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I located the slot using a saddle cut down to 1/8 and adjusted the 2 Es, and surprisingly, the Stewmac jig that I made doesn't agree. It's about 1/8 off.

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Hutch

Get the heck off the couch and go build a guitar!!!!

Saddlematic marks the front of the saddle per the SM instructions.

Were you 1/8” off in the neck or tail direction?


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There is compensation to add too. And when you say you located the saddle do you mean you strung up the two e's, tuned to pitch and found the correct intonation points for the saddle this way or was it a measurement?

Strung ip the es and tuned to pitch


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Hutch

Get the heck off the couch and go build a guitar!!!!

Whenever I get an error that is identical to the significant dimension of some component along the line of measurement, it's usually a mental error where I use the wrong side of that component as the reference or add versus subtract. Sounds like the Saddlematic is set for the back (tail block side) of the saddle versus the front (sound hole side).

Was the action high?

Keep in mind that the low E breakpoint goes toward the back edge of the saddle and high E goes toward the front edge, to make way for the step between G and B. Although that should cause at most 1/16" discrepancy measured at the center of a 1/8" saddle.

What intonation method did you use with the test saddle? Match frequency of 12th fret and harmonic? Measure all notes and minimize error?

We really need photos and measurement numbers to get to the bottom of it.

There's lots of geometry going on at the bridge saddle juncture that all has to work together. Jigs, rules and straight-edges must all come into play. And it all deserves to be triple checked before any holes are drilled. What's done there will make or break an instrument and not a good place for short cuts.

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Brian R, Wood Mechanic
N8ZED

I never use a jig on the bridge / saddle location. I have learned that often when I had an issue it was always the jig so give me a good scale and I use that to measure things out.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

We used story sticks extensively in Hab construction to avoid repeated measurement for good reason: because that is where errors tend to occur due to transcription and incorrect origin. Give a volunteer a story stick and tell her to mark every stud 'stick on sill' produces repeatable markings to get chair rail blocking set in. The volunteer does not need to recall multiple measurement, not does she have to make them repeatedly. Provided the single original story stick was made correctly, those hundred of opportunities for errors to be made are avoided. This applies in nearly any setting where repetitive measurements - whether identical mark-outs or variations - are necessary.

While Greenridge never used full length bridge setting templates such as those which led to the 1970-1975 miss-set bridge debacle at Martin, we did use the Saddlematic on just about every instrument that came in the door. Whether to validate correct saddle location or to set new or repair bridges, we avoided the tedium of determining scale length, sussing out the original builder's actual compensation, and identified a whole bunch of those Martins already mentioned with bridges in the wrong place (plus a few newer Martins with iffy saddle placement).

The value of the Saddlematic or similar 12th fret-referenced tool is that - provided you can find the face of the nut and the 12th fret, the measurement for the saddle location will be correct for that instrument's ACTUAL scale length without the need to read, record, and mark out several measurements. While we kept the intonation pins set to produce close to the Martin standard saddle skew, it was easy enough to add the additional length on the bass side to mimic Gibson and other extended bass-side adjustment with a feeler gauge shim.

For a shop doing repair work on just about any fixed or movable-fret instrument, we resorted to actual measurement for far fewer instruments than I would have ever expected, and usually where no 12th fret reference was available. We found a number of errors on both production and custom instruments, but I don't recall the need to redo any bridges or saddles due to our own errors. I do recall a number of times where stated instrument scale length was not anywhere close to actual 'as built' scale length - a task expedited with the Saddlematic. Working with a couple engineers over the time I was at Greenridge gave me a healthy appreciation for the necessity of precise layout work, as well as the range of errors to be avoided by minimizing measurement to that which is strictly necessary. I still have Mr. Stock's back-up 6", 12", 18", 24", 36", and 48" Starrett 5R rules at my shop (and really need to get them back... after I find a few more of those nice satin chrome flex ones).

Story stick is the way to go. Bang on every time. I added a vacuum drilling jig to the mix to drill the two e’s.

https://youtu.be/YIE2sWfX2p8?si=MYF-gtNj8AhRGbV4

Brad


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I measured again, and now the string is in tune using the saddlematic and checking with a slice of saddle. I don't know what I may have been doing wrong yesterday. Oh well, that's the way she goes.

I made this out of a discarded cutting board. I have the expensive SM 3/32nd, so I don't have to widen the slot like I did before. I'm waiting on a 1/4 to 1/8 collet reducer. Suppose to arrive today. I want to use my trim router instead of the dremel for a better cut.

The other issue is that the slot is really close to the front of the bridge. I'm going to nudge it a little further in and deal with it when the saddle is in.

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Hutch

Get the heck off the couch and go build a guitar!!!!

I’m going to make a few suggestions about your slotting jig. Please take them as having the intent to help, not criticize.

I’m not there to evaluate in person, so this fear might be unfounded, but having the cutting board sit on top of wood scraps, which themselves sit on the guitar, feels like a mistake-prone setup. The wood could scratch your finish. The whole thing could come loose, since cutting boards are made of a low friction material. The cutting board is unsupported in the middle, which could cause flex in the middle, which could cause the slot to not have a flat bottom.

I have a slotting mill (made by a former OLF-er; bought it when he hung up the hobby) that has an aluminum base. To keep it from scratching the top finish, as well as deal with the slight arch of the top, I place it on top of several 1/8” thick leather scraps. This is the really thick leather. It doesn’t flex too much; it doesn’t scratch the finish; it helps the jig span the top arch; it grabs pretty well. Leather is just ideal for this sort of tool-to-instrument interface (true for lots of other things around the shop, like vice jaw liners).

I suggest you remove the wood scraps that you have placed underneath the jig and replace them with leather scraps. If you find the cutting board is flexing in the middle, you can maybe thin a piece of leather a bit and stick the thinned piece close to the bridge.

Good luck with the slotting.

I'll take all of that into consideration.

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Hutch

Get the heck off the couch and go build a guitar!!!!

The human species seems to have a trope for impressive arrays of complexity. Problem is, this can be a lot of wallpaper. I'm guessing that the Saddlematic doesn't get more appreciation as a result of its simplicity - - - how can anything that simple be good for anything? It's its own version of a 'story stick', something repeatable and consistent that doesn't need rulers, calipers, incense, or turn-your-back rituals to do its job. Once the hooks are set in place to account for a given saddle thickness, onward, just get the bridge centered relative to the fingerboard. And once the tool is adjusted for a given saddle thickness, no more adjusting, just use it.

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Peter Havriluk

Woodie wrote:
"The value of the Saddlematic or similar 12th fret-referenced tool is that - provided you can find the face of the nut and the 12th fret, the measurement for the saddle location will be correct for that instrument's ACTUAL scale length..."

Assuming the nut has not been compensated as well. even when that's not the objective some fretboards are just cut off a little short at the nut end. These days I go by the 1-12 distance most often.

At one point a friend gave me printouts of every scale from about 60-70 cm by .5mm intervals. You could measure fret-to-fret on some of the 'by eye' scales that used to be common and find the one that matched most closely, requiring the fewest re-cut frets and minimal relocation of the bridge. I wonder if some luthiers ever bothered to clamp the rule down when marking fret slots: you'd see a shift of about 1/2 mm at one point and the rest of the intervals would go on from there.