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Neck and Bridge locating jig

Posted: Sun Sep 20, 2009 8:48 am
by Craig
Here's a jig I made up a few years ago that does three things:

Fitting the neck to true centre

Positioning the bridge square and to any given string length

For saddle/ string alignment to fretboard


Establish the string length of your instrument and adjust the nut end of the jig to suit ( this part sits in the nut slot )


Make marks dead centre on your fretboard at the nut and heel ends and lay the jig on top so that it's scribed centre line corresponds . Adjust the side positioner wingnuts to suit . These will adjust to suit the taper of the fretboard.

As the jig has now been adjusted to suit your instrument , you can take it on and off as required. From here you can fit/floss the heel to centre the neck to the body of the intrument ( aligning it to a centre mark at the bridge position )


The little strip of Mahogany attached to the jig fits in the saddle slot of the bridge ( I have mine set at a 3 degree angle ) thereby locating the string length and also centers the saddle to the fretboard .


I have 1/16" locating holes at each end of this little strip . Place the bridge in position with the mahogany strip in the saddle slot and drill through the bridge and soundboard. You can now remove the jig and glue on the bridge using little brads or whatever as locating pins until the glue dries

A parcel of sheep dags to anyone who can come up with a name for the jig ! :D

Posted: Sun Sep 20, 2009 10:57 am
by Mark McLean
Having just done a neck alignment and reset in the last week I can instantly see how much easier it would have been with one of these jigs. And bridge placement in a snap also - that is a very nifty device!
I've got a couple of questions:
1. How did you mark or etch the centre line on the perspex?
2. You must use something to square the nut-end piece with the centre line. Do you take square off the edge or the centreline. Could you scribe some permanent right-angle lines at the usual scale lengths?
3. Is the perspex rigid enough to use in estimating neck angle and bridge height? If it was a reliable extrapolation of the line of the fingerboard you could measure height to the fingerboard at the saddle end. Do you do that, or is it too flexible?

Fantastic jig - thanks for sharing it.

Posted: Sun Sep 20, 2009 2:57 pm
by Craig
G'day Mark,

To answer your questions:

(1) I used a straight edge and steel scribe to etch the centre line . It shows up well . Better to etch the surface that contacts the fretboard

(2)The adjustable nut insert part finds 'square' by setting it while it's in the nut slot resting against the end of the fretboard (which should be at 90 degree to the fretboard in the first place ) .
Scribing marks at the nut end for differing scales is a good idea . I have done this for two that I use

(3) the acrylic is too flexible on it's flat , to give an accurate reading above the bridge to establish your neck rake Mark . I've thought of adding stiffening bars etc. but it really isn't too much hassle slipping it off . That measurement above the bridge is fairly important to the final set-up of the guitar, and I'm only really happy using a " proper" straight edge to get a reliable reading . Maybe a thicker Lexon would flex less, but would bet there would still be some flex.

Posted: Sun Sep 20, 2009 5:24 pm
by Dominic
Neat idea Craig. I had been contemplating making one of those self centring jigs but your idea is simpler and easier with the adjustable things on the side. And I like the saddle slot alignment thing as well.

What if I had two adjustable pins instead of a bar? That way I could fit it to different slot angles if I screw up and the slot is off a bit.


Posted: Sun Sep 20, 2009 6:51 pm
by jeffhigh
yah shoulda sold it to (CF) Martin back in the 70's when they needed it

Posted: Sun Sep 20, 2009 9:27 pm
by Craig
Dominic wrote:

What if I had two adjustable pins instead of a bar? That way I could fit it to different slot angles if I screw up and the slot is off a bit.

Hi Dom. Two pins in the saddle slot instead of my Mahogany strip should work O.K. ,but you'd need to have them positioned so they enter the very ends of the bridge's saddle slot to have the alignment(s) correct.

Can't remember much of the 70's Jeff . It's all a bit of a blur, :? but I doubt locating jigs were on my agenda