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Hey everybody

Received a 1949 D- 18 Martin in my shop for evaluation. Seems the bridge may be incorrectly placed from the factory. Problems:

1. bridge has been thinned , and , saddle height has previously been lowered , to improve high action , when a neck reset would have been the ideal solution.

2. 12th fret intonation check indicates the correct position for the saddle @ treb. E string  to be about 1/8 in. toward soundhole from current position. This is not even over  the bridge.

3. same situation for saddle @ 6th string...saddle should be about 3/32 in.  toward the sound hole from the original position.

4. Martin indicates a scale length of 25.4 in is appropriate for pre 1960s.

5. My measurements ( using a stewmac saddlematic ) keying off the 12th fret ( nut to 12th and using same measurement from 12th toward bridge ) place the saddlematic treble wire marker at 1/32 in. shy of the bridge ; and, 8/32 in. shy  from the crown of the saddle where the 1st string crosses.

       Have any of you run into this on the D-18s before? Or is this particular D-18 just a friday made guitar .

       My 13 years of repair instinct tells me that the bridge is in the wrong place . That I should make a new oversize width bridge ,and , cut the saddle slot in the correct new position. Oversize to cover up the bridge footprint outline on the top.  BUT THIS IS A 1949 VINTAGE MARTIN we are talking about here. Although I have much experiance in all phases of guitar repair, and feel that the intonation would be much improved , and a neck reset would greatly enhance the playability of this instrument,  I am more than a little apprehensive about ruining the value of this instrument by making necessary design improvements on the bridge.

Any thoughts ?

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I'm not sure I understand what you are talking about Dale. Once you have removed enough material from the heel to shift the neck as much as you need, the dovetail (tenon)  will need to be adjusted so it doesn't "bottom out on the back of the mortise (neck block). Along with that, the dovetail taper will need to be adjusted but it will need to be thickened, not thinned. The area where the taper meets the heel isn't going to be thinner than it is now, it should be the same thickness as it is now because the mortise isn't going to change. You will need to add some material to the existing slopes of the dovetail then fit it to the mortise. In other words, as you push the dovetail deeper into the mortise you will create a gap which will need to be filled. In essence you will need to "shift" the existing dovetail back towards the heel by the same amount you removed from the heel to make it all fit. The only way I see to do that is to add material to the sides of the dovetail and fit the new material to the existing mortise.

 

I don't think I would consider removing material from both the dovetail and the mortise. "There be the way to madness."

 

BTW, you will probably have a bit of extra finish touchup around the heel once the joint is complete since the removal of material on the heel will narrow it just a bit.

I have never done this repair, but I think You should start with adding wood to the tenon-sides and the added wood should be glued snug up against the current heel. After this You can cut the end of the tenon, and it seems to me You should cut the amount of wood corresponding to the distance You aim to move the scale.

 

After this You can start working on the heel and also there the amount of wood to remove is just enough to allow for the movement You aim to achieve. I would remove the same amount of would from top to bottom of the heel to start with, after this You have moved the scale without adjusting the neck angle. Once this is done start shaping the new tenon to make it fit and after finetuning the neck angle You will need to shim the tenon sides some more.

 

Reading what I just wrote I admit it seems a bit awkward but I think this is how I would do it, not to weaken the tenon. I wouldn´t touch the neck block.

I think you guys are over analyzing this. You don't need to add wood to the heel tenon, you just add proper thickness shims to take up the slack. generally the dovetail opening in the body is cut large enough that it doesn't have to be enlarged at all, and if anything you remove material from the neck not the body.. You may have to remove a small amount from the end of the fretboard so it stops in its original position.

I'd also leave the intonation slightly flat to compensate for the use of a capo and the fact that the string gets stretched just from fretting it. If the scale is off 1/8" I may only change it 3/32"

It doesn't take that much wood removal from the heel to correct this problem.

It's not time consuming to accomplish this, as some suggest.

 

Jim  

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