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Hello,

A question for the group. I believe the answer is yes or maybe “most of the time”, but just to double check.

I’m making a bridge locator which will hopefully service all the guitar models that I make. It will be a spirit stick style which accepts a proxy saddle in a slot routed into the jig itself. The proxy saddle will then be inserted into the bridge.

I plan to make the arms similar to the centerline finder from Luthier Suppliers. In fact I’ll probably buy the arms from them which I did in the past for a uke sized locator.

The question - the angle for compensation is the same regardless of scale length. Correct? For example, the saddlematic document states:

“These measurements provide compensation appropriate for both short-scale and long-scale steel-string guitars (24-3/4" to 25-1/2" scale lengths). In theory, there's a difference between settings for short and long scales, but the difference is so tiny that it's impractical to adjust to such tolerances (the short-scale settings would be .060" for treble and .150" for the bass side).”

I’m laying out the tool in Vcarve for cutting on the CNC, so I could get super accurate.

Do you folks change these measurements across scale lengths?

P.S. - Here is what I did for ukes, which works really well, but the saddle is straight. I just put the back edge of the saddle on the line and compensate the saddle after the bridge is on.





Brad


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I use the same saddle angle on all of my guitars (1/4” inch difference across 6”). I use a 1/8” deep saddle and adjust the intonation point on the saddle after I get the guitar strung up.

I use the same bass treble slant for all my steel string guitars. Cool tool. I have scratches on my center finder for the different scale lengths.

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I think I do basically the same thing. I’ll post pics in the AM. I use the same comp for all scales. I think the minutiae differences aren’t important when the rubber hits the road...

Brad—

When I cut the saddle slot into the bridge before gluing the bridge onto the top, I would do it exactly like Bob. However, on my last guitar, I experimented with gluing the bridge on, then slotting. I used the StewMac Intonator to plot out precisely where to cut the saddle slot. It worked great! I think I will keep doing this for a while.

The jig you are building would still be useful with this method; you would just index the end of the jig’s adjustable block to the neck-facing edge of the bridge, with the placement measurements accounting for a middle of the road slot placement.

Different roads to the same destination.

I hav a very simple plexi template I made that has a 1/4" piece of wood glued on one end that sits in the nut slot and a couple squares glued onto the sides about half way down to hold it centered on the neck. I have scratch marks on it to indicate the saddle angle, which I pulled form the StewMac calculator web page. I didn't compare the angle differences from 24.5" to 25.312" (my shortest and longest). I can't see an obvious difference looking at the guitars side by side... BUT to me it doesn't matter because I use 7/32" saddles and intonate each string individually with their own take-off point. These end up being different from guitar to guitar (even of the same model) so I just need the angle to be in the ballpark for me to get the intonation results I'm looking for.

I used to slot the bridge to a calculated angle before gluing it on but I was not getting the repeatable intonation results I wanted. I make different body shapes with varying scale lengths so a one-size-fits-all template won't work for me. On the last two or three I've done the same thing Don is doing and glue on the bridge, use the SM calculator to mark the slot and then slot the bridge on the guitar. It has been working well for me too and I'll continue to do it.

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Steve Smith
"Music is what feelings sound like"

Poor man's saddle compensation jig, FB alignment jig. and straight edge.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Thanks for all the feedback and ideas. All the guitars I've built so far I routed the slot on the bridge after it was attached. The thing I'm looking to solve is the whole process, placing the bridge, squaring the bridge, centering the bridge, putting the slot on. It's too fiddly and since I do it only maybe a few times a year at most it's nerve racking.

I want a stick with a slot, put the bridge on, move on.

Ed, here is a link where you've shared your setup before, but the image links seem broken. If you have time to share again that would be great. viewtopic.php?f=10101&t=53168&

Brad

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I like to set the compensation after the guitar is strung up and settles in for a week (month) or two - whenever I get around to it. I use a temporary saddle held in place by the down force of the strings, and periodically check it and adjust it as necessary. Generally it doesn't change much, but since I rout the saddle slot after the bridge is glued to the guitar why not? It also allows you to compensate for the "pull up" and action height, string tension and string gauge used.
I used a plastic plunger from an unused hypodermic needle as a temporary saddle on an HPL back and sided travel guitar I built for camping - any little bit of plastic or wood or metal can work.

Sorry, I forgot I was going to add pics. Don’t know how to fix the broken link so here’s a redo.

My system starts with the bridge blank with the saddle slot routed in. (This is a dummy that is already drilled). Imagine it’s just the blank squared off with the slot.




Then I have a jig that slips into the saddle slot with steel bushings for drilling the holes. By indexing to the saddle slot, then locating the slot correctly with the placement jig, you solve back and forth and side to side in one move.


As in your intonation and side to side string location are both correct as the relationship between the pinholes and saddle slot is a constant.

Then I put a dummy saddle with the top sanded flat into a guitar that I had carefully measured out and verified.

It should be a relaxed slip fit that easily lifts out.

Then I cut a piece of mdf that follows the width and taper of the FB and extends past the saddle by an inch.

On the topside I added a jig that was cut in the slotting jig for that scale with a regular tablesaw blade.

That way you test you’re using the right scale jig by dropping over the frets. It will only lock into the correct scale frets.

Anyway, the dummy saddle should only stick above the saddle by about 1mm. Put some gel CA on top (so it doesn’t run into the slot), then lay the MDF template carefully aligned with the board and press the end into the CA a kick it.

Now all you need to do is put the dummy saddle and the end of the template into your new bridge, lay it on the FB, and your slot and pins will be in the right place.

I’ve never found a need to individually intonate guitars, as I use a stock TUSQ saddle with the correct points already made, the same action height etc. I certainly get no complaints about the intonation and clients often bring up the spot on intonation in their feedback. YMMV.

As the saying goes, sorry for the long post, I don’t have time to make it shorter. Hope it helps and makes sense...







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Muchos gracias, Ed. That repeatable flow is exactly what I’m after. Thanks for (re)sharing the pics.


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Glad to help! Quick, easy to make and use, and saves scads of time. Today I’m kicking myself for not having made a LH version as I sweat it with the ruler and strings while rembering why I made the jig in the first place, lol...

the best way is to make a test jig. nut and 12th fret. Then have a rod that you can move act as the saddle. figure out where to put it and voila. Lots of things affect intonation, mainly action and string gauge. Don't use an arbitrary number. I just replaced a bridge for a friend. Reason? Bad intonation.

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Peter M.
Cornerstone Guitars
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Not to be a pain but if you route your saddle slot slot in the bridge after the bridge has been installed on the ax you can calculate exact saddle placement for proper intonation including for the exact strings one may intend to use, different strings intonate in different places and then mill the slot so that most stings have a compensation point near the middle of the saddle thickness.

That's what we do determine where the bridge goes, glue it with HHG and then calculate where we want the saddle and then mill the slot in the exact place we want it and, as I used to say and still do affectionately - Bob's your uncle.

I'll add that we have not used a preslotted bridge in ten years, maybe more now.

Hesh, that is the way I am doing it now too, since I made my own saddle mill. However, without an accurate mill, the pre-slotted bridge is probably a safer approach.

Hesh,

How are you calculating where you want the breakpoints to be with no slot in the bridge?

Hi Barry,
As I mentioned previously, I locate the saddle slot by gluing an unslotted bridge in close approximate position, stringing the guitar up and using a temporary saddle to find the best location for the slot. Although I agree a saddle mill is nice for a professional repair shop, where time is money, for myself as an "amateur" a simple router jig works perfectly well. It is a bit more fiddly to set up, but time is not of the essence, so it is the low cost solution I use. For a professional guitar maker the pre-slotted bridge may work better for their work flow.

Clay, I had a very similar jig and would even clamp it on a guitar for moving slots, but I got sloppy slots that were not true and would usually have a bit of an extra large slot at the end where I turned the router off. My DIY mill solved those issues. It looks like a Rube Goldberg device, but it gets the job done. I bought linear slides and zero-backlash ball screws off ebay for relatively little cost. I have about $200 bucks of parts in it, less the pneumatic router. I love the ability to dial in the slot with .001" accuracy. I obviously took some inspiration from the Collin's saddle mill.

Goodness, Barry. That is bordering on Steampunk.

When a few of us raided DeanP's workshop a few months ago, I bought a saddle slot mill that Dean had built around the Bosch Colt. It is simply awesome, and works both on and off the guitar. I think a person can get comparable results with the StewMac version, paired with a Foredom instead of a Dremel. I've been very happy with the results I get with my Foredom for this sort of thing. So, yes, a custom mill is wonderful, but I would still favor cutting the slot after the bridge is glued on even if I didn't have one, for the reasons cited by Hesh.

Barry,
You need to hook some stepper's to that thing and let it rout the slots for you!
I used a router in my day job for quite a few years so I am pretty comfortable with it. There are ways to mitigate the little "burbles" that can happen at the start and end of a cut so you wind up with a well cut slot.
But your device is impressive and created at a price the average luthier can afford. Have you ever drawn up plans of it?

No plans. And if I built it again I would make a bunch of changes. I sort of had to design it around the linear slides that were available for a good price.

Very true and good advice. An accurate saddle mill is important and really a must in our business. For Martin service centers like we are there are still a plethora of 70's Martins with the saddle slot in the wrong place. An accurate saddle mill makes invisible plug and recuts a piece of cake.

We have a couple long calipers with dial indicators that we used for scale length calculations. We tooled up for saddle slot locating because of the Collins Saddle Mill and Dave has been doing a study of f*ctory saddle slotting and developing a forensic tool for among other things verifying an instruments authenticity in a dispute. f*ctories slotted to templates repeating the same levels of accuracy... or not over and over again and we can measure where every fret is and compare it to our database with around 400 valuable guitars in it now.

The raw calculations are on a chart in the shop so at my age I'm not going to quote from memory fearing a mistake and someone acting on what they read here. But we used convention too measuring between the D and G for the scale length and then compensating to our data that we've collected.

I do it empirically with the Stewmac Intonator and an accurate electronic tuner.

https://www.stewmac.com/luthier-tools-and-supplies/tools-by-job/tools-for-measuring/the-intonator.html

You can also use small pieces of nails but they tend to shift position under string tension.