Official Luthiers Forum!

What is your truss rod of choice for steel string guitars?

Links appreciated.

Thanks!

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P A U L B U R N E R
Burner Guitars

I used a dual action rod by Mark Blanchard on my first build, and it is a beautiful piece of engineering (the rod, not the guitar)

However, in future builds I intend to use shop made Gibson style single action compression rods, straight, no curve. I have a gut feeling that a guitar neck will perform at its best when it is subjected to a balanced stress, with the tension of the strings equalized by the tension on the truss rod.

I've only built five reinforced necks, but I've never used anything other than a one-way compression rod. Works fine for me. One of my necks is coming up on about 18 years old and it's still doing fine.

I'll add that I put the rods in with the heel end a little deeper than the head end. I temporarily glue a thin (about 1/8") shim to the neck about where the nut will eventually be. Then I run the neck over my table saw in both directions, to center the slot. I use a scratch stock to round the bottom of the sawn groove, and I scratch a little curvature in, too. I wrap the rod with teflon plumber's tape (one overlapping wrap) to cushion it against possible buzzing. Then I press it into place and glue a spline over it. When I'm done, the rod is snugly encased in the neck, but not glued in place.

I've used Martin, Stumac, and LMI two way truss rods, all with good results.

At the moment I'm using the Martin two-way. Uses a shallower channel than the Allied, requires no filler strip, and has a reputation for being bullet-proof.

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Steve Smith
"Music is what feelings sound like"

martin style both 1 way and 2 way
won't use anything else

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Could you expand on this? I have been looking for a good way to center the slot and I can't quite picture what you are talking about. Thanks!

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Pat

I'm fond of the Blanchard rod as well and love the geared-like action resulting from the very clever use of two different coarsenesses of threads. I also like not only how smooth it is but how precise it is. I hate rods that do little until they decide to budge and then move too much.

I started a thread on rods many years ago and compared some of them and did some testing too. If I recall correctly both the Blanchard rod (Allied) and the LMI rod back then weighed exactly the same. What set the Blanchard rod apart was not only the clever mechanism but it's stainless AND the weld "globs" on the sides did not need any filing to fit the channel, the LMI rod did.

Both rods look the same from a few feet away and as mentioned weighed the same too. With this style rod it's always a good idea to test the welds of the adjustor PRIOR to installing. When testing be realistic as well and don't try torquing it from an angle, straight on is how it would be used in a guitar so simulate that. Caps are also recommended with these rods.

It's worth mentioning as well that we have seen not one, not two, but at least three that I can directly recall at the moment where the Stew-Mac "hot-Rod" had split out the back of a neck. One was a brand new Luthier built, a guy many of us know from this forum Les Paul where the SM Hot Rod split out the back of his neck. We saw another one last week, or was it this week, can't remember.

Anyway at least three and likely more have had this happen and it was NOT pretty.... The SM rod is deeper and hence not as much meat left on the neck wood when using these.

I've been directly accused of being a shill for Stew-Mac before... because I basically love the company, many of the tools, see real value in their offerings, etc. and Dan is a friend. But I do think that based on what we have seen with this rod that SM should consider either a redesign or taking it off the market. Some shill I am....

SM Hotrod punched through the neck on my first acoustic-I posted photos here. That was a major suck event.

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Steve Smith
"Music is what feelings sound like"

Sorry to hear that Steve, that's four that I know of now.....

Martin style 1 way with aluminum channel as sold by Stew-Mac epoxied into the neck. Helps to stiffen neck and super solid with no worries of breakage. Being epoxied into place there are no worries of break through on back side of neck.
Tom

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A person who has never made a mistake has never made anything!!!

Epoxied-in aluminum-channel truss rod....I assume that the epoxy was applied to the sides of the channel? Thanks!

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Peter Havriluk

Yes, Pat, with regard to the shim and the table saw:

First of all, I try to center the blade as best I can, adjusting the fence for the rough width of my neck blank. However, it's very difficult to be perfect doing that. You will most likely have a slot a little off center. If you turn the neck around and run it through again, you will now have two overlapping saw kerfs that are centered on the neck. With some test runs on scrap, you can set things up to saw an almost perfect 3/16" or a tiny bit wider.

Second, the shim: This is temporarily glued perpendicular to the neck--about where your fingerboard ends at the nut. It holds the head end of your neck slightly higher than the tail end. You saw right through it.

Suppose you set your blade at 3/8". Suppose your shim is 1/8" thick. When the head end of your neck enters the blade, your groove will be 1/4" deep there. When the tail exits the blade, the groove will be 3/8" there. Your groove will be straight, but it will be ramped because the head is higher than the tail, so it's slightly deeper on the tail end. Going in either direction, it has the same effect. But here's a proviso: If your saw table is short and your neck is long, then you need an outfeed table the same height as your saw table. Otherwise, your shim will drop off the edge of your saw table before the cut is finished. See what I mean?

Yes Peter that is correct.
Tom

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A person who has never made a mistake has never made anything!!!

I have settled on the LMII TRSD two way with a 1/16" maple filler glued on top.

In 15 yrs I have used a number of rods. I have had only 2 failures and they were the hot rod and the a welded 2 way. Any rod that uses a weld or silver solder on a threaded rod , if not done perfectly will change metallurgical properties . Too much heat can make this brittle and the cut of the thread can create a strong stress riser.
I am familiar with the Blanchard rod but never used on so I have no real experience with them. As for the Gibson Compression rod or any 1 way rods are just fine if done well. When I use a 1 way I will tension the rod slightly and level the board. That way is I loosen the rod I have forward movement.
The 2 way rods , most have a smaller channel which I like . The Hot rod needs a deeper channel.

The weak point in the 2 way rods is the design of the mechanics. Martin uses a chambered cylinder and there is no weld on the threads at all and is one reason it is a great design. As you adjust the nut is will push or pull on the rod making it flex in one direction or another. I have not seen one fail yet.
Use what you feel comfortable with , and what works for you. On the compression rods , they do not rely on pushing on the neck , they are strictly in tension and like a bow string , as they are tightened they cause the bow in the neck. A simple but great design. A channel 1 way rod is a push style , as you tighten it , it bows and pushes on the neck and fretboard.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I've used the SM rods in several guitars. Just make sure you have enough wood to back it up.. Not sure how that would be the fault of the rod if it punches through the back of the neck. Broken welds is obviously a defect but I've not seen that on the SM rods yet in about 25 guitars so it's not a lot of data points but still they work for me. First few guitars I built used just steel bars and when pulling the spokeshave on one of them I exposed the metal.. Woops! Back to the drawing board.

A simple compression rod works for me. I bend and cut my own from steel that I won on an Ebay auction cheap. With over 30lbs of rods I'm good to go. I just use a 90 degree bend to anchor the end. I wrap the rod with some jute to prevent any rattle. I like a small access hole so I use the little allen head nut sold at LMII.

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http://www.cushmanguitars.com/.

A man who carries a cat by the tail learns something he can learn in no other way.
Mark Twain

What makes it the fault of the rod, the SM Hot Rod, is that the rod is marketed as a general purpose rod with no disclaimer that for guitars with lower profile necks such as Les Pauls, many electrics, and acoustics where the maker is going for a low profile there is not enough meat left to prevent blow out the backside of the neck. The Hot Rod is dimensionally taller than all other rods making this extra height a potential liability.

What makes it even worse is that when the damage happens the instrument is usually either in final set-up and brand, spanking new or damage occurs shortly there after depending on how much the rod is engaged. Anyway it fails at delivery time or shortly thereafter making it a pretty aweful experience for all concerned...

I've used the Hot Rods on my stuff too early on with no issues. But I don't want to be that guy or have my clients have to deal with a poor choice for the application of rods in the future.

Also if you have ever spent time in the world of guitar techs you know that it's not uncommon to have some gorilla really crank the thing.... Since we cannot know or control who will be servicing our stuff in time why take the chance.

Something else with the Hot Rod is that it requires a flat bottomed channel where as e.g. a Martin two-way uses a round bottom slot. This adds a bit of meat there and perhaps would make it slightly less likely to blow out on a thin neck.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

In case anyone wondered what suck looks like.

And, of course, it was not the Hot-Rod's fault but entirely mine.

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Steve Smith
"Music is what feelings sound like"

Ouch!

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Steve Sollod (pronounced sorta like "Solid")
www.swiftcreekguitars.com

So, Steve Smith, a question. Did the neck with the hot rod breakthrough have carbon fiber reinforcement also? I've know of two people who had the same experience as you, and both necks had carbon fiber. I have a strong suspicion that the CF stiffened the neck so, that it caused the wood failure on the necks when the rod was cranked.

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michael propsom
www.propsomguitars.com

Michael, the neck did have two 1/8" x 3/8" carbon fiber strips but I believe that the primary reason the rod punched through was that the wood was too thin - probably on the order of 0.080" or so. I pulled the fretboard, epoxied more wood in the bottom of the slot and put in an Allied two way rod followed by a new fretboard. All has been well since and it's my daily player. I learned long ago to always put pressure on the neck when I adjust truss rods so they aren't doing the bending.

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Steve Smith
"Music is what feelings sound like"

The three hot rod blow outs that I have seen in person did not have any CF augmentation.