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| Rear truss rod routing? http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10123&t=46180 |
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| Author: | abarson [ Fri Aug 14, 2015 5:50 pm ] |
| Post subject: | Rear truss rod routing? |
I recently got a birdseye maple Jazz neck blank. The headstock received a slight "kiss" while the bandsaw was cutting out the rough shape, which I can live with. It is currently exactly 1" thick. I initially was going to cut it down to 3/4" and use a cocobola fretboard, but it's just to dang pretty! I'm now really interested in making this a one-piece neck. Questions: Can I use a straight 2-way truss rod inserted in a channel carved from the back, or must it be a one-way curved rod? Why? Can someone provide some guidance/measurements for correctly cutting the truss rod channel? Is there any structural reason for the skunk stripe to be non-maple? I'm still debating the aesthetics of using something dark like walnut, but want to be sure it won't be compromised. Would something like purpleheart prevent the truss rod from operating correctly? With the headstock already cut and at a uniform 1" thickness, is there a way to cut it so that it would be angled instead of flat? I'm not talking about a scarf, but rather removing material on the front and back to make it angled. Any concerns with adjustment nut location with this arrangement? |
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| Author: | Rodger Knox [ Mon Aug 17, 2015 1:22 pm ] |
| Post subject: | Re: Rear truss rod routing? |
No, you shouldn't use a straight 2 way rod inserted from the back because a 2 way rod works by curving when it's adjusted, and taking the neck with it. All the force would be on the glue joint of the cover strip (skunk stripe), or the cover strip itself. Correctly cutting the channel depends on the truss rod, and which end has the adjustment. Any hardwood would be OK for the stripe, there's no structural reason for it to be non-maple. I don't think 1" thickness is enough to get an angled headstock with enough break angle over the nut. We need a little more information(type of truss rod, adjustment location) to give more detailed directions. |
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| Author: | JimO [ Wed Aug 19, 2015 10:45 am ] |
| Post subject: | Re: Rear truss rod routing? |
The way StingRay basses are made. They cut off the fretboard, route out for the truss rod, install it, and glue the fretboard back on. You can't tell it was ever removed. Looks like a one piece neck. https://www.youtube.com/watch?v=Q_oXBvr8AhU |
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| Author: | abarson [ Sat Aug 22, 2015 11:12 am ] |
| Post subject: | Re: Rear truss rod routing? |
JimO, That was my original thought, but with the blank currently at exactly 1" thickness I think it would end up too thin, compensating for the saw kerf removing material. If that isn't a concern, it would probably be the easiest solution. Roger, So are you saying that if it is back mounted it has to be a curved slot with a single action truss rod? I also came across a thread on a different forum where the builder used a dovetail bit for the slot and inserted a trapezoid to prevent the lifting you mentioned. Looks cool, but may be beyond my skill level. |
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| Author: | Rodger Knox [ Thu Aug 27, 2015 4:43 pm ] |
| Post subject: | Re: Rear truss rod routing? |
abarson wrote: Rodger, So are you saying that if it is back mounted it has to be a curved slot with a single action truss rod? I also came across a thread on a different forum where the builder used a dovetail bit for the slot and inserted a trapezoid to prevent the lifting you mentioned. Looks cool, but may be beyond my skill level. There are ways it can be done, but you need to understand the forces that make it work. Tightening a single action rod puts the rod in tension, and that offsets the tension of the strings. The further the rod is from the neutral axis, the less tension it needs to offset the strings, so closer to the back of the neck is better, and routing from the back makes sense. The rod does not exert any force on the cover strip, so it can be thin. Tightening a double action rod makes it curve, so the ends of the rod are pushing toward the back of the neck, and the middle is pushing toward the fretboard. The wood (or glue joint) at the ends of the rod needs to be able to withstand that force. The distance from the neutral axis makes no difference, so further from the back of the neck is better, there's more material to resist the force. 1/8" is absolute minimum, and that might not be enough depending on the strength of the neck wood. |
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| Author: | abarson [ Fri Aug 28, 2015 6:31 pm ] |
| Post subject: | Re: Rear truss rod routing? |
Now that is an explanation that makes total sense. Thank you! So does anyone have tips on rear routing a Jazz bass neck for a single action truss rod? Checking Allparts, they have different anchors with different adjustment nuts. Will either work in this application? https://www.allparts.com/LT-8023-000-Si ... _4597.html https://www.allparts.com/LT-1420-000-Si ... _2148.html |
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