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I'm working on a guitar right now, and I'm at the truss rod routing stage. My truss rod is LMI's TRST. It's a single action welded rod with a 3/16" square rod on top of a 3/16" round rod.

My problem is that it requires a 3/16" wide slot, and all I have is 1/4". Has anyone used 1/4" rout for a 3/16" rod, and will this work ok? I'd rather not have to buy another bit if I don't have to.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Sounds like a recipe for rattles, to me. I'd buy the other bit. Worst case - you could route it, slightly off-center, then glue a 1/16" shim alongside the truss rod. I'd use my drum sander to build it and sand it to proper thickness. At the end of the day, though, I'd probably end up doing that as a fix for a boneheaded error, rather than by design.

Mike,

If the cost of a router bit is a deal breaker, you really have the wrong hobby. This is a very costly past time.

That said, you will be very unhappy with thew rattle that results from the over sized slot. If you can't bring yourself to spring for a smaller bit, rout a quarter inch slot 1/16 off center line and glue in a 1/16 inch shim.

Well Corky, it looks like we were typing at the same time.

Cecil

Thanks for all the replies, guys. As for picking the wrong hobby, you're not telling me anything I don't already know. I'm constantly long on desire and short on cash. But I can't help it. I love to build.
Based on the advice here, I'll go and get the 3/16" bit.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Todd, good idea. I have a table saw, but it's a cheap Craftsman. The blade is also dull and in need of replacing, and I've never done that with a table saw. In fact, I don't have a lot of experience with the table saw at all. Add to that, this is the only neck or wood for a neck that i have, and I'm not prepared to risk it on something I've never done before. So I'll just go get me a 3/16" router bit.
But I need to try that with a table saw on some cheap wood at some point.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Mike,

First, try to hog it out on the table saw. You will probably be okay. If not, don't despair. If your slot is oversized, go to your local friendly hardware store and buy a roll of plumber's teflon pipe joint tape. It won't stick to anything but itself, so don't freak out when you pull the first few inches off the roll. Just wrap it around the truss rod until you have enough thickness to make the whole thing fit firmly and snugly into the slot. It'll compress, but don't go hog-wild with your wraps. Just enough extra padding there to make it snug and obviate the chance of a buzz or rattle.

This is a pretty good practice, even with a perfectly fitting truss rod. No glue will stick to this stuff, but that's okay because you don't want glue sticking to your rod. The teflon tape will cushion the rod in the slot and firm it up very nicely. Costs a few dollars a roll. One roll ought to be good for a dozen or more instruments. Compare that to the cost of the router bit. It's a no-brainer. A few people will most likely be quick to disagree, but believe me, this method will work VERY well.

Good luck with it! You'll be okay.

Mike,
I forgot to add (and so did Todd) that this table saw thing is ultra easy. Center up your cut as best you can, then run the neck over the blade once. Then flip the neck end for end and run it over the blade again. Presto: Now you have a perfectly centered slot that might or MIGHT NOT be of the precise width you want. No worries. It'll be very close to what you want. Now, re-read my previous post about teflon plumber's tape to cushion the rod in the slot. Glue in your top spline over the slot (the top of your rod is cushioned by the tape, too. Then you are good to go. You want enough tape for a snug, press fit. If you do that, it won't rattle.

Cheers!

The problem with the table saw route (route?) is,
his peghead is already on,
so he would have to do some jigging.
I like the tape idea.

I use a 3/16" dia bull nose router bit. (available from MSC and other tool suppliers)
It makes a nice round bottom truss rod slot that will accept the round shaft of the truss rod.
Very slick and pretty much eliminates any chance of truss rod rattle in later life.
Also get some 3/16" pin stripe tape at a good auto paint store and cover the top of the rod with it. Eliminates any glue seeping down into the shaft and compromising the adjustability of the truss rod.

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Hank Mauel

Alan, Unless I've missed something, Mike doesn't state whether his peg head is on, nor whether his peg head face veneer is on. But even if it or they are both on, it's still no problem. If the veneer hasn't been applied, the neck will ride fine on the saw table. If the veneer IS on, he can shim the neck with a couple of temporary glue shims to make it ride level. Yes, in that scenrio the slot would cut through the face veneer of the peghead right up to the nut slot. Still no problem. Mike will widen a space for the truss rod nut. Then he can make a truss rod cover that snugs up to the nut and completely covers the slot. If he's fussy, he can fill that little part of the slot with a shim first. I've done this several times (always before applying the face veneer). I always do it on the table saw. It works fine.

Maybe I'm missing something here,
but, if I were pushing a neck through the tablesaw, with the headstock piece already there,
wouldn't the headstock hit the fence, and stop there?
I would think an angled piece would need to be placed so the fence of the table saw would clear the headstock.

Also, you would have to figure in the slight angle of the fb/neck.
From the top view.
Ack.

Truss rod slots would typically be cut/routed/plowed before the neck blank is tapered and before the headstock ears are glued on. If the ears are already glued on, yes, you'd need to place a spacer strip between the neck and fence to make the ears clear the fence and make the neck track straight on the saw or router table. If the face veneer is on the headstock, then you'd need temporary shims running the length of the neck on the future gluing surface where the fingerboard will be applied to make it track level on the table. If the neck is already tapered, yes, you'd need tapered spacers, and you'd remind yourself to cut or rout the slot earlier in the process on the next neck. If the neck is tapered, shaped, rounded on the back, etc., then it's really a complicated problem, but it's still possible. In fact, over in the "repairs" topic at MIMF, there's a thread about this very problem, and how to jig up for it.

FWIW, cut 4 small squares of craft-store felt & space them equally along the 1/4" slot. Press the trussrod down into the slot (so the felt "envelops" it) & glue your filler strip. You'll be fine.

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Dave
Milton, ON

Cphanna and Dave, i like both of your ideas. I'll have to think for a bit to see if I'll use either one, or just wait until i can get a router bit the proper size.
Regarding the table saw, my headstock is already attached, shaped, and veneered, and the neck dimensioned to size. So I'll avoid that alternative. But it does sound like something to look at for future builds. I'll have to experiment with that until I get it right, but I think that, in the future, i may prefer that method to routing the channel.
You've all given me a lot to think about, and i appreciate everyone's help and opinions.
Todd, the "HELP!" approach sounds like it could be a winner, but I can wait until I can get the router bit. I'll save that option for something I can't get or figure out on my own or with advice on the forum.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.