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Simple Truss Rod Install, Masked Luthier
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Author:  Dickey [ Sun Jan 08, 2006 2:30 pm ]
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Okay, here are a few shots of installation of a simple compression rod from LMI. Four necks so far and no problems, this is number five.



This 1 1/16" stop is predrilled at 3/16" the rod size. The washer is squared on the bottom and slightly on the top. Two small holes are drilled either side of the stop end to provide bearing for the washer. The stop is glued into position. Rod slot done easily on the table saw 3/8 deep by 1/4 wide.



The hook end, showing the dovetail. A 3/16 hole is drilled at the angle formed on the truss rod end, fits well on down in the shaft.



.25 inch spline gets glued in here. It's proud by an 1/8th inch and will get planed flush then sanded. Refer to the first photo and you can actually see the precut spline laying on the bench.



Headplate glueup, rosewood on Mahogany, lots of Klems on this job. Hard to beat a good cam clamp.

Dickey38729.5931365741
Author:  Steve Kinnaird [ Sun Jan 08, 2006 2:37 pm ]
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Bruce,

Is that rod arched, or would that be arced? Oh heck, is it slightly bent? You know, to try to straighten itself out when tightened????
Next--how well does it work?

Steve
Author:  Dickey [ Sun Jan 08, 2006 2:45 pm ]
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Straight as a string, except for the J hook on the end. It is the simplest rod on the market, covered with shrink wrap to help dull a rattle. It has controlled each of the last four necks no problem. Stability in a neck is what we look for in addition to getting the correct relief. No problems with the last four. It seems to do the job it was designed to do, counteract the string tension for years to come, while providing adjustability.
Author:  Steve Kinnaird [ Sun Jan 08, 2006 2:47 pm ]
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Thanks Bruce.
I bet they don't cost an arm and a leg either, huh?

SK
Author:  Dickey [ Sun Jan 08, 2006 2:54 pm ]
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This is old stock but, ten bucks, comes with nut, washer, and allen wrench. LMI compression rod. 3/16 inch steel shrink wrapped in plastic straw.



TRES LMI Compression Truss Rod

Looks like Q of three is 11 bucks now.Dickey38725.9586111111
Author:  Alain Desforges [ Sun Jan 08, 2006 3:19 pm ]
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   Lucky young man. I would of loved to start that young...
Author:  Rod True [ Sun Jan 08, 2006 7:09 pm ]
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[QUOTE=Alain Desforges]    Lucky young man. I would of loved to start that young... [/QUOTE]

What? Dancin' or Luthin'
Author:  Rod True [ Sun Jan 08, 2006 7:14 pm ]
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Bruce, I guess cutin' the channel on the table saw makes this very simple, no jig to cut a curved slot like most do with the single action rods. I like it. $10 isn't to bad, although I can get 12' of stainless rod for $12 canadian and just heat and bend, cut the thread and there you have it, just need the nut and washer. That's what I do anyway, but I have been cutting the slot with a curve. Basically like Charlie Hoffman.Rod True38726.1362731481
Author:  Arnt Rian [ Sun Jan 08, 2006 9:45 pm ]
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Interesting. I have made some guitars and mandolins with the Gibson style single rods and brass nuts where the cavity for the nut and washer is in the peg head. This makes the neck quite fragile in this area (as many Gibson owners know). You anchor the washer in the neck and avoid having to scoop out so much wood in the peg head which should make the assembly more solid. The question is how it will hold up over time and how easily you can access it if repair becomes necessary. The straight rod will work well, the deeper it is buried in the neck the better in my experience. I aim for about 3 mm (1/8”) of wood under the rod all the way up the neck, which means I must shim the neck blank at the nut end with the same amount as the neck depth taper when I cut the slot on my table saw.
Author:  Alain Desforges [ Sun Jan 08, 2006 11:19 pm ]
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   Rod, BOTH!!!
Author:  Laurent Brondel [ Mon Jan 09, 2006 1:59 am ]
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[QUOTE=Arnt]This makes the neck quite fragile in this area (as many Gibson
owners know).[/QUOTE]

Yes, having the truss-rod nut at the peghead is very tempting because it is
so much easier to adjust than under the fingerboard extension with the
strings on. The LesPaul peghead crack is a classic… But I'm wondering,
considering the light weight of an acoustic, if it's reallu an issue. A lot of
builders, Sobell, Sexauer etc., use the peghead truss-rod nut so… Is the
compression rod as effective as the "regular" Martin rod?
Author:  Mark Swanson [ Mon Jan 09, 2006 2:11 am ]
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Just like Rod, (a good name for a subject like this) I make my own rods from the 3/16" steel. It's easy. I use the Gibson-type nuts from Stew-mac. I also use a curved channel, and I think the rods work a bit better that way. I think they make a good rod, and the necks are lighter when you use a rod like this.
Author:  Dickey [ Mon Jan 09, 2006 5:00 am ]
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Mark, Do you find the curve in the channel induces a gentle curve for relief? To me, the upper part of the neck is weaker, due to the tapering neck. That allows the upper part to be more greatly affected with either forward or backward adjustment to string tension and the truss rod.

I've done just one of the Martin Rods in my HD28 but four of these straight in a straight-cut channel. So my experience is limited, but no problems after a couple years in play.

Author:  Rod True [ Mon Jan 09, 2006 5:22 am ]
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Bruce, think about the rod being bent before you tighten it up. With just a straight rod, you are trying to bend it and the neck. With the curved channel the rod is already pre-bent so when you tighten it, the rod wants to go straight.
Author:  Rod True [ Mon Jan 09, 2006 5:27 am ]
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Laurent, you can really move the neck well with the compression rod. You can also use the stew-mac hot rod and install it for head stock adjustments (I've never used one, but I would bet there are others here who have).
Author:  Rod True [ Mon Jan 09, 2006 5:30 am ]
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Bruce, I do like the little allen nut (bullet nut similar to the ones that Stew-Mac sells) at the adjustment end, much less matterial to remove than is required for the gibson style brass nut. I may have to try that. Just need a Canadian source for the nut.

Author:  Dickey [ Mon Jan 09, 2006 6:55 am ]
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Rod, You got a pic of that curved spline?

I think they call it a compression rod because that is what it is doing. Installing a curved slot and spline causes it to leverage against the thin neck cavity and fingerboard, doesn't it?

I held one of Charlie Hoffmans Cocobolo Jumbos this summer, he does it just as you described too. There was nuttin' wrong with that guitar. What a craftsman.

I'm thinking about what the wood is doing under stress. Strings pull the neck forward, so we have to offset the torque forward with torque backward. When we bend wood on a side bender, aren't we compressing some cells while elongating others? Of course they take on those shapes permanently.

In the neck, we simply require the wood to stay to the point needed then hope it stays stable. If not we tweak it and hope to have enough adjustment either way to do the job. Just wanted to show a simple way to truss a neck.

I recently purchased a dozen Martin Rods with the u-shaped Aluminum channel, so after a run of 12 I'll do 12 the Martin way. The great thing in hand building, you can quickly try other methods and materials. Maybe I should switch at 6 ?? Makes sense.Dickey38726.6295023148
Author:  Rod True [ Mon Jan 09, 2006 1:09 pm ]
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6 of one, half a dozen of another

Bruce, I don't have a pic of the spline. The slot is level from the end of the neck to the 7th fret cut 1/2" deep, than curves up to 5/16", so the curve is gradual. I have made a simple ramp to cut the channel, based on a very old design of Mark Swanson's (he now uses a pin router I think). Clamps to the side of the neck and run the router down the center.
I use the same jig to draw the curve on the spline, than rough cut on the bandsaw and sand to the line, than glue it in same as your pic, plane/sand flush to the top of the neck.
Author:  Mark Swanson [ Tue Jan 10, 2006 3:03 am ]
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I agree with Rod, this kind of rod has a lot of adjustment action and the curve helps it work better. The upper part of the neck does seem to move more than the part closest to the body.
I like to use the Stew-mac bullet nuts for electric guitars. Here's a shot of one I am working on right now. You don't need to route out such a large section for the nut, I cut out just enough to make room for the nut. and I don't use a cover at all. For an electric guitar I think it looks just fine.
I do use a pin router set up for making the slot. Works good! Cutting the curved channel can be a challenge.
Author:  Dickey [ Tue Jan 10, 2006 3:42 am ]
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Very Nice Mark.
Author:  Arnt Rian [ Tue Jan 10, 2006 6:28 am ]
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Hi Mark, I think that it looks better than "just fine", in fact I think it looks great! Anyways, do you have a snapshot or two of your pin router set up?
Author:  Mark Swanson [ Tue Jan 10, 2006 6:47 am ]
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Thanks, Arnt! I don't have a shot of it....and it's a mess right now.
But I can tell you that I built an LMI-style binding router jig. I have adapted it for use as a pin router as well. You need a way to lock the mechanisms' up/down movement, and a baseboard that has a pin centered in the right spot.
I have a platform on which I clamp the neck on its side. This has a base that is curved in the way I want the channel to be and that follows the pin in the table. I use a 3/16" slot cutter bit to route the slot.
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