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Slowly I’m making my own parts, but the bridge is something I still buy premade and preslotted. I’m just concerned that I’m not getting them exactly in the right place. I’ve been measuring the 12th to the nut and then going toward the bridge w that same measurement and putting it in the middle of the saddle (so there is one end higher and one lower because of compensation). I square the bridge to the fingerboard, which is square to everything else.

Am I going about that right? I’m getting some good sounding instruments, but I’m still not as good as I’d like to be as far as intonation goes.

I suppose I just need to start making my own then slotting them after glue up.

Any advise is appreciated as always.
Thanks
B Snow


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I make my own, it's not that hard. A bit later I will post my system for bridge location but I got some sanding to do first...

For a quick reference, stew macs fret calculator will give you actual compensated string length. So getting the length high and low string will give you your angle. My slot angle back 4mm across the 71mm length...

I’m just concerned the compensation isn’t matching up when I square the bridge


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Actually what you want to do is add a little bit of compensation to both ends of the saddle. You should add about a 1/16th- 3/32 of an inch to the measurement of nut to 12th fret distance and use this measurement to place the treble end of the saddle slot from the twelfth fret. The bass end of the saddle slot is generally nut to twelvth fret plus 1/8th - 3/16ths inch. String gauge and action will affect the amount of compensation some, but as a ball park measurement for 25.4 scale and common steel strings that should be close.
The StewMac fret calculator also gives you compensation numbers for the ends of the saddle slot from the nut to saddle and may be less confusing than what I have written above.

I really should have this nailed down at this point already. Thanks for not making me feel like a total noob ha:) the SM calculator seems to be the goto.



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As a side note:
What you are compensating for is string stiffness and as strings become shorter they act (slightly)more like a rod and less like a string and go sharp further up the fretboard. All strings have some stiffness so the compensated length is always longer than twice the distance from nut to twelfth fret. Even nylon strings benefit from a small amount of compensation.

And when you say “compensation” you’re just saying add to the length right?


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Yeah, at the saddle compensation is always an addition to the length. Compensating the nut is a bit more arcane and most of us avoid it except to a very generalized and limited extent (it doesn't improve things all that much and can be string type specific).

Using pre-slotted bridges I would think the saddlematic would be a wise investment. Make two shims to set the compensation on the pins and then set the saddle slot so that the pins meet the front edge.


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I actually do have the saddlematic, but I’ve read things that suggest it isn’t accurate in its design ??


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He mentioned doubling the length of the 12th fret to the middle of the saddle, so I believe his saddles are probably naturally compensated at the bass and treble due to the angle of the saddle slot.

When I was using pre-made bridges, I used Stew-Mac's Saddlematic to locate them. I was always really wigged out about the bridge sliding around or just not getting the slot in the right place, so I get where you're coming from. Think about investing in a 36" PEC blem rule in 16R. Totally changed my bridge life. You'll be able to look at the measurements from the fret calculator and locate saddle position perfectly. Measure along the string path to the center of the slot for your high and low E's.

Man thanks i LOVE gear that makes things precise


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I agree with adding a 36” 16R rule to the process. Such a rule, used in conjunction with the center finder and bridge squaring attachment from Luthier Suppliers (link below) can really make bridge placement a more precise and less stressful job.

Link:

https://www.luthiersuppliers.com/lsprod ... ine-finder

I have and use this... but I’m always still concerned the preslotted bridge isn’t at the right angle or something


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The rule suggested will be here Monday. Hopefully that along w the bridge square tool will give me some peace of mind on this:)


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Well, there is another way to verify you have it in the right spot. You can rig up a temporary tailpiece that clamps to the tail block area. Install the tuners (at least the E strings). Install a saddle in the slot, and put the bridge in what you think is the right spot. Tune up the E strings. See what the intonation situation is. This isn’t perfect; the string tension won’t be the same as the real thing, there won’t be bridge tilting like the real thing, etc. But it can help make sure you are not wildly out of whack due to a math error.

I would be interested to hear about how the saddlematic is inaccurate. I can’t imagine an easier tool to use to place bridges. I slot after the bridge is on but still use the saddlematic to sanity check where the slot will fall.


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I’m with Brad on wanting to know the reasoning behind the notion that the Saddlematic is inaccurate. I think pilot error is a more likely explanation for any problems using it. You do have to be careful about how you determine the extension of the pins from the block, and to what part of the saddle slot the pins are supposed to extend. If you are careful with those computations and adjustments, it is a very useful tool.

We use the Saddlematic to set most bridge slots, bu have several Starrett 24” and 36” 5R rules to check placement. Concerns with Saddlematic:

- Correctly setting the compensations on the saddle locator pins with regard to scale length, strings, and nut compensation.

- Consistency in registering the 12th fret registration groove against the 12th fret

- Use with zero-fret, fan-fret arrangements

We use 0.020”- 0.025” nut compensation on most steel strings (depending on string set), so that needs to reflected in the saddle locator pins. By default, most preslotted boards have 0.012” nut compensation (half the width of the saw kerf) with most of that obviated by nut fabrication or wear over time.

Concerns with use of a rule:

- Use of rule end as starting point of scale (amazing how many nuts have 5, 10, or even 15 thousandths worth of adhesive residue, forward or rearward lean, or other issue making this measurement more of a challenge)

- Parallax error

- Operator read error (failure to adjust measurement for extra inch or cm for zero scale length measurement.

Once set, the Saddlematic eliminates most rule use errors, but it is important to understand that other potential error (e.g., error in nut face registration: use of 11th or 13th fret for setting scale length, failure to properly position the fixture. We use it, along with a centerline finder to locate most bridges and set archtops, etc.

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One thing to keep in mind is that compensation adjustment requires the - least precision - of all the fretboard/string length calculations. Depending on the strings chosen and the height of the action (two parameters set by the player) the ideal compensation will change. For that reason, on a non adjustable saddle an "average" compensation is usually used. Since it acts over the entire string length a slight mismeasurement will have less effect than that same amount of mismeasurement elsewhere. Which is not to say one should be "sloppy" about it, but that it is less critical for it to be perfect.
To set the saddle location I use an aluminium yardstick and measure along the string path of the treble and bass ends of the saddle. Aluminum has a lineal thermal expansion coefficient about twice that of steel but it's still accurate enough for what we are doing. After the bridge is properly positioned I tape around it, adding a couple of extra layers of tape along the front edge for the bridge to rest against. Aside from determining the bridge location the tape also helps with glue clean up.
I generally cut the saddle slot after gluing on the bridge (not always) but I have found this method to work well with pre-slotted bridges also.

I too am interested in the problems with using a saddle-matic. I can't really see any and that is always dangerous. I don't own a saddle-matic but I made a tool that is very similar. I used pins the same thickness as my saddle slots and use them to locate the bridge with the saddle slot already milled.

I mill the slot in the bridge with the compensation angle I want and mark the centerline of the bridge. I set the compensation on the two pins the desired distance away from the leading edge (that first registers against the nut surface) to the center of the pin. These pins are sharpened to a point making it easier to measure to the center. When I flip the tool around to face the bridge side, I put the pins in the saddle slot and verify the center of the bridge is at the center of the top then mark the bridge location. This thread has me worried that I am missing something.

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One thing to note when using the saddlematic, on the StewMac website instruction page for the saddlematic they give compensation numbers for the -front edge- of the saddle, but on the fret calculator page they give you numbers for the high point ( break angle - usually center?) of the saddle. Using the fret calculator numbers and always centering the cut gives a little leeway both ways for intonation adjustments.

Yep, that's what I had in mind when recommending the saddlematic for pre-slotted. It's set to the front edge of the saddle so on a pre-slotted bridge slide the bridge up until the points are just on the edge of the slot, center it, square it and mask off with a few layers of tape to make the guard rails. Glue that sucker on!

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B Snow,
I'm sure you have all the answers you were looking for by now, but what the heck? I'll add one more.

I make my bridges since the second guitar, I install the bridge and then slot it, but for a premade/slotted bridge I would:

Using the StewMac calculator and a little arithmetic (the average of the compensated 1st and 6th is, of course, the center of the saddle), find the distance from the 12th fret or the nut to the center of the saddle. Place the bridge on the guitar making sure the center of the saddle is on that mark. Then using a drafting triangle, make sure the bridge is perpendicular to the centerline of the guitar. That will give you a good location for the bridge. Depending on who made the brige the 1st and 6th string positions may or may not be right on the StewMac dimensions, but once you compensate the strings you should be good.

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