Compensation on a one-piece bridge

Bruko One-Piece Bridge Compensation

Hi,

I have a question for my fellow luthiers. Most all my experience is with guitars and bridges with separate saddles. This is a one-piece bridge and I need to adjust the compensation. How much adjustment needed is shown in the four attached pictures, one for each string.

There's two ways I can go (that I know of and know how to do).

1) Sand the saddle down, make a jig for my Dremel router base, cut a saddle slot and make a compensated saddle. I've done this a few times making new bridges for guitars.

2) Since I need to lower the action a little (it's at 3 mm now), adjust compensation by selective sanding of the fixed saddle.

The second option is easier, but it doesn't allow for much, if any, future adjustments. The first method leaves more room for future adjustments, but carries more risk and is more work, i.e. setup and making a compensated saddle.

I'd like opinions from you who have experience doing this sort of thing with ukuleles. Also, if there's another option I haven't thought of I'd like to hear that too.

TIA!

Edit: I should say this is my own instrument, not a customer. It's a 20 year old Bruko soprano, solid maple with rosewood bridge/saddle and nut.

A bit of hand shaping of the saddle is par for the course.

I’ve come to think that adjusting Bruko saddles is almost regarded as a ‘no no’. Perhaps it seems contrary to the nature of the instrument and simple build, or perhaps it’s considered too risky or even just unneeded. IIRC someone posted here about contacting Bruko with concerns about poor intonation with particular strings, and the response they received from Bruko was don’t use those strings - logical enough I suppose. To be fair complaints about Bruko intonation are rare here and if I found a reasonable condition second hand five or six going for half the new price I’d buy it ASAP.

Perhaps the saddle is slightly out of position or perhaps you’re expecting more from the Bruko than it’s designed to give (tuners have changed in accuracy whereas the Bruko design is an unchanged classic). If, like you, I had a Bruko then I’d be tempted to sand the saddle down to give me just a little under 3 mm action and then I’d chamfer across the whole width of the saddle - at say 20 degrees, so shallow - to get somewhere near the desired intonation on the ‘A’ string. Before doing that be sure to fit a good set of your preferred strings - many folk have positive experiences with Worth Browns on the Brukos. After that I’d call it a draw and just enjoy playing my Uke.

(Should I have sanded too far then, after kicking myself, I’d glue a thin wooden shim onto the upper face of the bridge and try again. You will already know but for others the rear side of the saddle area must slope slightly away from the strings’ points of contact too or during vibration their effective length can be compromised - there is a reason why saddles and frets are typically rounded.)

I’m not a Luthier but I have used hand tools a lot and hope that my suggestion is still of assistance. I hope that you get better responses, in part I responded because others hadn’t.

Thanks, Graham, hadn't thought about gluing a hardwood strip on the saddle area. May not actually need to glue it, or just spot glue glue with something easily removable like I do my nuts (!). Sounds like a good compromise. I do need to adjust the intonation. It's just a bit too "out" for me - especially the C string. And as long as I'm doing that I want to lower the action .5 mm or so.

Also, I do have a bit of a problem with the break angle, but I'm sure I can fix that by cutting the slots a little deeper.

Thanks for the idea!

Edit: The more I think about it, the more I like this idea. May even make 4 small ones for easier placement for individual string compensation.

I’m glad that my thoughts and ideas have been of some assistance.

There are, I think, several worthwhile ways forward.

With regard to both the shim strip or individual pieces option there’s the question of material and number of pieces. Some while back I saw a custom compensating bridge and saddle that Mr Timms had made. The saddle was in two parts within the bridge, one saddle and slot angled for the a,e and c strings and a seperate slot and saddle was there for the g string. Using that (angled) concept you would need only two strips. As for material you, as a Luthier, have the options of wood, metal and bone - hard material is the usual choice for a saddle. Thin sheet hard wood is obviously available, frets could have their base filled away and bone comes in various forms and thicknesses. As an amateur one's options are less, though I can think of several.

As a bridge should, I think, be well bonded to the sound board (for the most efficient excitation pathway to the sound board) I suggest that you apply the same logic to any narrow splint or full width shim, etc. - have the flattest mating surfaces and best excitation path possible. For what you might want to do with a full length and width strip I suggest that you establish the ideal break points first, with suitably thick wire (as per your photo’s), and then work on the wooden ‘saddle’ strip with (wide slotting) nut files or small needle type files to replicate those positions.

If and when it is possible then it would be really interesting to see your finished modification / repair, and potentially helpful to others too.

I've lowered the saddle height on Brükos a few times and I always lost surprisingly much volume. Most of it reappeared when I adjusted the saddle for improved intonation. I can't explain why that happened but it did.

In your case I would use a sharp chisel or a gouge and back that leading edge off as you show in your pics. The result might resemble the one piece bridges I make for my piccolo ukuleles, I'll look for a pic right away.

In this post on my blog there are a couple of pics in which the bridge can be seen, sorry for providing a link rather than a picture.

http://argapa.blogspot.com/2016/01/fitting-tuners-and-stringing-up.html

Cheers / Sven

Sven said:

I've lowered the saddle height on Brükos a few times and I always lost surprisingly much volume. Most of it reappeared when I adjusted the saddle for improved intonation. I can't explain why that happened but it did.

In your case I would use a sharp chisel or a gouge and back that leading edge off as you show in your pics. The result might resemble the one piece bridges I make for my piccolo ukuleles, I'll look for a pic right away.

In this post on my blog there are a couple of pics in which the bridge can be seen, sorry for providing a link rather than a picture.

http://argapa.blogspot.com/2016/01/fitting-tuners-and-stringing-up.html

Cheers / Sven

Click to expand...

I need to get my head around the mechanics of it but I believe that lowering the saddle hieght also reduces the load on the saddle and that that lowering also reduces the load on the bridge and the turning moment on the bridge/saddle assembly applied by the strings. The reduction in those forces reduces excitation of the sound board. A while back I decided to keep actions as high as practical and have seen a Bruko with through bridge stringing.

IIRC string tension is lower with Sopranos than with larger Ukes so perhaps reductions in tension (or rather saddle load) for them is less of an issue. Perhaps one of the reasons that Sopranos turned up to D are thought louder is down to the mechanical effects of higher string tension on the bridge and saddle ????

My thing with tension is that no matter the string height, pressing a string to a fret increases tension. Increased tension means increased pitch. The lower the action the less tension is increased by fretting the string and the less of a pitch increase. So even if the string is perfectly intonated, it will go out of tune to some degree by fretting it. My experience is most can't hear it if the instrument is set up properly, but if the action is unreasonably high of there is severe up-bow in the neck, most can hear it and it does adversely affect their playing.

I try to strike a balance so that I minimize the increased tension at the 12th fret, while not introducing fret buzz and not reducing volume. Unfortunately (or fortunately) I have a very good ear and don't tolerate intonation or pitch problems very well. So for me personally playability and pitch trump volume.

Now of course to achieve the best results the neck has to be perfectly straight, the frets perfectly level, and the string height at the nut optimum. And, in spite of my opinions, some customers just prefer a higher action. I am able to achieve really good results on guitars, but this dang short scale and lack of an adjustable saddle on my Soprano is proving a bit of a challenge!

I'm probably going to have to build a uke to get over it!

Sven, thanks, I may try that. I just think based on fiddling around with that paper clip it's going to be really a challenge to get it dead nuts on. I have a little more wood to take off to get the action down a hair more, which will give me a little more space to work with front to back on the saddle (I've already beveled the back edge of the saddle a bit).

Well I did wind up using Sven's approach (sort of). Worked out great. I was able to get each string intonated with just a couple of passes. Plus, since I had already sanded a bit of a slope on the back of the saddle, this got me to the string height I was looking for.

Maybe not as pretty as the other approaches but was quick, easy, and works for me!

Another plus to this approach is if for some reason this goes south on me I still can do either of the other two options. Oh, and I don't hear any loss of volume.

Thank you all for your suggestions!

Congratulations on what you have achieved and thanks for both sharing your solution and providing a photograph. I’ve found your task an interesting piece of work and now wonder about the original design: perhaps these ‘bridges’ were originally designed to allow just what you have done and that facility either isn’t understood (to be there) or is very rarely used?

If you have time then one or two more photos and a few additional comments on the methods / procedure you used could help future readers. It would be good if, somehow, your ‘fix’ could come to the attention of the Bruko owners on the forum - short of a moderator adding Bruko to the threads’ title I can’t see how that might happen.

Thanks again for sharing.

How it was done

For those who may want to try this, here's what I did. Again, let me just say this is A way - not THE way. There are better ways to do this, but not sure there's an easier quicker way!

The tools are:
1) an Exacto knife with a new #11 blade - sharp!
2) a drafting pencil;
3) a small square;

Starting point - the neck is straight, the frets are level, new strings, approximate action (string height) is set to what you want. I used a straightened paper clip under each string to get an idea where the proper intonation was going to be. Tune it up and hold in a playing position. Play a harmonic at the 12th fret and play the string fretted at the 12th. If fretted and it's a bit sharp then you need to move the clip away from the neck. If flat then toward the neck. In my case they were all a bit sharp. The sharpest was the C string, hence the farther I had to move the clip. There's some pictures of this in the first post. Then measure the distance from the front of the saddle/bridge to the front of the paper clip, or in my case take a picture for later reference.

For these next steps you need a way to firmly clamp the thing. You do not want it moving around while you are carving on it!

I drew a thin pencil line on each side of each string to show me where it rested on the saddle once I removed it. I removed all the strings and chamfered the back side of the saddle. If I ever do this again, I will probably try to save this step to the last. The reason I did it this way is the top of that saddle is about 6 mm wide and flat on top. I wanted to reduce that width before trying to shape the saddle to see if intonation would improve. It didn't.

So now we have each string's position marked and we have a reference point of where the front on the saddle should be for each string to intonate properly. I strung it back up and tuned it. Reason? When you intonate you want all strings to be at pitch in order to have the right tension on the neck. That's also why you check it in the playing position rather than flat on the bench. With guitars, especially electric, that can make a huge difference. With ukes, maybe not so much, but I still do it. Giving away some luthier secrets here!

It's a good idea to tape off under the strings in front of the bridge. Nextly, remove a string. I started with G then C, E, A. It's the same process, just repeated 3 times. I marked a horizontal line between the two string markers at the reference point for proper intonation. I marked a 3 mm gap on the front of the saddle centering on the string markers. Using a #11 sharp blade I carefully cut a vertical slice on each side of the soon-to-be gap angled slightly toward the neck and back to the intonation mark. This is so that when you start slicing horizontally you don't go past your marks and you have a nice clean vertical cut. Use the rear end of the blade so that you don't hit the bridge behind the saddle. If you have some metallic tape you can protect the bridge with that. If you do this place some low-tack tape under the metallic tape. Very carefully I took off small slices left and right starting at the middle of the 3 mm gap up to the mark while holding the blade at the angle I used to cut the vertical side of the gap and just using the tip of the blade. This is where you need to have some skill, patience, can-do attitude, etc, i.e. this is where you can really screw things up! If you've never done this kind of stuff it might be a good idea to practice on something. Just use the tip of the blade, breathe, relax, get rid of any distractions, focus and shave little tiny pieces off at a time.

I stopped just short of my intonation mark, put the string back on (only remove the tail end so it's easy and quick to string back up), tuned it up and checked it. Repeated taking a little more off until it was perfect. 2-3 passes was my experience. YMMV...

Once satisfied with the result I removed the string one more time and sanded the gap lightly with some sandpaper bent over the edge of a popsicle stick. Sorry, didn't show that tool in the pic! If you are good with a knife you may not need this step. I did it anyway although I really didn't take anything measurable off. Just be careful and don't go backwards and change your point of string break (intonation).

Repeat for the next 3 strings as needed. In my case the A string was ok where it was. And of course if you're at the front of the saddle and it needs to move toward the neck, this method isn't going to work. Luckily in my case they all wanted to go toward the back.

So that's it. The whole process took me about 30 minutes. I sleep so much better now. Sadly though it didn't improve my playing, I know it's now properly set up. On to the next excuse...!

Great to hear. That’s a job well done.

Sven said:

Great to hear. That’s a job well done.

Click to expand...

Plus one and thanks for the additional details which I think would make a lot of difference to anyone else attempting the same job.

I wondered how much the strings would, over some months, end up indenting the ‘saddle’ area. However nearly anyone with this type saddle would already know and make any (if any) necessary allowances - can’t see the string height dropping enough to effect anything really but what do I know.

Having got things just perfect with one particular type of string (Aquila Nygluts?) I’m not sure that another brand’s characteristics will be sufficiently the same - some else will know and anyway that’s an issue (or not) for another day.

Thanks again for a great thread, really interesting and helpful.

Regarding string indentation, it's a rosewood bridge/saddle that's been strung up for 20 years. Before I started this I checked for that and didn't see any. I've seen guitars with rosewood saddles and steel strings show this, but not with gut. That would have driven me to cut a slot and make a Corian saddle.

As for other string types or brands affecting intonation, I thought about that too. But that issue, if it happens, would have happened anyway. I put Aquila nylguts on there, a popular and easily available brand, so no intention of trying something else. At this time, that is...!

Thank you all for being a part of this. UU rocks!