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The scale length and therefore the intonation is noticeably off on my main performing guitar so I would like to plug the saddle slot and re-rout it with a dremel. Does anyone have plans or ideas for a saddle routing jig? I see Stew Mac offers one but it's $170 or so, and I figure I could make one and save some money. Any other advice, pictures, recommendations would be most helpful. Thanks.

how do you mean, "the scale length is off"? also, is it a steel string or classical style guitar?

Steel string, Martin Dread, 25.4" scale. The scale length is 4 or 5 mm too short so it goes sharp by 20 cents or more when fretted at the 12th fret on the low E string.

You would be just as well to widen the Martin slot to 1/8" and use the thicker saddle. As for a jig the Stewmac style or similar would be easy to make though a straight guide could be double sided taped to the bridge as a guide for the cutter.

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Fred Tellier
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4 or 5 mm is quite a bit. That's in the neighborhood of .1875 ".
If you moved your saddle .1875" back, the string break over would be extreme. What's your measurement from the 12th fret to the center of your saddle? Clinton

It's your main performance guitar, so you'll want to give this some careful thought. If you've not completed this procedure before I would recommend you either take the guitar to someone with more experience, or find a beater guitar and practice the entire process a few times before you proceed.

That said, here's a thread on the topic:

viewtopic.php?f=10101&t=27796&hilit=saddle+slot+router+jig

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George :-)

Clinton - I will have to check that measurement when i get home later. George, thanks for the link. I took the guitar to my friend who is a professional luthier and he says with my experience this is a job I can handle but will help me out if needed. Worst case scenario I would have to put on a new bridge, which I may have to do anyway.

I looked at doing this on an HD-28 I had a couple of years ago. I determined that moving the saddle back enough to solve the intonation problem would put it too close to the pins. A new bridge, moving the saddle and pins to a more suitable location, would also mean a new bridge plate. Too much effort.

I ultimately ended up selling the guitar and took to building myself one from scratch. =)

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Jim Hansen

All you really have to do is plug the hole, and overlay the holes on the bottom with additional bridge plate material, no need to do a replacement.

Or you can always plug with maple which solves that problem.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Here is a piece of paper mock up representing the correct location of the saddle (1954 Martin D-28, 649.0 MM bass to 646.5 MM treble from Nut to center of saddle). I think I already know the answer to this question, but what do you think...saddle too close to the bridge pin holes? click on picture to enlarge....

those bass strings are going to break pretty hard over that saddle, making the pins want to pop out, no? seems like moving the bridge back would be a better solution. i still cant figure out, if the neck is still set in place, how the bridge could be in the "wrong" position, unless they screwed up at the factory??

If you dont want to move the bridge, maybe you could move the fretboard towards the head. Cut a sliver off the nut and some off the fretboard. Just an idea.

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Jason Moe
LaCrosse WI 54601

Moving the bridge compared routing a new slot would be a safer option. That is, notwithstanding exposing the covered portion of the top plate. I have done it before ... the processes starts with

1. Bridge removal
2. Plug the bridge pin holes with wood putty
3. Re-measured the correct position of the saddle
4. Touch up the top plate's bridge areas
5. Re-glue bridge in new position
6. Re-drill bridge pin holes
7. Set up and good to go

If you must re-route the saddle slot, perhaps practicing on another subject can increase the success rates. Anyhow, best wishes and I hope for a positive outcome. Cheers.

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Regards
aDAM

i'd check inside the guitar to make sure that new pin holes wont cut the X-brace inside. If its that far ahead already, chances are you will have plenty of room the other way. You never know.

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Jason Moe
LaCrosse WI 54601

Before you do the surgery on the bridge check that
-12th fret action is where you want it
-neck relief is not excessive, I like it low at 5 to 10 thousandth of an inch
-Nut slots are not too high

These can all make intonation worse and are worth fixing before modifying the bridge
Also check whether the fretted notes on the first few frets are sharp, you may be able to apply some nut compensation which will help all the way up the board and reduce what you need to do at the bridge.
I know 70's Martins were notorious for misplaced bridges, thought 50's were generally ok

Here's a couple of possible approaches:

First Approach:

As Todd says, you will need to move the saddle back by ~3.5mm to correct a 20 cent error. Looking at the pics, the bridge has moved up by ~1mm, maybe more, so I would be taking the bridge off to put it back over its original footprint. That's 1mm won. As the bridge has to come off, I'd make a new one with the saddle slot in the correct position, but when drilling the pin holes I'd angle them so that the bottom of the holes in the new bridge are over the original holes in the guitar top and the holes you see in the top of the bridge are about 2mm further back. So you've now only lost ~0.5mm between the saddle slot and the pin holes, with no work on the bridge plate. You can angle the back of the bridge so that the new holes are close to perpendicular to the top of the bridge.

Second Approach:

If you move the nut towards the sound hole by 2mm (which will generally lead to an overall intonation improvement anyway, but is about the max you can go without some significant analysis) you will reduce the intonation error by 3 cents per mm moved, i.e. 6 cents. You can do this by using a bone ledge in front of the nut as a sort of nut forward extension. So now you only have 14 cents to find, which is a saddle movement of 2.5mm. You might be able to get this by filling the old slot and re-machining (but I'd still be inclined to put the old bridge back over the old footprint, which finds you 1 mm anyway).

Here's a third bonus approach:

Go full nut and saddle intonation (like this: http://www.goreguitars.com.au/main/page_innovation_summary_nut__saddle_compensation.html) and you will require an un-slanted saddle slot which will fit OK with the bridge in its present position, but a new saddle slot will be required, parallel to the front of the bridge. The bulk of the nut (before the steps are cut) is 3mm closer to the first fret. It's a great technique and gives much better intonation than standard, but you'll need to read up on it!

Which to go for is going to be dependant on your budget and skill levels. If you've not done this type of work before, take the guitar to someone who has.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Thanks for the thoughtful reply guys. After some thought I have decided to sell this guitar and build one for myself to spec. This is a bit more work than I care to do myself on an expensive vintage guitar.

And so it begins! =D

This is *exactly* how I got started building.

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Jim Hansen

Don't have/can't afford what I want. Gee - I'll just build it. Next thing you know you are fully infected with the dreaded disease.

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Steve Smith
"Music is what feelings sound like"

How true. And there is no known cure, just a continued treatment of build after build. Oh the inhumanity of it all!

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.