pictures, it's the filler around the inlay that's sticking up and not the inlay itself.

The inlays appear to be so perfect, I'd guess they were cut with some kind of laser or CNC with a cavity program to exactly match, leaving very minimal infill. This may sound weird, but it's so perfect it makes me think the slight vagaries or inconsistencies you get with hand-cut inlays and cavities that have the edges filled with some filler like epoxy or CA mixed with fingerboard sawdust may stay flatter and bind the inlay in better—I know I have never had any filler come up like that.

May 18, 2021 - 6:15:31 PM

4577 posts since 9/7/2009

I agree, from the photos, that it is the filler glue that has swollen. I had the same thing happen with one of the first inlays that I did on my personal banjo using fast set epoxy.  It swelled up around the inlays after a year or two. I just scraped the excess away with a sharp knife. I don't use fast set anymore.  

May 19, 2021 - 5:10:53 AM

13589 posts since 6/29/2005

quote:
Originally posted by BNJOMAKR

I agree, from the photos, that it is the filler glue that has swollen. I had the same thing happen with one of the first inlays that I did on my personal banjo using fast set epoxy.  It swelled up around the inlays after a year or two. I just scraped the excess away with a sharp knife. I don't use fast set anymore.  


Marvin—what kind of fast set epoxy did you use?

I just started using System 3 fast set mixed with black/brown tint and fingerboard sawdust a couple of months ago and so far haven't had any trouble, but it's early days and I'm getting a little nervous, especially concerning peghead inlays that are finished over.

May 19, 2021 - 6:18:12 AM

4577 posts since 9/7/2009

quote:
Originally posted by Ken LeVan
quote:
Originally posted by BNJOMAKR

I agree, from the photos, that it is the filler glue that has swollen. I had the same thing happen with one of the first inlays that I did on my personal banjo using fast set epoxy.  It swelled up around the inlays after a year or two. I just scraped the excess away with a sharp knife. I don't use fast set anymore.  


Marvin—what kind of fast set epoxy did you use?

I just started using System 3 fast set mixed with black/brown tint and fingerboard sawdust a couple of months ago and so far haven't had any trouble, but it's early days and I'm getting a little nervous, especially concerning peghead inlays that are finished over.


Ken, it was some that Stew Mac sold back in the late 70's early 80's. I don't remember the brand. The glue was in two syringes, side by side, that had two plungers that were pushed at the same time to dispense the glue, and then mixed. At that time, they sold both slow set and quick set. I found the same glue at our local hardware store. I'm sure there have been improvements since then, but looking at the pictures above, maybe not.

May 19, 2021 - 8:01:38 AM

1622 posts since 7/2/2007

I think the best preventative measure is to make shell inlay fit the cavity well reducing the amount of glue necessary regardless of type of glue. I prefer epoxy to set inlay and either use the black StuMac epoxy for ebony and for other woods have found that Behlen Master Furniture Powders work great for adding color to epoxy. More powder = darker, less = lighter.

Burnt Umber is almost universal and can match up adequately with rosewoods to cherry or walnut. On the lighter woods, clear epoxy can be the best choice.

I've never had much luck using even the finest sawdust. It immediately changes color when the glue wets it, makes too thick a paste, or just plain won't fit in the space around inlays for me.

I used quick set epoxy to glue on a couple peghead veneers years ago but learned to prefer slow set. I work slow anyway. I've also had quick set epoxy turn yellow/brown over several years in some non-instrument applications but another reason I shy away from it in instruments.

Some epoxy is too thick to even squeeze out adequately on some larger joints. Some epoxies also release something called amines as they cure that can interfere with some finishes. I ran into that using epoxy as a pore filler on guitars a couple times. I learned a wipe down with naphtha after epoxy application but before any sanding helped with that (I also heard a wipe down with a damp (water) cloth also works. Now I use an epoxy that is designed to eliminate amines.

My current favorite epoxies are System Three general purpose resin with medium hardener for instrument gluing. It is thin enough to allow adequate squeeze out even for layered headstock veneers. And System Three Silvertip with fast hardener for pore filling, it supposedly eliminates amines (I still wipe it down).

That's what works for me at least for now. Glue use has been an ever evolving process in my shop.

May 20, 2021 - 2:08:24 AM

5steve

USA

1257 posts since 11/24/2005

I have the same problem on a Stewart Mac Kit I built in the early eighties . I used the same epoxy I had to trim the epoxy filler around the edges of some of the inlays a few years later, some of te inlays protrude slightly after the epoxy expanded and needed resanding.
I think a couple of the small ones up the neck still protrude a little. Steve

May 20, 2021 - 4:20:25 AM

15198 posts since 12/2/2005

quote:
Originally posted by Ken LeVan

The inlays appear to be so perfect, I'd guess they were cut with some kind of laser or CNC with a cavity program to exactly match, leaving very minimal infill.


You're exactly right, Ken. That's precisely how Custom Inlay does it. It's a fun place to see if you ever have the chance.

Edited by - eagleisland on 05/20/2021 04:20:51

May 20, 2021 - 5:56:10 AM

13589 posts since 6/29/2005

I must admit that in 55+ years of fingerboard making, I have never had a problem like the filler rising out of the gaps, and I started back in the day with shellac sticks, went on to polyester
"bondo" with iron oxide filler, CA with fingerboard dust, and now epoxy with fingerboard dust.

I sincerely believe the epoxy is not the culprit —it's a problem of expansion and contracting of the wood fingerboard caused by too tight a fit not allowing for uneven expansion and contraction—Any woodworker learns that—woodworking 101— and furniture construction must allow for it.  The wood expands at a vastly different rate than the MOP— I just sent an email to System Three asking what the expansion rates are for General Purpose epoxy and the 5-minute kind are, but I know what the answer will be— it's going to be unmeasurably minimal in the .050" thickness of an MOP inlay.

Like RBUDDY said, glue is an ever evolving thing in my shop, too.  I use 8 different kinds of adhesives, 9 if you count Super 77,

I use epoxy for everything that has to do with fingerboards and peg heads because epoxies contain no water and stay flat. I use the System Three general purpose for a number of things ranging from casting to adhesive. In terms of adhesive, I used to use the T-88, but now I use the general purpose with medium fast catalyst, and add colloidal silica and wood flour to thicken it, which is recommended for use as an adhesive—otherwise, it gets sucked ibn to the wood and you have to coat both surfaces.


I make complex fingerboards incorporating side markers as cross-banding, usually consisting of 28 pieces of wood. 

If I would use Titebond for this, the fingerboard assemblies would cup (a "poor man's radiused fingerboard")—the ones laminated with epoxy remain dead flat.

In terms of inlays, I cut them all by hand with a jeweler's saw and, so there is never a perfect fit.  I currently use System Three 5 or 15 minute with tint and sometimes sanding dust from fingerboard wood OR iron oxide pigment that's sold in 50# bags to tint concrete—black, yellow ochre, and red ochre in some combination will match any dark wood.  The tinted epoxy will also fill around metal inlays, like copper or magnesium, which expand and contract much more than MOP and require a larger gap. The epoxy filler has just enough flexibility to not crack from expansion, and has an added advantage of filling the recesses in engravings.

May 20, 2021 - 9:14:48 AM

1622 posts since 7/2/2007

It's interesting Ken that we have moved in similar directions in glue use, even to some of the same brands. I gave up on T-88 because I found it too thick for my liking. But I use epoxy for all thin lamination's as in layered head plates, back straps and also for gluing down fingerboards. All for the same reasons you've illustrated.

I disagree with epoxy being a flexible filler around inlay though at one time I thought quick set had a benefit in that regard and I probably used it for a few inlays. Used as an expansion joint the glue would have to go somewhere and up and out is about the only direction I see available.

I've yet to have any problems with inlays or epoxy and the tightest recess's I could accomplish other than leaving enough room to get the shell in or out w/o breaking.

Adding to the complexity of all this is metal moves with temp, and wood moves with humidity.

I remember looking up specs on metal expansion and it seems like metals we might inlay would only change in dimension by less than 0.001"/inch over 50 degrees in temp range. Shell I expect is even less than that. (Do your own math)

So the real mover is probably the wood which across a good quartersawn fingerboard of 2" in width could move around 1% over a 50% RH change which would be up to 0.02". Or about 10X more than metal or shell in a typical instrument environment.

In length, wood changes very little. Surprisingly, if I remember correctly a 3' precision metal ruler moves more in length over a typical temp range than a good wood yardstick does in RH fluctuations.

These are the kinds of rabbit holes people who take this luth stuff seriously end up exploring.

This has been a good discussion where everyone is sharing what they have learned over years of wood work.

I thought Erik's issue may be related to the glue absorbing the fingerboard oil but looking up epoxy resistance to common oils used in fingerboard preps, it is pretty good so that can probably be ruled out.

But the glue is coming from somewhere, and is obviously moving to some extent.

May 20, 2021 - 9:21:27 AM

13589 posts since 6/29/2005

I got an answer back from System Three, and their (and probably most other) epoxies shrink max 2% during cure, the larger the mass, the greater the shrinkage. After cure, they are dimensionally stable, so epoxy expansion coming out of the joint because of the material is impossible—it's more likely the joint would sink during cure because of shrinkage.

May 21, 2021 - 4:52:11 AM

13589 posts since 6/29/2005

Here's another thing to consider: 

In researching expansion / contraction rates of epoxies. etc., I noticed that some materials you would use as inlay fillers have a heat deflection temperature of 101 deg F.  Meanwhile, wood will expand at the high humidity we experience in many places in the summer that can reach that temperature.

A banjo in a black case in the summer in let's say Louisiana, will have the wood of the fingerboard expanding across the grain into the filler which has exceeded the heat deflection temp, and squeeze it against the MOP which would have a different expansion contraction rate.

If the inlay was fitted very tightly, there would be no "wiggle room" and it could make the filler move up (no room for it to go down).  If the inlay was glued in, whatever it was glued in with might also soften and "go with the flow". I could picture that happening.

Edited by - Ken LeVan on 05/21/2021 04:58:10

May 21, 2021 - 6:38:05 AM
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hbick2

USA

357 posts since 6/26/2004

For what it's worth, Harry Sparks and I had a banjo shop in my basement in the latter half of the 1970s. We mostly were making replacement necks for Gibson banjos. We had Bill Sullivan make our neck blanks using our specs, including thinner Brazilian rosewood fingerboards and a slightly different angle on the heel cut. We purchased our inlays precut.

During that time, all of our inlaying was done using a Dremel tool with a leveling table, and occasionally a small chisel. We glued our inlays in using white glue. I believe it was Titebond. As a filler, we used Plastic Wood. For color, we used burnt sienna oil based artist paint (the kind that comes in tubes) for rosewood fingerboards and India ink for ebony ones. We would put some Plastic Wood on a mixing board and use a spatula to mix in the color thoroughly. Then we would mash it in around the inlay and leave it heaped up to account for shrinkage. We then sanded it flush. After fretting, we oiled the fingerboards with boiled linseed oil.

This may seem old fashioned considering today's luthier thinking, but it was simple, quick and it worked. And it lasted. I am attaching a photo of several inlays in my own banjo. This neck was made somewhere around 1978, which makes it over 40 years old. Nothing has been done to it since except for a periodic oiling. I'm pretty happy with the way it looks. Whether it will look like this 100 years from now, who knows? But I won't be around to see it and the warranty will have long since expired.

Harry


May 23, 2021 - 10:36:37 AM

1622 posts since 7/2/2007

I find it pretty hard to fathom the idea tighter fitting inlay (less filler) could lead to more glue being pushed out of the filler line than a wider filler line being used as an expansion joint. How do you get more from less?

Every critique of fine inlay work I’ve ever heard of hinged In large part on quality of fit.

In my experience, in complex shell inlay, shell pieces are not installed with spaces between them intentionally. Unless it is part of the design.

The pictures look like there is as much filler as anyone would want, more than I’d like. For that much glue to come up, it has to come from somewhere.

I agree a hot car could be a contributing factor, good point Ken. We all know heat softens epoxy.

May 23, 2021 - 1:14:38 PM

13589 posts since 6/29/2005

quote:
Originally posted by RBuddy

I find it pretty hard to fathom the idea tighter fitting inlay (less filler) could lead to more glue being pushed out of the filler line than a wider filler line being used as an expansion joint. How do you get more from less?

Every critique of fine inlay work I’ve ever heard of hinged In large part on quality of fit.

In my experience, in complex shell inlay, shell pieces are not installed with spaces between them intentionally. Unless it is part of the design.

The pictures look like there is as much filler as anyone would want, more than I’d like. For that much glue to come up, it has to come from somewhere.

I agree a hot car could be a contributing factor, good point Ken. We all know heat softens epoxy.


I know it's hard to accept that there can be such a thing as an inlay that's "too tight", but as a lifelong woodworker, I can attest to the fact that joints can, in fact, be too tight—especially with dissimilar materials.

I don't know who said "perfect is the enemy of good", but "Just right" in woodworking means allowing for inevitable movement, not difficult in hand work, but it's easy enough to step on the compulsion roller-skate with the computer generated stuff.

Full disclosure—you can disregard what I say—I'm old school, in the camp with Harry (HBICK) of a previous post and am not particularly respectful of computer generated inlays and can see them from three feet away. The day I seriously consider buying a CNC is the day I should stop making instruments.

May 23, 2021 - 5:37:41 PM

165 posts since 10/8/2006

Many epoxies use a nylon filler or "bulking agent", especially if attempting to bulk up one part of a 2-part system to achieve a 50/50 mix ratio.  But, the nylon can attract water from sweat or the atmosphere, causing the inlay filler to expand as in Eric's photos.  It can be sanded flush, but then if things dry out the epoxy will shrink and cause a slight depression around the inlay.  My old Erika Banjos shop was next door to an aerospace adhesives company, and they worked with me to develop a couple of 50/50 epoxy systems (AMR 101-M and AMR 101-Flex) which contained neither a solvent nor any nylon and we sold a lot of it back in the 1970's, but the company closed and production ended.  I have 2 banjos from back then and the inlays are still perfectly flush.  Some types of cyanoacrylates can also be affected by ambient humidity even after they cure.

Even on flat fingerboards it's become customary to use thicker .060" shell (rather than .040" or .050" as in the past), so sanding down several thousandths should be safe enough without risking getting the MOP too thin.

May 23, 2021 - 6:35:16 PM

1622 posts since 7/2/2007

@Ken LeVan

Hi Ken

First, I haven't heard your explanation of where the glue came from that was extruded around an inlay you suggest was too tight, from the pictures it is more than a hairline. What is your preference for filler width? I don't use CNC, I think it looks somehow too sterile for my tastes, but even builders that do can dial in clearance to their liking. So this isn't a CNC issue.

Second, you are implying that Custom Inlay did not allow enough clearance around the inlay as a cause of the problem. Remember, they do more inlay work than anyone posting here, probably more than all of us combined, and the notion they don't have this down to a science is to me far fetched. I think there is something other than fit going on. Possibly a hot car experience as you suggested.

Third, you suggest I find some basic fundamentals of woodworking hard to accept.

Back in the 70's I was working in a high end custom furniture shop and we shipped furniture as far as Europe and also did custom casework for museum displays. As the shop foreman I was responsible for designing and ensuring construction methods that minimized potential problems with wood movement in variable environments. I'm not at all new to this, I specialized in it. I built my first stringed instrument in the early 90's. In the late 60's I had jewelry in an exhibit in the Detroit Museum of Art.

I always make my inlay fit as tight as possible, of course there has to be some clearance, and to depth within a couple thousands of an inch, and have not had any problems. It takes a lot longer to do the fitting with X-Acto knives and mini chisels and carving tools so points in an inlay go into points in the cavity, but that's what I like. I slightly undercut the perimeter of the cavity with a knife to make final fitting easier, more accurate, and to lock in the glue. I hand cut my own inlay other than dots or diamonds.

It would be MUCH easier to rout out a cavity and float an inlay into "filler" without all the hand tool work. However, if I can see filler around an inlay without magnification, I find it objectionable. Just my preference, so I try and avoid that.

Luckily we can all choose our own methods. And with a little care we can express our personal opinions with respect for other builders and not be disparaging.

And Ken, I appreciate your posts and really like your design and execution, exceptional work!

Cheers

May 23, 2021 - 6:44:10 PM

1622 posts since 7/2/2007

Thanks for the explanation Chuck. That's the most plausible yet in my opinion. Being the Duke, you should know.

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