Need some help with using the neck-jig....

[Mike Kolb]

I've been staring at my StewMac neck jig in the corner of the shop for about 7years now, never actually needing it, as most fret-level jobs and refrets have gone pretty smoothly ... just lots of dumb luck.  Someone mentioned on a recent discussion that "doing a Les Paul without a neck-jig is like...(fill-in the blank, meaning it's pretty necessary).

So here I sit with a Les Paul on the bench with a thin, floppy neck... in dire need of a really good and accurate fret-dress. My standard procedures aren't cutting this one. Not having a spare Plek machine handy, I'm thinking it's probably time to break-out the neck-jig and make it earn it's keep. I've read all the directions, watched the accompanying video (VHS!) 'til I'm blue in the face, but still don't have a crystal-clear idea of how to put the thing to it's best use. I dropped an e-mail to StewMac for some guidance, but got back a pretty fuzzy response about how the jig is "an indispensable tool that produces accurate neck & fret readings". Umm, I s'pose it does, but...?

See if this sounds about right: you strap the guitar on the jig... strung to pitch with normal relief, you set the metal dowels against the neck and set the dial-indicators to zero. You remove the strings, the neck and dial-indicators go wonky; you strap the neck down and adjust it back until the indicators return to zero. At this point, if you level the frets, aren't you leveling against the existing relief in the neck?  Shouldn't there be zero relief if you want level frets, introducing the relief later?  Never mind the "ramping-down"" above the 14th fret... I just want to get the basics of this beast under control.

It's clear that I'm really missing something here. Anyone who's used and mastered the neck-jig will be my hero if you can explain where I'm dropping the ball.  Thanks.

[Tom Krebs]

The missing piece is that you adjust the neck straight with No Relief at pitch. Remove strings, adjust jig back to straight, and do the fret work.

[Grahame Myers]

Hi Mike
Ya bought something for $ 370.00 and didn't get round to using it for seven years? I must be doing something wrong: It looks like your shop is earning so much money you don't know what to buy next, lol.
It certainly looks like a nice tool though, it's been on my list of things to buy for a while now, along with the jaws fret-press system, a better bandsaw, the binding jig from Stewmac etc, etc.....
Maybe when my new workshop extention is finished in a week or two (after which I'll have, gulp, 70 SQUARE FEET of workshop space, awsome huh? :-) , I can think about buying some new toys to fill the empty spaces on the walls :-)

best
Grahame

[nathan clark]

Hey Mike,

Tom's got it right. I would add two tips.

While the guitar is strung up and strapped into the jig, adjust the peghead jack to fit between the beam and the end of the headstock. Then remove strings and simulate the nut-strap's downward pressure with the palm of your hand and observe the dial indicators. Adjust the peghead jack a little if need be so your hand pressure gets the indicators to read zero. Now apply the nut-strap and tighten until the dial indicators both read zero. You might need to make some more minor tweaks.

Use a sanding bar/beam that's longer than the fretboard. Use self-adhesive sandpaper on the sanding bar.

Have fun.

[Paul Breen]

I have not found it necessary to tune the guitar to pitch or for that matter have the strings on at all to strap it in. All that matters is that you are holding the neck (frets) in a flat plane. I get the same results either way so I don't bother with the strings under tension any more. It is important though to first assess the working range of the truss rod before anything else. If the truss rod is loosened up under full string tension and you can't quite get enough relief, then the neck can be positioned in the jig at a slight back bow. This allows you to take a bit more off of the frets where you need the relief. I built my own jig and don't bother with dial indicators either, a good straight edge is adequate.

[nathan clark]

If you don't put the guitar in the jig tuned to pitch and zero the dial indicators, than you're approximately simulating string tension. Seems like it wouldn't take much longer to simulate string tension if your jig has the dial indicators...

[Paul Breen]

Nathan, flat is flat whether I arrive at it with string tension or not. I get the same results either way, try it sometime. Like I said, a good straight edge is just as good as a dial indicator. I use it in conjunction with feeler gauges, just as accurate and a different way to the same end.

[Pierre-Antoine Roiron]

Paul, I do roughly the same for my refrets or redress jobs. But sometimes, I use a jig (homemade stewmac style) because on some necks, the deformed shape is more of a S shape (old fenders mostly) an you have to plane it under tension.

[nathan clark]

Paul,

I don't mean to be confrontational. I guess I don't fully comprehend your approach. As we both know, when a guitar comes into the shop needing fretwork, the neck is almost never "flat", no matter how the truss rod is adjusted. That means, the neck needs to be adjusted to reach a compromise between the tension you want to see on the rod, any distortions in the fretboard/frets and the geometry of the guitar. That said, how do you map out twists, etc...with a straightedge so you can recreate them without strings? Do you measure the gap between the straight-edge and a specific fret with a feeler guage, or something to that effect?

[Paul Breen]

Pierre, once the guitar is strapped in and the strings removed the tension is gone. All you are doing is making the neck follow the contour of the rods, it is not under any tension at this point. If it is deformed like an S or the like I determine if a leveling will deal reasonably or not with the amount that it is out. Only a slight amount of this deformation will qualify for a fret leveling. If I think I have to level off too much fret I will recommend a re-fret so I can deal with the underlying issue, the finger board.

Nathan,

That said, how do you map out twists, etc...with a straightedge so you can recreate them without strings? Do you measure the gap between the straight-edge and a specific fret with a feeler gauge, or something to that effect?

I guess I don't follow your reasoning. How do I map out twists, est. so I can recreate them??? I am trying to get ride of them, I don't want to recreate them. Yes, I use a straight edge with feeler gauges and back light the neck by shining light on a vertical White panel behind the work. You can see the lay of the land quite easily this way. A good straight edge is necessary to evaluate the entire finger board. The dial indicators will tell you nothing about your finger board extension. Example, If I lay a straight edge on a fingerboard that spans from the first to the 12th fret and can adjust the truss rod to make 1 - 12 flat enough to level but then check it again with a straight edge that will span from the first to the last fret and find it is only touching the first and last frets, I know I have a rising finger board extension that must be dealt with first.

It is completely necessary to read the neck with the strings on and up to pitch but I have tried both ways and found no advantage to strapping them down on the jig with strings up to pitch. If the frets are that bad they are coming out and the finger board will be dressed to correct issues that require removing too much fret material.

[nathan clark]

Hey Paul,

We are totally having a misunderstanding here. I think I'm making too many assumptions about the not-described details of your working methods and you seem to be doing the same. To help clear things up, I'm going to briefly explain my process step by step. If you're not sick of this thread already, maybe you could do the same?

I start a fret leveling or fingerboard leveling by adjusting the truss rod to make the neck "straight" (while it's strung up and tuned to pitch), which means reaching a compromise between the tension I want to see on the truss-rod, any distortions in the fretboard/frets and the geometry of the guitar, etc... Essentially, I'm coming up with a game plan for how I am going to sand the frets/fretboard straight: I'm mapping the fretboard to decide where I can and where I can't remove material, then adjusting the truss rod accordingly.

While the guitar is strung up, I strap it into the neck jig, zero the 2 dial indicators (which are touching the back of the neck) and take the strings off. I then force the neck back into the position it was in under string tension while in the jig. This is the purpose of the dial indicators, they tell me when I am accurately simulating string tension. Simulating string tension accurately re-creates the twists, humps, etc... so I can sand them away<./i> While under simulated string tension, the fretboard tongue/extension is positioned just as it was when it was under actual string tension.

With the guitar under simulated string tension and the neck supported by the metal rods, I sand the fretboard/frets so they are level and appropriately radiused. Because all of the twists, humps, etc are present when simulating string tension, I can quickly and easily correct them by sanding away the high spots.

To be clear, the Erlewine neck jig doesn't help with diagnosing the neck, I still need to understand what the neck, frets and fretboard are doing and how to correct the guitar without giving the neck too much/little relief, without changing the neck angle and without sanding any frets (or part of the fretboard) too low/thin. The neck jig simply allows me to simulate string tension so I can freely sand the neck/frets without the strings in the way.

Make sense?

[Paul Breen]

Nathan, I understand your take on this.

True, the initial flatness of the frets than can be achieved in the jig is a compromise of a number of possible issues. You won't be starting out all nice and flat, that is why it is getting a leveling in the first place. I just don't agree that setting the jig up with the instrument under tension has any advantage over setting the jig up without strings on the guitar. After assessing what and where I need to remove material I just put the rods where I need them, assisted with my straight edge, to achieve that end. When the strings come off with your method there is no more string tension at that point, you are just forcing the neck to go where you want it by strapping it in place. Don't you see we are really doing the same thing?

[nathan clark]

Paul,

Please correct me if I do not understand you.

While the guitar is tuned to pitch, you observe where you need to remove material from the frets/fretboard.

You put the guitar into your jig.

Your jig uses rods beneath the shaft of the neck to force the neck into simulated string tension.

You level the frets.


Okay, I definitely understand that there's more than one way to skin a cat. So don't get me wrong when I say that this is not how the Erlewine neck jig works. The Erlewine neck jig simulates string tension by:

Pushing the very end of the headstock up with a turnbuckle device and pulling down the nut portion of the headstock with a strap. These two forces simulate string tension. The 2 dial indicators simply let you know when you've put the neck under the proper amount of simulated string tension. The metal rods are designed to prevent the neck from deflecting as you level the frets.

I want to understand the parallels and differences between our working methods. So my questions are:

How, specifically, are you ensuring that the neck appears in your jig without strings as it appeared under string tension? Are you using your straight-edge and feeler gauges to this end?

How many rods do you have pushing up against the back of the neck? Where are they located in relation to the neck/body joint and nut on, say, a les paul?