Working through replacing a truss rod in a Jazz bass neck

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joppo
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Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Tue Dec 01, 2015 10:18 pm

I'm doing a repair on a friends Jazz bass neck, and though some of you might be interested in seeing it in progress.

The story is a friend has acquired a 20 year old Squier Jazz Bass. It is nothing flash, but is in reasonable condition except for the neck being bent like a banana and the truss rod is broken from trying to straighten it. It probably isn't worth the effort, but we decided to have a go at replacing the truss rod (it was either that or throw the whole thing out).

I started on fixing it before I thought about doing this post, so I've 'engineered some photos to show what I've done so far, and I'll post some more pics as I progress. The first photo is the neck removed from the bass. Even with no tension on the broken truss rod, there is a distinct bend in the neck.
Banana.jpg

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Tue Dec 01, 2015 10:26 pm

The first job is to carefully remove the fretboard. I drilled three small holes on each side in the heel of the neck. The holes are right on the joint line between the rosewood fingerboard and maple neck. You can just see them in this photo (the fretboard has already been removed in this photo, so just holding the fretboad on the rest of the neck here so you get the idea). These holes give somewhere to start gently levering up the fretboard.
drillings.jpg

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Tue Dec 01, 2015 10:36 pm

The hard part is getting a blade started between fretboard and neck. There are special little trowels for the job, but I used my home handyman puttie knife. It had a reasonable edge without being too sharp. I forced the blade into each of the small holes I had drilled, being very careful to stay right on the join. The glue starts to give slowly, and after about 5-10 minutes of careful work, I had the blade deep enough to work my way slowly up the neck. I had another putty knife on the other side to balance up the force, and I worked my way up from the heel to the headstock which took about 25 minutes of slow careful work.
scrapper.jpg

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Tue Dec 01, 2015 10:46 pm

So here is the neck and fretboard separated. It worked really well, with just a small amount of rosewood left at the heal where I started.

Unfortunately, I didn't take a photo when I removed the neck. In this photo, you can see the old truss rod. This neck had a single action truss rod that was put into the neck from the other side. All I could see was the top and tail of the truss rod. The rest of it was buried under a fair bit of maple. I painstakingly dug it out from this side using a chisel. The rod was close to the surface you can see at the top and tail, but was around 6-8 mm deep in the middle. It probably took an hour to chisel away enough wood to expose the truss rod, and then I was able to pull the old rod out of the slot.
fretboard off.jpg

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Tue Dec 01, 2015 10:53 pm

Another view of the slot with the old truss rod removed and placed to the right. I need to fill this slot with a piece of maple to make sure the neck is back to full strength (i.e. no gaps inside the neck) before routing the slot for the new truss rod. I can't use the old slot because it is variable in depth and I'm using a different type of truss rod.
rod removed.jpg

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Tue Dec 01, 2015 10:56 pm

Here I have removed the tuning machines and clamped the neck onto a straight piece of wood. I'll leave it like this for a week to try to remove any bend and twist in the neck while I wait for the new truss rod to arrive. Sitting like this, there is a very slight reverse bend in the neck, so it will do it good to be bent in that direction for a while.
clamped.jpg

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by john » Wed Dec 02, 2015 7:06 pm

Wow, what a brave undertaking. I love this sort of thing
If the neck (wood) is twisted from the grain do you think there is a chance it might re-twist when the clamps are removed?

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Wed Dec 02, 2015 7:13 pm

Yes, it probably will retwist, but it is very minor. I didn't notice it when the neck was in one piece. If it was my neck, I would add a carbon rod on each side to strengthen the neck and reduce bend and twist, but that would add a bit too much cost to the repair. The neck is really quite a bit thinner than my Squier VM Jazz, so I guess it was built that way to reduce the wood cost.

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Tue Dec 08, 2015 6:16 pm

I needed to fill the old slot before routing the new one. I got a length of maple to glue in, and measured the depth of the slot. The old rod was deepest in the middle and shallow at each end, so you can see I have shaped the bottom edge (measured every 5cm) so that it will fit nicely.
insert.jpg

Building basses and guitars is all about the clamps! The maple insert is glued and clamped into place.
insert clamped.jpg

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Fri Dec 11, 2015 7:09 am

With the old slot filled, I routed the new slot. The ironic part is that I removed most of the wood I added. Because the neck has quite a bow and is so light, I went for a really strong truss rod. It is 12mm wide by 9.5mm deep and is made of U-shape aluminium. This is a pretty normal depth, but almost 3 times wider than a normal truss rod. This will either be a great success or spectacular failure as a Jazz neck it pretty small near the headstock, and there may not be enough wood there to take the pressure when I apply tension - we just have to wait and see! :shock:

Here I have clamped the neck to get it as straight as possible, and I have glued the new truss rod in with an epoxy glue (good old Araldite), and clamped to get really good contact the whole way along the slot
gluedtruss.jpg

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Sat Dec 12, 2015 10:46 am

Big day today - the fretboard goes back on.

First thing is a little trick to make sure the fretboard stay in the right place while the glue dries. I drilled two small holes part way through the neck, one at each end, and hammered in a small nail. I cut back the nail so just a small piece protrudes with a sharp edge. You can just see it in the photo to the right and slightly under the centre of the picture. I got the fretboard positioned in the right place and then pressed down to make a mark of the back of the fretboard. I drilled a little hole deep enough for the exposed bit of nail to sit in. Now it will only sit in one place and not move when I glue it.
pin.jpg

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Sat Dec 12, 2015 10:53 am

I ran some masking tape over the truss rod slot before gluing so that I don't get a lot of glue squeeze out in the slot.
tape.jpg
The glue is applied, and now I just need to take off the tape and put the fretboard on.
glue.jpg

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Sat Dec 12, 2015 10:56 am

Fretboard is on! :D I have two radiused sanding blocks that just fit the neck, and again heaps of clamps to hold it together. The fretboard is sitting rock solid on the two pins I put in. Will leave it 24 hours before I remove the clamps
fret-on.jpg

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by john » Sun Dec 13, 2015 8:36 am

Great work, Nev. 24 hours is almost up :)

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Re: Working through replacing a truss rod in a Jazz bass neck

Post by joppo » Sun Dec 13, 2015 11:31 am

Clamps are off and a little tension applied to the new truss rod. Feels really solid, and no cracking sounds :D Phew! It needs a little finishing (varnishing) to make it look nice, but I think that is a win!

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