Bridges..How to?

[gratay]

I'm about to bombard you all with various questions regarding bridges ..I am nearing this stage and need to research ..and what better place than here.

My main concern is intonation...I don't want it to be close ..I want it to be spot on. Which leads me to think maybe cutting the saddle slot after the bridge is glued on might be more accurate for intonation..(although I don't really want to shell out the coin for a stewmac saddle slotting jig )even though it looks good.
Or maybe locate the bridge position ( maybe screw it in tempoarily and use something like stew-macs intonator) and remove bridge and cut the slot with a homemade jig prior to gluing on.

How do you guys do it?

And also , do you apply the finish first and then glue the bridge or finish after the bridge is on..
I'm planning on doing a french polish type finish by hand with maybe U-beaut hard shellac.

cheers guys and I'll apologise now for the amount of questions that will follow.
cheers Grant

[graham mcdonald]

Hello Grant,

First thing to remember is that guitars do not play in tune. The frets are an average, and unless you want to have a different fretboard for each key you play in (as was sold some years ago) you just have to deal with that and not stress out too much about it.

Adding compensation helps, and using a 5mm (3/16") wide saddle helps even more. Cut the saddle slot at the usual angle and glue the bridge in place with the front of the saddle at the top e string position 2mm further back than the theoretical scale length. Jim Williams' book has a very efficient way of setting the contact points along the length of the saddle using bits of cut-off b string and a good tuner. The usual 3/32" saddle is not really wide enough to get accurate intonation on a steel string guitar.

Remember as well that all you are doing is setting the intonation at the 12th fret and that does not necessarily mean accurate intonation at the rest of them. There are those who use the Buzz Feiten (spelling?) nut compensation as well.

Just keep in mind there are lots of very good guitarists out there who make very good music on instruments that theoretically don't play in tune. It doesn't bother them or their audiences. Many good guitarists go through a period of frustration with 'out-of-tuneness' and then get past it and just make music

I finish the soundboard before gluing the bridge, mostly because it makes cutting and polishing a lot easier

Good luck with the guitar and keep us posted

cheers

graham

[kiwigeo]

I finish first and then scrape away finish under bridge before gluing on same.

I have been routing my saddle slot on the bridge blank before shaping and fitting same. The last guitar had bad intonation due to bridge ending up slightly off location so on the next guitar Ill be routing slot after I fix the bridge.

Like Graham said the guitar is a compromise in terms of "being in tune". A good guitarist can compensate for most of the built in inaccuracies of the average guitar. One can argue that a perfect sounding guitar wouldnt sound right...a bit like the old solid state versus valve sound argument.

Williams's bridge positioning method is one of the easiest Ive come across.

Cheers Martin

[Hippety Hop]

If you can hook a temporary tailpiece to the tail end of your guitar without screwing or clamping it, then string it up and use a floating bridge to find the exact saddle position. Sounds easy.

[Bob Connor]

I got one of these from Stewmac Grant, but you could easily make up something simpler and cheaper - like a piece of wire or a very small allen key to check the intonation before you rout the slot.

[kiwigeo]

First we had THE PHANTOM!!!!

..........now we have THE INTONATOR!!!!

[Allen]

I've been cutting the slot in the bridge prior to shaping it. I use the Ibex fret scale rule to give me the length for the high E and using Luthier Supplies center line finder with bridge locator to place it.

Also I'd finish before gluing down. It'll make finishing sooooo much easier. You could locate the bridge prior to finishing. Even drilling a couple of holes through the outside pins, just to make it simple to locate once you have your finish on. It's also possible to mask off the area of the bridge footprint so you don.t have to scrape the finish back. I've done it both ways, and kind of prefer masking it off prior to finish.

TIP: To make a masking template of the exact shape of your bridge, lay down some strips of masking tape on a smooth hard surface like glass or marble. Make sure that they overlap if you are using narrow tape. I like to use 2" wide tape so I only need 1 piece. Lay your bridge over the tape and use a razor blade to cut the tape following the outline of the bridge. I usually then cut the mask just a hair smaller than the bridge by eye. Apply to top in correct position and apply your finish. You will need to use a very sharp blade to score the finish in order to peel the masking tape off.

[Bob Connor]

If you cut the slot before you glue the bridge to the top you are doing it by "guessometrics".

If you are serious about getting the intonation right you will cut the slot after the bridge is glued to the top.

[Dave White]

If you cut the slot before you glue the bridge to the top you are doing it by "guessometrics".

If you are serious about getting the intonation right you will cut the slot after the bridge is glued to the top.

Not necessarily Bob. I'm very serious about getting the intonation right - so much so that I do split saddles and have different rake angles for different designs (travel to britone) and have appropriate variants in my slotting jig, I find it easier to slot them off the guitar and then radius the bottom to match the tops arch, then make the bridge and then position on the guitar with neck fitted and bolted on the prefinished top, clamp the bridge and then drill and ream the two outside bridge pin holes for the plastic tapered pins that will hold it there for gluing. No guessometrics in terms of measuring as with the nut fitted roughly and marked I can measure each string length individually. Using a 3mm wide saddle and split saddle this way usually gives me spot on intonation on each string along the middle of each of the split saddles, and if not quite there is more than enough wriggle room.

Given that my bridges are curved side to side and front to back I would have more trouble making an appropriate slotting jig for doing it on the top and it would scare the bejesus out of me too - coward luthier

Horses for courses I think.

[gratay]

thanks for all your feedback....plenty of great insight to digest.

Graham ,...thanks for the advice on the wider saddle ,.That makes a heap of sense to me.
As far as playing in tune goes, I've always thought an acoustic guitar with individual adjustable saddles would be a great idea..Maybe not athstetically.. I know some makers like Gibson have done models with saddle height adjustment but I've not seen any that I can think of that are adjustable for intonation?

Martin,....second time Jim Williams gets a mention in the first 2 posts...I really have to get a copy of that book..

Hippety,...I have seen a pic of that sort of jig..on one of the forums ..I'm definitely going to look more into that one.

Allan,...thanks for the masking off tip...and I was eyeing off that luthiers supply jig which looks like a seriously nice bit of kit for locating the bridge.

And Bob,...the guessometrics factor is my main concern and the reason for this topic..I've no doubt its the way to go.

Has anyone made up their own jig to cut the saddle slot after the bridge has been attached? again the stewmac one looks very nice..but I'm sure all you need is something simple with a fence for a laminate trimmer

Thanks again,
Grant

[gratay]

If you cut the slot before you glue the bridge to the top you are doing it by "guessometrics".

If you are serious about getting the intonation right you will cut the slot after the bridge is glued to the top.

Given that my bridges are curved side to side and back to back I would have more trouble making an appropriate slotting jig for doing it on the top and it would scare the bejesus out of me too - coward luthier

Horses for courses I think.

Now your scaring the bejesus out of me, Dave.
If it was a true flat-top would be not as much drama I'd imagine.but on these domed tops?.
me will ponder some more on all this.
Cheers Grant

[Taffy Evans]

Hi Grant I'm late in again but I'll post it any way...


I have used all the methods mentioned above and possibly some that have not. Here are a couple of photos.

Show’s my â€

[graham mcdonald]

If you cut the slot before you glue the bridge to the top you are doing it by "guessometrics".

If you are serious about getting the intonation right you will cut the slot after the bridge is glued to the top.
_________________
Bob, Geelong

I can't see how it can be any more inaccurate to glue a preslotted bridge in place, than it would be to glue an unslotted bridge and then slot it. The front of the bridge slot is always going to be a certain distance from the nut which is not really going to change. I suppose there might be arguments about action height and string gauges affecting the amount of compensation, but I would think it very risky to establish a bridge position for anything else but an average action and string gauge. Once you have done it right once and know the position in relation to your scale length, what is going to change? I always think I should make up a jig that will fit in the nut slot and the saddle slot, but I have never got around to it. In any case I have been using the bridge position marks on an Ibex scale ruler for 25 years and it works just fine.

The other thing to think about is that it is a lot easier to slot and drill a bridge when it is a rectangular piece of timber rather than trying to do it with a jig clamped on a domed soundboard.

cheers

graham

[Colin S]

I too pre-slot my bridges, indeed on my lutes I glue the bridge onto the top before I glue the top to the body! I don't believe guess work comes into it at all and with a 1/8" saddle, there is plenty of meat for fine tuning, I'm very fussy about intonation, though final intonation comes from the player.

I also glue my bridges on before finishing the top of the guitar, this is common practice among a lot of classical builders, but I also do it for my steel strings as I like to play then for a couple of weeks befoe finishing the top. The top thickness, especially in the lower bout gets some tweeking after its strung up and played, again commen practice mong classical builders. French polishing is no problem with the bridge in place.

Colin

[Bob Connor]

I can't see how you can get it any more accurate than doing it with the bridge atached to the guitar and with the strings at the height that you they will ultimately end up at, and with the gauge of string that the guitar has been built for.

[gratay]

Thanks for the pics Taffy...In the pic of your intonator jig I'm just wondering what the bolt at the back of the jig is for? Is that a stop bar that contacts the back of your bridge?

Colin , that sounds like a great idea to be able to further tune the top prior to finishing...thats certainly food for thought.

cheers grant

[Dave White]

I can't see how you can get it any more accurate than doing it with the bridge atached to the guitar and with the strings at the height that you they will ultimately end up at, and with the gauge of string that the guitar has been built for.

If you get the pre-slotted bridge saddle to be covering the right area then the process of using an "intonator" (at its simplest some offcuts of treble strings) to mark where you need to shape the saddle is exactly the same (with your saddle height and chosen gauge of strings on) as if you slot with the bridge on the guitar. You'll get exactly the same result. The precision is in pre-slotting in the right place and gluing the bridge in the right place - this can be done with monotonous consistency.

The idea of having to seperately shape and intonate saddles for going from say light to medium strings (or from say standard tuning to DADGAD with the same gauge of strings) is a puzzle to me by the way.

[gratay]

I'm thinking of going with unslotted bridge pins..
The ones Stewmac sell all seem to be 5 degree taper.

Does anyone know of any supplier in Australia that sells a
5 degree tapered reamer.?

Cheers Grant

[gratay]

I'm just wondering how thick you like your bridge to be?

after I glued my fingerboard on and radiused I laid a straight edge down the centre and my measurement at the saddle is 0.3" (7.7mm) from the face to the straightedge minus the frets.

I'm just wondering how thick to make my bridge? Would it be optimum to add the height of the fret to the 7.7mm and make my bridge that thickness so the straightedge sits right on top of the bridge when the fretboard is fretted.?

I lost 1mm at the saddle when gluing up...either a product of clamping or water content in titebond...who knows?..

its a pretty dense ebony bridge blank I have so maybe slightly thinner bridge may be fine but it is a cedar face ..

warning :- this thread regurgitates from time to time

cheers Grant.

[Dave White]

Grant,

It depends on what you want the saddle height/string height from soundboard to be and what action you want. Basically if you add on your fret height, plus twice the action you want the strings to be at the 12th fret in the middle of the fretboard plus the amount your neck "shifts" under full string tension, then that's where the top of the saddle in the middle will be. Take off your desired saddle height above the bridge and you have your bridge height in the middle.

[graham mcdonald]

Generally bridge shouldn't be more than 10mm thick in the middle and no less than 8mm.

A straight edge sitting along the middle of the frets should just clear (<1mm) the top of the centre of the bridge. Preferably, the shape of the top of the bridge should follow the radius of the finger board, so there is an even height - around 3mm - of saddle above the bridge.

As Dave points out there is often a bit of a shift when string tension is applied, so that might have to be taken into consideration

cheers

graham

[kiwigeo]

My bridges usually work out at 9-10mm. Getting over 10mm is a bit on the thick side on my steel strings.

Actual bridge height should be calculated by laying a straight edge along fingerboard (unfretted) and calculating bridge thickness with allowance for fret height and action.

[Bob Connor]

C.F. Martin specify half an inch string height from the soundboard for their guitars.

[jeffhigh]

C.F. Martin specify half an inch string height from the fingerboard for their guitars.

Gee Bob, I hope you mean 1/2" from the Soundboard, would hate to be playing with strings that high

[Bob Connor]

I did Jeff. . I'd better edit that.