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Wanted to do a short description of one of things we do from time to time and this was an interesting one in that it's an early 50's OOO-18 Martin player instrument. This guitar is in service professionally and gets a lot of playing. It also has some value, not a lot, not a little but it is a valuable instrument.

Part of the set-up was lowering the saddle to get the action where I wanted it and the owner wants it. In this case for this style of guitar and how this player plays we are targeting 4/64th" high e at the 12th and 5.5/64th" low e at the 12th. Please excuse my combining of decimals and fractions it's how Dave and I communicate with each other and it works for us and is self explanatory.

This old Martin has a through saddle that was not glued in, thankfully and that's because we made it years ago and with our fitment, snug there is possibility of the saddle falling out. If it had a UST we would have a looser fit on the saddle so that it can go up and down on the UST freely and is not binding in the slot. For through saddle instruments since we have a Collins Saddle mill we mill a pocket in a pocket so to speak permitting through saddle instruments like this one to have a UST with the through saddle remaining with the original look and eloquence.

Step one for me was doing the math and evaluating the instrument with strings on and tuned to pitch to see what is before determining what could be. There is no truss rod on these so I have to nail the adjustment at the saddle. This one came in with action of 5.1/6.1 (5.1/64th" at the 12th high e and 6.1/64th" low e at the 12th).

Normally it's adjust the truss rod, cut the nut slots and then do the math. In this case I cut the nut slots and did the math.

Although this is not high action by any measure it was high for our client as he ages and loses hand strength. So we decided to go with 11's "custom lights" to help him out and lower the action to the spec I use for most OMs and guitars of this body size 4 and 5.5 or 4/64th" and 5.5/64th", we always state the treble measurement first.

Interestingly this guitar has never had a neck reset and it's 70 years old. Pretty cool. The bridge has string ramps already milled in it which will help greatly with break angle on a low saddle.

So part of doing the math is to determine the fret board radius and the existing saddle radius to find the radius that I want to use for the saddle top.

With all this done I marked the saddle with dots that I want to make disappear with my files and that will be the height adjustment. My dots are made with mechanical pencil that I still sharpen on sandpaper so I have smaller, more precise dots.

The guitar is protected and I forgot to get a pic of the heavy leather that I covered the top with before using the files. We use files a lot and although I could have removed the saddle and done this with it upside down on a belt sander or disc sander I prefer to sneak up on my goals with files.

Not shown all our work is securely clamped in our leg vices.

The saddle is filed to my dots and then removed.

It's then recrowned with the StewMac diamond crowning files which, if you did not know, crown saddles great. I then broke the edges of the crown with OOO files and 320 paper.

Finally the saddle was buffed on our nut buffer taking care not to buff the sides that will be in the bridge and not shown as to not mess with the fitment of the saddle to the bridge.

And here is a pic of the results. These were historically not compensated so I didn't do that and the guitar didn't need it.

Action is right at the target now with 11's and tuned to pitch at 4/64th" and 5.5/64th" so she came out great. The saddle looks eloquent and is nice and shiny with zero scratches showing, no gaps around the slot and the through ends are flush with the bridge just as Martin intended 70 years ago. This looks like it came from the f*ctory.

You can see too that there is not much saddle left but enough of a crown to work pretty OK. Neck reset time will come and we are nearly there but for now this will keep this nice old guitar singing pretty for some time to come.

A small operation for sure, took me about 25 minutes.

Thanks for looking

Thanks for calling that out. When I first scanned the pics before reading your text this stood out to me, that the dots didn’t show compensation as normal, at least not the B, etc…

When you say the guitar didn’t need it I’m guessing that means it’s not the normal fine tuned work you do but “good enough” ? If so, what does good enough mean in this case? Just curious.

Thanks for sharing these, I always learn something new.

Brad


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At roughly 0.015" change in string speaking length per cent of pitch change at the 12th, and roughly .030" total unusable on a 3/32" saddle, that leaves just over 4 cents maximum pitch change adjustment for saddler compensation. Why the 0.030" unusable? Sharp edges in bone with steel strings do not hold up, so a minimum of 0.015"-0.020" setback from the edges of the saddle are necessary for longevity. Also keep in mind that some earlier Martins are even narrower in the saddle, with every one of the pre-1900 instruments in the shop the last time I was over wearing quite narrow saddles.

Given 5 cents is the usual difference given between pitches needed to detect flat or sharp single notes (unison strings are aided by the beat frequency change, so somewhat less than 5 cents), a rounded top saddle will provide not much over 2 cents adjustment either way. A string that was 6 cents out could be compensated to 4 cents flat or sharp, but no more. Ther is also the usual player dynamics to consider, which can easily increase pitch of a fretted string by a couple of cents, either moving the string into perfect intonation on a flat string or a barely there sharpish string into a standout note in chords or arpeggios. A wider saddle possesses more adjustment range, but on vintage work, there's less tolerance for appearance changes.

We seem to see most through saddles coming into the shop glued in (these days from Martin with CA!!!), so a mill bastard file and two of Mr. T.J. Thompson's saddle rounding scrapers (one slightly reduced for really low saddles) make adjustment quick and easy. It is also possible to fashion old scrapers or saw plate into custom radius saddle to scrapers for low work.

https://proluthiertools.com/product/saddle-top-shaper/

Mr. Thompson also has the only truly rigid router bases for pencil grinders I've seen, although they are priced dearly. He also offered cutters for milling bar fret slots, which is quite useful for those shops like ours doing bar fret work.

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Fortunately people realized what a bad design the through saddle is and stopped doing it…

Brad

See Woodie's excellent post and there are some numbers there worthy of being on the wall above people's set-up benches such as the mention of 5 cents.

The range of adjustment on this narrow a saddle may not be audible to we human bags of mostly water. Hence.... good enough. Also intonation was not a problem it sounds great and no measurements were taken, that was not the mission.

Great post, thank you Woodie.

I did not know about this tool and will have to get one so thanks for that too!!

Exactly Ed and I'll add it was adopted because it was easy to manufacture but it sure is not as serviceable as a drop in saddle. These were used before the advent of the under saddle transducer making pick-up choices more limited.

Makes sense. +\- 4-5 cents has always been the target for me, I believe that comes from the class as well, Hesh.


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Good and exactly we did talk about this in class. Like Woodie said 5 cents is believed to be the threshold for human hearing to discern that the intonation is beginning to be flat or sharp. Press a little harder and it's a little sharper and vice versa. Meaning player technique can take intonation out of the discernible range and back in it if the instrument is close ..... enough.

Robert Johnson and many others of the greats had guitars with action high enough to slice hard boiled eggs. This created intonation problems too.

So again very low nut slots that do not contribute to intonation problems at the nut end of a steel string and the math for speaking length of the strings and the intonation can be good enough. I also mentioned that this one is not ready for a neck reset yet. When a guitar needs a neck reset the intonation is often off enough to tell when playing it as the speaking length of the strings is shortening.

There is a case to be made too that a saddle with only the crown proud of the slot would look funny compensated and certainly not vintage accurate.

And you know how I feel about "mission creep" we do lots of extra stuff on people's guitars but only when we think it's appreciated and needed. This one didn't need compensation and sounds great. It's actually a guitar I would love to be the steward of for a while because as Neil Young says in the tune "This Old Guitar" we are just one of many who will enjoy these as they live on.

Lastly working on valuable vintage stuff is a bit different. You don't overstep and less is more. Repair ethics might be a good thread here someday.