Compensated Nut Jig and mini pin-router

[kiwigeo]

For the last few weeks Ive been agonizing over jigs and procedures to cut a compensated nut. I tried a jig with adjustable brass blocks and an end mill in a drill press. The thickness of the jig combined with sideways deflection in the drill press gave some poor results.

I ended up making a simpler jig from plastic chopping board along with a purpose built Dremel mini-router. Results were much better and the resultant nut only needed a bit of minor touching up with a bit of sandpaper.

1. The jig everything is held together with double sided tape. Note the nut blank in the jig is a recycled blank from an earlier test run.

2. The mini pin router. The cutter is a 1/8" spiral downcut bit.

[lamanoditrento]

More than one way to skin a cat

[kiwigeo]

A milling machine would be nice but the budget is very tight at present.

[johnparchem]

Very nice jig!

[simso]

Martin, I am a little lost.

First nice jig.

How are you pre determining those points for compensation.

Steve

[kiwigeo]

Martin, I am a little lost.

First nice jig.

How are you pre determining those points for compensation.

Steve

Compensation is calculated using the method from Gore and Gilet.....it involves mathematically modelling the neck of the instrument. There are alternative methods....eg determining compensation on a string jig with moveable nut and saddle.

[simso]

K.

Wasn't someone a little while back experimenting with a jig for tuning the string at both ends so they could physically work out the required nut compensation

Steve

[kiwigeo]

K.

Wasn't someone a little while back experimenting with a jig for tuning the string at both ends so they could physically work out the required nut compensation

Steve

It may have been me. I have this jig set up in the shop at present. I plan to compare values from this method with the mathematically derived values. The jig is basically a dummy fretboard with frets at 1st, 2nd, 5th, 11th and 12th position. You basically set up the string with same action and nut height as on the instrument and then play with saddle position until 12th fret note is exactly twice open string note. You then move nut in a fraction until 1st and 2nd fretted notes are playing in tune. A bit of jiggling involved but it works. I plan to modify the jig so I can dial in neck relief and string run from nut to tuner as well.

[GregL]

Hi Steve,

Perhaps you're thinking of me? I built a jig with adjustable "bridges" at both ends of a neck (ie nut and bridge ends) - also with moveable frets (viewtopic.php?f=24&t=6406&p=72363#p72363). But I'm so slack that I haven't used it yet!

Thanks,
GregL.

[simso]

That is right.

Would love to see the finished item one day. when you were originally discussing that topic, I was also thinking of doing the same (copying you).

The only difference was, I was considering using a removeable template on the jig, the removeable template was a fretted scale length board, so you can switch it out for a 25.5 or 24 and 3/4 and tweak the nut compensation to the string and scale length and then mirror that onto a guitar.

I actually started, I made a steel lap board, so nice and flat out of maple. Never got around to finishing it but

Steve

[GregL]

Hi Steve,

That's why I had moveable frets - so I could set it to any scalelength - from tenor uke to bass guitar (and beyond). (Have a look at the link and you'll see the moveable frets). Your idea of scalelength templates would make it quicker for "standard" scalelengths, though!

Thanks,
GregL.

[simso]

Your system is elegant to say the least.

For me, I have never needed to make a compensated nut on a uke or mando, I am sure one day it will happen.

The only reason I was going a pre fretted board of a scale length, was it allowed me the super accuracy achieved by cnc for fretted positions, nothing more than that.

I would recommend switching out the nut ""bridge"" as you have a rolled edge, something like a floyd rose block would give a clean hard edge for exact placement and marking of the intonation point.

Will have to pull my finger out and finish that project as well, gives me the shits doing it the old fashioned way on a persons guitar,

Steve

[lamanoditrento]

I have been frequently looking at this thread and the jig described in the book and then I've been procrastinating making a pin router jig using either drill press or dremel for a while now. But I have finally figured out a different method

The most accurate machine in the shop is the table router on which the height adjustment is 50 thou per revolution of winder. So I chiselled a relief the size of the nut blank in some scrap wood and marked the string spread. Then the first fence I set the cut to the fretboard height and the second to have the cut over the string, and simply wound up the bit until I got the right height.

I think I will make an adjustable jig to take nut blanks of all sizes, but I pretty happy with the proof of concept and the results which are now as accurate as my callipers allow...

Nut recessed and string spacing set.jpg (88.46 KiB) Viewed 20528 times

Router and fences.jpg (113.58 KiB) Viewed 20528 times

Measuring depth.jpg (82.16 KiB) Viewed 20528 times

Close up.jpg (108.8 KiB) Viewed 20528 times

[colburge]

Good idea Trent, I think I will try it on the next one.

Thanks

Col

[simso]

Be good to see the whole process once your happy with it, from raw to fitted

Steve