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PostPosted: Tue Sep 04, 2018 5:11 am 
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Joined: Tue May 09, 2017 5:34 am
Posts: 39
Hi All

I need to re-route the truss rod channel on a Harmony 1260. I have removed the neck from the guitar because it also is going to need a neck reset (probably along with a re-fret and leveling)

I have removed the fretboard. I want to replace the broken truss rod with a dual action truss rod I bought from John Hall.

I have seen the truss rod channel jigs online but they look like they are for the initial building of the guitar and not repair.

If you have done this what do you do to hold the removed neck and rout a straight line?

Any assistance is greatly appreciated.

Thanks

-Pat


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PostPosted: Tue Sep 04, 2018 6:35 am 
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Joined: Fri Mar 03, 2006 7:09 pm
Posts: 5761
Location: Hegins, Pa
I use a box cove bit 1/4 and one 3/8
the easiest way to do this is to use a wookmate type of clamp. level off to the top and use a straight piece of plexi to designate the center line. take a few passes with the 1/4 then set set the mechanical end with the 3/8

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John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
Board of Directors of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com


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PostPosted: Tue Sep 04, 2018 7:40 am 
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Joined: Thu May 24, 2012 8:03 am
Posts: 1011
Location: Chestertown Maryland
If you are not secure in your router skills, hand tools would make it a simple job and give you a lot of confidence that you won't screw something up so fast that you don;t know it til it's done. A chisel will widen the slot easily and a hand router will deepen the slot.

I use hand tools when I can because it is less noisy, less dusty, less dangerous, more fun, and since I am in this for the process, more satisfying.

Ed
Ten fingers in, ten fingers out


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PostPosted: Tue Sep 04, 2018 7:44 am 
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Joined: Wed Aug 13, 2014 12:14 pm
Posts: 1125
The most elegant and fool-proof solution would be to build a custom fixture to hold the neck and guide the router. How you do that is totally up to you....and that's the hard part. You need to invent it. The major hurdle may be just getting your head around the idea that building a suitable fixture may take quite a bit of time, you may need to buy materials, and you'll need to spend money. You might spend a day building the fixture, and then spend 30 seconds making the cut. But you will know the cut will be correct, the first time.

But you may not have to do that. When I replaced the truss rod on my Harmony 1260, I was able to pull out the old truss rod without removing the fretboard. I was then able, with a lot of fiddling around, to pull a homemade rectangular broach through the hole and slide in a new truss rod.

The thing to take from the way I did it, I think, is that you don't need to take off very much. My homemade broach idea was capable of only minimal wood removal. The existing channel is pretty close to the size you need already. Instead of using a router, you might be able to do the job with a narrow chisel, cleaning up the existing channel. I don't know what the dimensions are of the truss rod you bought. I used one of these:
https://alliedlutherie.com/collections/ ... truss-rods
which are 1/4" wide by 3/8" high. (They are also beautifully made).

I think before I went through all the effort to build a routing fixture, I'd try a 1/4" chisel.

_________________
Everybody is ignorant, only on different subjects. -- Will Rogers
There are lots of people who mistake their imagination for their memory. - Josh Billings
Anything is possible if you don't know what you are talking about.


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PostPosted: Tue Sep 04, 2018 8:38 am 
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Joined: Wed Aug 13, 2014 12:14 pm
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Another idea just occurred to me You might be able to use a very simple router guide. Just make a custom base for your router like this. The guide strip should be a no-rattle sliding fit in the existing channel. If you're going to increase the width of the channel when you cut, the trailing section of the guide strip should be the width of the newly-cut channel.


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_________________
Everybody is ignorant, only on different subjects. -- Will Rogers
There are lots of people who mistake their imagination for their memory. - Josh Billings
Anything is possible if you don't know what you are talking about.


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PostPosted: Tue Sep 04, 2018 4:20 pm 
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Joined: Thu May 24, 2012 8:03 am
Posts: 1011
Location: Chestertown Maryland
The most elegant and fool proof method would be to use one of these:

http://www.leevalley.com/us/wood/Page.aspx?p=72080&cat=1,230,41182,48945

If you get this tool, you will be able to use it for dozens of applications in woodworking (look up Paul Sellars), and several in guitar making (see below for 2 examples).

These are always available on ebay, and I may even have a couple to chose from in the basement. It is nice to have a small one (like the one in the shots) AND a large one, but I think the medium sized one in the Lee Valley catalog above would be a good compromise.

Elegant because it is hand powered and probably will take less time that using a powered tool, and foolproof because it is very hard (near impossible) to make a significant mistake.

Ed


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PostPosted: Tue Sep 04, 2018 7:25 pm 
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Joined: Tue May 09, 2017 5:34 am
Posts: 39
Thanks everyone... I am doing it by hand with a small chisel - little by little opening up that channel to accept the dual action truss rod. It looks like its working pretty well. I am test fitting it and its almost ready to go in except for the adjustment nut end which I will work on next.

it looks level but it is a little lower than the edge of the channel - about 1/16th. The edges of the channel are not pretty but it will be under the fingerboard - I will smooth them out to not interfere with the board when I glue it back on.

That plane looks cool - If I end up doing a bunch of these things I may pull the trigger on one.


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PostPosted: Tue Sep 04, 2018 8:21 pm 
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Joined: Thu May 24, 2012 8:03 am
Posts: 1011
Location: Chestertown Maryland
I was recently involved in a thread on another forum where I asked the question "why put a filler strip on top of the truss rod? It just means you have to dig a deeper slot in the neck, making it less structurally sound"

Probably 75% wrote back that they do not. So I would not worry about the rod being just below the surface - at least you didn't remove enough material for a filler strip.

Ed


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PostPosted: Tue Sep 04, 2018 9:34 pm 
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Joined: Mon Jul 28, 2014 7:50 am
Posts: 602
Location: Chadds Ford, PA
If the truss rod channel is being routed in, it's hard to imagine why it should be deeper than what produces a flush truss insertion. However I usually use Martin necks and their rods, too, and it isn't unusual for the truss rod to sit 1/32 - 1/16 below flush. When that happens even though I glue the rod in, I don't want any room above the rod, so I fill and sand flush. That way any force on the rod is put to work without having to move in that tiny empty space first. Who knows, maybe that also keeps the rod from singing in its coffin.


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PostPosted: Wed Sep 05, 2018 6:56 am 
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Joined: Wed Aug 13, 2014 12:14 pm
Posts: 1125
On the other hand...
Just to illustrate that there is more than one way to do things, I fit my rods to be a moderate push-in fit to prevent rattling/resonating, and put a strip of tape on top of the channel and rod before I glue on the fretboard to ensure that no glue gets into or on the truss rod that might keep it from operating as it is supposed to. It also makes it possible to pull out the truss rod to replace it, as I had to do when the weld on a truss rod broke after I'd installed it. Replacing the truss rod was trivial.

Do whatever you feel comfortable with, which will be determined in large part by your personal experience. Because I had that successful experience of easily replacing a truss rod that wasn't glued in, I'm glue-shy. If, on the other hand, I had had a truss rod vibration problem, I'd probably be describing how I glue them in.

_________________
Everybody is ignorant, only on different subjects. -- Will Rogers
There are lots of people who mistake their imagination for their memory. - Josh Billings
Anything is possible if you don't know what you are talking about.


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