Too much forward bow

[neepheid]

One of my basses had too much forward bow and I couldn't tighten the truss rod nut any more for fear of breaking it. At first I thought it was maxed out, but after some measuring of the threaded part of the truss rod and the depth of the truss rod nut I worked out that it couldn't be the case. I was simply asking too much of the truss rod to move the neck to where I want. So after a bit of googling I found this advice:



Basically, tighten up the truss rod as far as you dare (this pulled it just about straight on my neck even with no string tension), then clamp it as shown and tighten that clamp until at the desired position then tighten the truss rod again to this new position. I am pleased to report that it worked, and worked so well that I actually had to loosen by a quarter turn once the string tension was applied. I'll admit it was total guesswork - I clamped the neck into a slight back bow because I figured the strings would pull it right and they pulled it straight, ready for me to dial in a little relief by loosening a quarter turn or so.

I left it overnight and it's looking good. Relieved to have a much nicer playing bass with action more like what I'm used to without the high fret buzz

[discreet]

Fantastic work. I couldn't do it though, I'd never get to sleep with the worry.

[BassBus]

Yes, I have done this. Wood is very flexible so will take quite a bend without any problem. Think of the sides of an acoustic guitar.

[Twincam]

A slight word of caution with this method, use softer wood blocks top and bottom to avoid marking the bass. And never put the top blocks against the frets as the side ways force can disturb them, so in between the frets or spread the load on top over a few frets, same with the nut as in the illustration you can actually tear off a nut like that as the force is sometimes high depending of course how much you put in some necks need more than others.

You can do a similar reverse method to bow a neck if required too, needs caution though!

[pfretrock]

i've been lucky and all my basses have responded immediately to small truss rod adjustments - except an Epiphone, which moves overnight after adjustment. I've heard it advovocated that after a small adjustment you grip the body (between your knees, I think) and push the neck in the desired direction. I think the general idea is the truss rod may not have enough force to move the neck, but once moved, it holds it there. Always a good idea to check next day before making a second adjustment (the Epi told me that!). Cork sanding blocks may make good block for the OP's method. I can see the merit in this method as you can apply a small controlled force from the clamp

[neepheid]

This truss rod was totally unable to move the neck even with no string tension applied, it had all the symptoms of being maxed out - couldn't turn the nut any further for fear of stripping threads/breaking the rod.

FWIW, I used whatever wood blocks I had to hand but put cloth as padding between them and the neck. Cork sounds ideal though, good shout. I thought protecting the neck would have been obvious, but I guess it's good to mention it.

Also, I don't think this will work for dialling out back bow if you have a one way truss rod. Without the application of heat - the wood will just spring back to its original position unless you have the counteraction of a two way truss rod to fix the change against.

Pleased to report that after a day of settling the neck is looking good, relief is staying constant.

[Grangur]

Just discovered this thread. I've got this issue on a bass.

Thanks guys for the info.

[Marc S]

Luckily for me, I've never had this issue with a bass. But that's a useful technique, and it's simple too - thanks for sharing it

As has been said though, this must be done with some caution. I'd be concerned about making too much adjustment in one go, and I think I'd prefer to do just a small amount of tightening, then leave it for a few hours, or overnight before making another small adjustment. Did you tighten the tension on the G-clamp a lot in just one go? Or did you do several, gradual adjustments?

[Grangur]

The bass I'm working on is an expensive Warwick with a through neck. When I bought it, the action was high, lots of relief and the frets were tarnished.

After removing the strings I polished the frets, replaced the strings and did a set up. I found I can get the action at the 24th fret down to 2mm and it feels better. With the truss rod it seems to max out with the action at the 9th fret being a touch over 1mm. I like it a bit lower than that.

I received this bass this week, with strings up to tension and the TR was loose. I my guess is the bow is due to poor maintenance.

So last evening I fitted the clamp as in the OP. This can not go wrong. There's no option of replacing the neck. So I applied the clamp to the neck to the point where it was all simply held in place, then applied another 1/2 turn. This allowed me to get another bit of a turn on the TR tool.

Left over night and this morning I was able to get a bit more of a turn on the TR. Left it clamped again all day and tonight I checked it out with strings: Not much different to how it was not the beginning.

So, back on with the clamp. I wish now I'd measured it more accurately, but think I could be in for a long haul here.

If anyone here has ant experience of this they can share, I'd really appreciate your comments.

[Manton Customs]

On 10/11/2017 at 19:05, Grangur said:

The bass I'm working on is an expensive Warwick with a through neck. When I bought it, the action was high, lots of relief and the frets were tarnished.

After removing the strings I polished the frets, replaced the strings and did a set up. I found I can get the action at the 24th fret down to 2mm and it feels better. With the truss rod it seems to max out with the action at the 9th fret being a touch over 1mm. I like it a bit lower than that.

I received this bass this week, with strings up to tension and the TR was loose. I my guess is the bow is due to poor maintenance.

So last evening I fitted the clamp as in the OP. This can not go wrong. There's no option of replacing the neck. So I applied the clamp to the neck to the point where it was all simply held in place, then applied another 1/2 turn. This allowed me to get another bit of a turn on the TR tool.

Left over night and this morning I was able to get a bit more of a turn on the TR. Left it clamped again all day and tonight I checked it out with strings: Not much different to how it was not the beginning.

So, back on with the clamp. I wish now I'd measured it more accurately, but think I could be in for a long haul here.

If anyone here has ant experience of this they can share, I'd really appreciate your comments.

There's a few options you can look into. Starting with the least risky, you could try doing similar to what you're already doing, just give it longer in the clamps (a week or two) to let the wood gradually bend. If you can gradually clamp it into a backbow so much the better, there will always be a certain amount of "spring back" when the clamp is removed. Did you remove the truss rod nut (if it's that type of rod) before clamping? Here's a video of the basic procedure the OP is describing. But you'll notice the truss rod nut is removed.

 

You could also try the same basic method, but leave it somewhere a bit damper, the damper atmosphere should make the wood move/bend easier. Once you've got it where you want it, bring up to normal temperature/humidity still in the clamps.

A (more risky) option would be to use heat while clamping, see this thread for more info https://www.talkbass.com/threads/rescuing-a-badly-twisted-1964-jazz-bass-neck.1137165/ which is mainly referring to a twisted neck, but the basic idea is the same.

The last option is to get it as flat as you can, then pull the frets, level the board and refret. How viable that option is depends on how much bow is present.

Whatever you do, don't force anything too hard and make sure you're applying even pressure, otherwise you can end up with a twisted neck.

 

 

Edited November 12, 2017 by Manton Customs

[Grangur]

Hi @Manton Customs very many thanks for your post. It's late now and I'm in bed. Tomorrow I'll put it in the garden shed. I'll leave it a few days and see what happens. I'll take some pictures and measurements too. 

When putting it in the clamps i was adjusting the truss rod to get it right. What I found interesting was when under no tension the TR squeaks as I turn it. When under tension it , again squeaks. Yet the was/is a time when it's under a small degree of clamp tension, that it turns quite freely. I guess that is the point of bend that I need to get it to be at it's relaxed state.

[Manton Customs]

You might want to try again with the truss rod nut undone (if it has one), use the clamp to get a slight backbow if you can. Then tighten the truss rod nut once you are happy with the relief.

Keep an eye on it if you put it in your shed, for a shortish period you should be fine and the damper atmosphere may well help, but don't subject the bass to anything too drastic.

Good luck!

[Grangur]

As the bass is a Warwick, the truss rod adjustment is in a cavity in the headstock. The truss rod is a 2-way device.  I've "undone" the Truss rod to the point where it has started to increase the relief and get tight again.

So when clamping I've turned it to what seems to be a neutral position. Then applied the clamp and then tightened the TR. Tightened the clamp some more and given the rod another tweak. Then added another small turn to the clamp. 

Right now the bass is clamped and in the garden shed. The space differential between the ends and the centre is about 6mm. So the curvature is appreciable but not nerve shattering.

[Grangur]

Home now and able to take a better look at the bass.

Having measured the gaps again, it seems the neck is currently bowed by 3.5 - 4mm. Not as much as Dave bends his in this film at 5.50mins.

So I've given the neck another small twist to the clamp. I'm dreading hearing a creak of the wood splitting.

[Grangur]

Right, had her back indoors again. Eased off the truss rod completely, turned the screw on the clamp some more and did the TR back up again.

Reason for doing this is I was concerned that I might not have enough of a curve going on and didn't want to have the clamp rip the TR.

Probably best to leave it now for the rest of the week. Back outside now.

[gary mac]

Hope this has a happy ending Rich.

[Grangur]

Hey @gary mac many thanks. Hope you're well.

I'm sure it'll be fine as long as I take it slow.