I've had some good results using heat to correct excessive set relief in composite necks by clamping and heating. However, I have a problem one piece maple Fender P neck (c. 1980 and very chunky) with some serious set. The amount of warp and proximity of the truss rod to the top of the fingerboard doesn't allow me to be able to plane the bow out. I should say at this stage that the major deflection is between the 12th fret and the heel. Adjusting the truss rod works a treat at the head end only - resulting in a lovely "S" neck profile :).
Have any of you had much success in straightening a one piece neck of this kind using heat and clamps and if so, do you have any nuggets of advice?
In the absence of a response, I have had a bit to do with two piece bass necks and find them a real challenge to recover well even with some advance carbon fibre reinforcement techniques - the problem with a one piece neck (and I am not familiar with this sort of "one piece" Fender bass neck) is beyond my level.
How do you know the truss rod is too close for comfort - and when you say warped - how much?
If the warp is such that it cannot be machined flat and the truss rod action causes a "compression" S I would have to say a new neck or machine off the existing board surface, install poltruded carbon fiber bar stock and put on a new compression fretted fingerboard. Something like that. Anybody else?
(Just to make sure I'm getting your information right). Do you mean the location of the trussrod (and access hole) are awfull close to the top of the fingerboard?
I had a similar '80 strat neck not so long ago, with a whooping amount of relief, some warp and with very little room to level the board (due to the location of the trussrod at the nut end, and big rising tongue). The neck wouldn't adjust straight/ backbow with the strings off.
In this case I took the frets out, adjusted the neck as favorable as possible (leveled the board end to end, no string tension). And then used compression fretting to stiffen up the neck.
I think heat would have little effect on the neck (if its warped and if there's lots of relief). Of course clamping and then adjusting the neck is allways helpfull.
Russell, Jelle thanks for your help. I'm sorry, I didn't explain very well.
Firstly, I should say that the customer wants a fretless conversion so compression fretting isn't a solution. The neck only kicks up at the heel end by about 0.015" and with the rod completely slack, everything between the nut and 13th fret is pretty straight (enough to work with).
Adjusting the truss rod has the correct effect (majority movement at the nut end, less movement the closer you get to the heel) which results in an overall rollercoaster neck. By my calculations, the solution would be to take down the heel end by around 0.015" but there's the rub. The location of the truss rod at the heel is around 0.100" below the existing fingerboard level so taking off enough to straighten the neck is leaving only 0.085" hence my consideration of using heat to impose an adjustment around the 12th - 13th fret and therefore taking less timber away.
You can see the kick up pretty clearly in this picture and how close the rod is to the top of the neck.
OK having cleared that up, I've had a rethink and I reckon taking off 0.015" would be OK because as I understand it, an adjusted rod exerts pressure down (away from the fingerboard) at the rod ends so a thinner truss rod covering there wouldn't be an issue.
It took me a while to understand what you mean Dave but the last pic brought it home for me.
So we see the infamous ski-ramp in the extension area that is pretty common on Fender style bolt-on necks. Your extension is approx .015" proud of the fret plane represented by say the first though the 12th.
If this is the case the fix is possibly a refret where you level half and only half of the proudness from the extension sands frets which would still leave wood in the truss rod access hole top. The other half since you also ideally want fall-away too can be milled off the tops of the frets after the 12th to the last fret.
I think that you said that this is a fretless conversion. If that's the case the only answer that I see is to level the board and I still think that there is enough material on the top of the access hole to not be a problem. To gain .005" of fall away after the 12th all you have to mill off the extension is .020".
I'm not fond of heat treatments and personally don't think that they are often a lasting fix if they work at all. Ski ramps on Fender style necks on the extension are very common and this is also how we deal with them in a fret dress, level 1 through 12 and then induce fall-away with leveling 12 to last. I like to see about .015" of fall-away at the last fret. It's the same for a fretless, same idea, just no frets and it's the board's surface where the accuracy needs to be.
If the neck is all over the place and you are converting it to fretless consider compression fretting like what we do on Martins pre-truss rod days. Although you are not fretting the neck you will be inserting material to fill the slots. Judicious selection of the thickness of the fret filling material while stringing it up and placing it under full tension and observing where you need more back pressure, more forward pressure, where you need no change and permit you to reshape this neck in the conversion process.
It sounds harder than it is. Typically I place only four frets spaced out fairly evenly and then string and observe. Again let's substitute filler material for frets here for our sake of discussion. When I observe I can see where I may want to move the neck forward or back, write it down such as back at 9 etc. and then do four more frets/filler strips. Restring and observe again.
It all starts with a level board though and fall-away induced to the extension.
Compression fretting sadly will not impact the extension, too much material there so milling down the ski ramp would be my approach and I would use leveling beams as well with 80 grit. After nixing the ski-ramp you likely will need to deepen some of the slots in that area as well if you were using frets, in this case with filler strips you can skip this step.
Ok, that's a different story indeed (thanks for the photo's and measurements).
It wouldn't be my first thought to use heat for this one piece neck (because of the heat needed, and the finish of the neck thats involved), but who knows. Please let me know what the heat does for you (and how you are applying the heat), maybe you'll gain a little there.
Also after removing the frets/and removing/ leveling the finish (fingerboard) you might gain a little
Then there's to deal with whatever is left relief/ hump wise.
I wouldn't just take off 0.015" at the heel end, level it out end to end
Also keep in mind, when you're converting to fretless there's still compression issues that have to be dealt with (which depends on whatever you are planning to use to fill the fret slots with, make sure you don't further weaken the neck)
This is totally out of my areas of experience, but could you use the equivalent of Martin bar frets to achieve the compression fretting? The frets could be leveled to the fingerboard, and used as markers, like many of the fretless banjos had.
"I'm not 100% against such, but it would not achieve much in a case like this, as there's no fingerboard to slip."
I agree 100% with that statement. Plus add a couple hundred pound of pressure on it and...you get the picture.
If a replacement neck is out of the question, I see that you have no other option but to follow Hesh's advice and plane (level) the FB. This is a very common issue with Fender Bass necks.
BTW: if you have at least a name for your shop, you should apply for dealer accounts with CE Distribution and WD Products. Both are great supporters of the independent shop keeper. WD also has some very nice F-Bass necks made in Eastern Europe (where some of the finest orchestral stringed instruments in the world are made). Their wholesale prices are surprisingly reasonable and offer the luthier an opportunity to make a very fair profit while still surprising the customer with a bill that's much less than anticipated.
To expand on the task at hand, I've had success doing fretless conversions by pulling the frets and giving the FB a sanding to remove the factory lacquer buildup around the frets. Then with the truss rod completely relaxed AND the neck supported in it's entire length by a cradle (to prevent the neck from bowing during the next step) glue-in HARDWOOD filler strips* with either CA or Original Titebond, to fill the fret slots BEFORE re-machining the FB. This will eliminate any compression issues when you get to the next step.
Once the glue has cured overnight, you're ready to level the FB. I'd start by eliminating the ski ramp first, true the entire FB per S.O.P. and perform the fall away task per Hesh's direction. One thing you can do at this point to impress your customer (or yourself if this is your bass) is to customize the FB to a flatter profile..if desired. You could also round over the FB edges to give it a played-in feel.
You should now have a fully adjustable neck ready for finish on the top of the FB.
I use CA to finish fretless FB's. It' provides a great feeling finished surface for the bassist AND it's much more durable than and compatible with, lac (on the back of the neck). It is also easy to do touch-ups if required in the future. Dan E. did a great tutorial on this very process...and that's from where I got my info. I recall that it's available on line in Stew-Mac's Trade Secrets section.
Let the finish cure for a few days, tighten the truss rod to adjust the unsupported neck into a perfectly straight geometry smooth out & polish the FB to the desired sheen and you're ready to reinstall, do a setup and you're done. The (or any) amount of relief desired by the player can be dialed in or out later. You should have a perfectly functioning truss rod** and neck at this point.
I hope some of this info (some; admittedly redundant for emphasis) is helpful. Best of luck with the conversion and post-op pics will be enjoyed by all :)
* your fret slots can be widened a bit to accommodate thicker filler strips. At this point, they're only cosmetic and fretless bassists are used to no markers at all, only side dots.
** Truss rods only affect the FB starting at the 4th-5th frets to about the 10th fret. Problems like the instant case can only be corrected with the described 're-engineering'.