Small knot on mahogany neck

Jphb77 · #1 05-09-2019, 02:25 AM

I'm seeking advice on an issue I discovered while shaping a mahogany neck for a steel string acoustic. This is my fourth scratch build so I'm an amateur to luthiery but certainly not to woodworking which has been my livelihood for the past 25 yrs. That being said, as I was roughing out a mahogany neck, I uncovered a small knot about the same diameter as a #2 pencil. I didn't notice any trace of it or any off coloring when I bought the blank. I don't care about the appearance much, as I'm not selling the guitar. But I'm noticing fibers are pulling from it as I'm shaping the neck. It's on the underside at about the 5th fret. Does anyone have any experience with filling it or possibly cutting out a small section and gluing in a piece to match and then continue shaping? Any suggestions would be appreciated greatly. Thanks

mirwa · #2 05-09-2019, 02:36 AM

Knotts are character marks, they are also weak sections, being around the 5th would not IMO be an issue, but hard to say without seeing the knott.

If you dont like it, replace it now whilst you can, at this stage of a neck build your not really invested yet

Steve

Jphb77 · #3 05-09-2019, 03:06 AM

Quote:

Originally Posted by mirwa

Knotts are character marks, they are also weak sections, being around the 5th would not IMO be an issue, but hard to say without seeing the knott.

If you dont like it, replace it now whilst you can, at this stage of a neck build your not really invested yet

Steve

I didn't think to take a picture til after I left my shop. I'll post one tomorrow. I have the fret board glued to the neck already. I could take it off. My main concern is the surface being smooth and I still have more shaping to do. So it's looking like there will be a dimple where the knot is. So I'd like to get an idea how to fill it and if I should fill it now or when it's at the final shape. Thanks for the reply

mirwa · #4 05-09-2019, 03:15 AM

Dimples can be taken care of in the finish, subjective of course to the type of finish being used.

Steve

redir · #5 05-09-2019, 06:57 AM

Yeah that happens some times. It's the nature of wood. You never know whats right under the surface. Sounds to me like you don't have anything to worry about. I would just tighten up the knot with some thin CA.

charles Tauber · #6 05-09-2019, 08:35 AM

Quote:

Originally Posted by Jphb77

Does anyone have any experience with filling it or possibly cutting out a small section and gluing in a piece to match and then continue shaping? Any suggestions would be appreciated greatly.

Unless you are going to finish the neck in something dark, you won't be able to make the repair invisible: it will always be in the middle of the neck.

If you "stabilize" it with CA glue, you still have the pleasures of working the wood around the change in grain surrounding the knot.

Were it mine, I'd discard the neck. A few dollars of wood vs. staring at the knot in the middle of the neck for the next few decades.

Big Band Guitar · #7 05-09-2019, 09:19 AM

I found a small "live" knot in my cherry banjo neck about in the middle of the neck.

That was in 1995 I has caused no issues and it gives the neck character.

I could have started over as I had the whole tree worth of lumber to choose from. But I kind of liked it.

murrmac123 · #8 05-09-2019, 09:42 AM

Quote:

Does anyone have any experience with filling it or possibly cutting out a small section and gluing in a piece to match and then continue shaping?

You've been a woodworker for 25 years, so you are bound to have a set of Forstner drill bits.

In your situation, I would shape the neck almost to finished dimension, and then use a Forstner drill bit to cut a shallow recess, and plug the hole with a corresponding size plug ... 8mm would probably work, or you might have to go to 10mm.

The Veritas tapered plug cutter is the tool for cutting the plug. I have a full set, but they can be bought singly.

With any luck you might have a suitable small off-cut from the neck with which to form the plug, and given that it is a mahogany neck, matching the grain should be a breeze, and you will end up with a virtually invisible repair.

In any event. it's "knott" a serious problem.

perttime · #9 05-09-2019, 10:22 AM

Just an idea: if it is in the center of the neck, or very near, an inlay with contrasting wood would be cool. Something that looks intentional.

phavriluk · #10 05-09-2019, 01:14 PM

Maybe there's some lemonade available. Without a picture to refer to, my comments have, let's say, 'variable' utility. But if the knot is indeed in the center of the neck, perhaps the neck can be cut apart down the middle, the area with the knot removed, and laminations of contrasting wood installed between the two halves of the neck. All at once a nice fancy laminated neck and no knot at the same time. Provided, of course, that the knot is cut away.

I once had two cherry necks that were too narrow for the fretboard width I wanted to use, and I did what I suggested above. Both necks turned out lovely, and I had the pleasure of looking at all those nice laminations.

mercy · #11 05-09-2019, 02:14 PM

I like phavriluk's idea. as far as a plug, one of those Lee valley plug cutters are about the cost of wood to replace it.

runamuck · #12 05-09-2019, 02:26 PM

I think using a plug cutter and then a plug will make the neck weaker rather than strengthening it- that is unless the knot is loose or otherwise structurally unsound.

A plug cutter will sever the wood across the grain. Glue works well for joining wood with the grain but not across the grain.

The same would be true cutting out the knot and inlaying another piece of wood because to that requires cutting across the grain.

In my opinion, you'd need to inlay or laminate another piece of other wood the total length of the neck or replace the neck entirely.

John Arnold · #13 05-09-2019, 04:23 PM

Knots this size are common in mahogany from younger trees. That comprises the bulk of mahogany cut in the last few years.
I don't worry too much about knots this size, unless they are in a high stress area (under the nut, for example).
You indicate that the knot is chunking out during shaping. That is when you should change to a different tool. Instead of a spokeshave, drawknife, or coarse rasp, use a file, card scraper, or sandpaper.

Jphb77 · #14 05-09-2019, 05:43 PM

Quote:

Originally Posted by John Arnold

Knots this size are common in mahogany from younger trees. That comprises the bulk of mahogany cut in the last few years.
I don't worry too much about knots this size, unless they are in a high stress area (under the nut, for example).
You indicate that the knot is chunking out during shaping. That is when you should change to a different tool. Instead of a spokeshave, drawknife, or coarse rasp, use a file, card scraper, or sandpaper.

Good information. I'd imagine trees are being cut prematurely these days. I did change my choice in shaping tools after I removed the bulk. I'm a big fan of the card scraper to bring the neck to a finish. Thanks for the comment

Jphb77 · #15 05-10-2019, 02:11 AM

I appreciate all the ideas and time spent to reply to my question and post. As it turns out, after I got to my desired shape of the neck, the knot ended up being smaller and did not get any deeper or pronounced. So I should be able to fix it in the finish and isn't as noticeable as I anticipated. Thanks again!