Shimming up a reso bridge?

[alexkirtley]

My MM blues '28 prototype is a wonderful thing but I have had some trouble setting it up, I am not using it for slide, just fingerstyle however the action is too low despite the fact when I made the bridge I left it as high as it would go, has anyone ever shimmed up the entire biscuit to raise the bridge?

[snakehips]

Hi Alex !

Is the action too low with one of the NRP biscuits I sold you ?

Did you cut the saddle too low ? If so, better to start again with a new one.

OR is the action too low without even having reduced the height of the saddle, just got shallow string slots ?
The NRP biscuits have a VERY tall saddle so I am struggling to imagine that this it is not high enough ???
If a NRP biscuit's bridge is not tall enough, the either the cone is sinking down (collapsing) or the geometery of that guitar (neck angle etc) is all wrong.

As for shimming the saddle/bridge, it seems a heck of a lot of trouble and difficult to do well.
The saddle is glued into a slot cut into the biscuit.
I'd roughly estimate that this slot is only 3-4mm deep.
If you shim the saddle from underneath, then mostly only the shim will be in the slot and the saddle above will only be retained by the strength of the glue you use to bond it to the shim. The saddle needs the slot to prevent tilting of the saddle.
Plus, if you take out the saddle and glue a shim on the underside of the saddle, you are assuming that :
1. You can get the saddle off the biscuit cleanly (without it all breaking up into splinters
2. You can sand PERFECTLY FLAT the base and sides of the slot, clear of old glue (and without widening the slot in the process)
3. You can sand the top and bottom of the shim perfectly flat
4. You can sand the underside of the shim perfectly flat
All the pieces need to fit together perfectly, without gaps, otherwise they will rock back and forth on each other and/or have poor tone.

Post a close-up photo of the saddle, strung up without the coverplate on, so we can get an idea of your set-up so far.

[Deleted]

Shimming up the entire biscuit is not a good idea.
Has anyone tried it? Probably...(but not me).
Usually, a tiny screwdriver tapped into the glued area lightly will 'snap' the saddle free from the biscuit - or wreck it.
I have used matches for shims, glued with superglue, and cleaned up with a bit of sandpaper.
Works for me! ymvmv
TT

[snakehips]

Whoops !

Looks like I misread Alex's post !!
Shimming the entire biscuit won't be as good as you think it might, I'd expect.

Whatever extra height you need at the 12th fret, you need to double that height to tell you how thick a shim you need (as a minimum).

Potentially, you need a disc of maple, circa 1-2mm thick.
Remember this disc needs to be perfectly flat on both sides of a thin disc of wood.

Do you have the appropriate machinery to do this ?
I could manage that - but I only have a standard metal file and hacksaws etc.
Sure, you could hold the disc and grind it continuously on a large flat sheet of sandpaper, laid on a very flat surface, to get it flat BUT holding a 2mm thick piece of wooden disc in your hands perfectly parallel with you flat table surface while grinding is NOT easy.
Adding a shim under the biscuit will obviously make the biscuit thicker and heavier - and this may affect tone.
As far as I remember, single cone guitars work best when the cone and biscuit are as light as possible.

I highly recommend you start with a new biscuit unless a brand new, uncut NRP biscuit is not tall enough.
If it's not tall enough (and it should be, as NRP saddles are often WAY too high to start with), you need a luthier to look at that guitar.
I usually need to cut nearly half the height of the saddles of a NRP saddle, when I have installed new biscuits (I've done at least 10).

[Michael Messer]

Hi Alex,

Just a quick comment here....

You could also consider raising the cone by fitting a some laminate to the sound well. This would allow you to lower the bridge which is improves the tone.

Shine On
Michael

[slide496]

Might it help to know, reading the thread, where on the fretboard alexkirtley has trouble with the action being too low when playing fingerstyle? In first position chords or the entire fretboard?

Harriet

[alexkirtley]

The NRP bridge was left as high as could possibly be yet the action is too low (at the 12th fret), I have some thin pieces of oak which were originally going to be used for a guitar build (An ambitious project which was very soon scrapped), it should work perfectly for this purpose, I'll give it a shot
 

[alexkirtley]

The operation was successful, I sacrificed a previous bridge attempt to turn it into a shim but it now plays wonderfully.



However, I different problem has arisen, since the saddle is now very high in order to get the action right, the hand rest on the cover plate is too low so the strings touch the underside of the hand rest, I don't know if I can get cover plates with higher hand rests or not or if I can modify the current one somehow

[gaucho]

It's very strange that you need the saddle that tall to play fretted. Forgive me if this was already addressed earlier in the thread but are you sure the neck angle is correct? Is that the stock Continental cone or a NRP (I believe there is a height difference in the cones)? I've never see a reso that was properly set up for fretted play that was close to hitting the underside of the hand rest. If it's a Hot Rod cone, you might try using the original Conti cone and see if that is better. I've swapped out numerous Conti cones for Hot Rods and the sound difference wasn't really that great.

[zak71]

Jan 28, 2015 2:03:40 GMT gaucho said:

I've never see a reso that was properly set up for fretted play that was close to hitting the underside of the hand rest.

I have...on an old Style O that an amateur had reset the neck on himself...and overshot the angle by a few degrees.

That's definitely a Continental cone - the spirals don't reach its apex.

I'd be concerned that doubling the amount of wood between the strings and the cone and increasing the mass of the biscuit would have a perceivable adverse effect on the sound.

Although the proper way to correct this issue would be a neck reset, considering that this is a wood bodied guitar, the simpler solution would be to add a layer of wood lamination underneath the cone as suggested earlier by Michael. If done correctly, it should have no adverse effects on the guitar's sound.

[alexkirtley]

I don't know if the neck angle is right, it is a prototype model so it may or may not be.

I would put wood under the cone but I don't have the tools to accurately cut out a piece to fit so what I've done now will have to do until I am able to do that, I got a very good deal on this guitar from Michael, and it is a prototype model so I'm not going to be picky over it and I don't expect perfection. I'll expect that when I(hopefully) one day buy a national

[Stevie]

I changed my MMB biscuit for an NRP one. The NRP saddle was too low. I made a replacement saddle from some Canadian hard rock maple that a colleague who was building a banjo let me have. I linished it into shape. This worked fine and there was no detectable difference. That means that from my perspective, the exercise was a waste of time and at the end of the day, it's only half of an NRP biscuit / saddle assembly now anyway. With the benefit of hindsight I would have left it alone. I noted that the strings did indeed touch the handrest, but once up to pitch with the tension on the neck and the cone compressed a little, all was fine.

e&oe

[snakehips]

Hi again !

I take it that Alex has the string height where he wants it ?

Assuming that is correct BUT the strings are touching the underside of the coverplate handrest, I fail completely to see how putting a layer of wood on the well to raise that up, to go back to using a regular biscuit, is going to help ?
If he does all that and brings it back to the same string height/action he wants it, the coverplate handrest will still contact the strings !!!!

I think it sounds very much like it needs a neck reset to get it to the correct angle otherwise it is never going to be worth whatever he did pay for the guitar.
Was it not just a "cosmetic prototype" ?

I am assuming though that the action height Alex wants the guitar at is not some over-the-top un-natural height, causing the problem.

What is the action at the 12th fret ?
(Top of fret to underside of string)

[Michael Messer]

Hi Alex,

Be careful that you don't dig yourself into a deeper and deeper hole with so much varied advice.

I am a little confused about this because the guitar is not 'cosmetic prototype' (what would be the point) and when I first received it I played it and it was fine.
It is really difficult to advise you without seeing the guitar, but I still think that two semi circles of plywood to raise the soundwell would have done it.

Here are some photos of the guitar with strings on. These were taken in China at the home of MM Guitars factory owner.

I am showing these pics to prove that it did have strings and it did play fine.

I am baffled, but from a distance it is really hard to advise.





Shine On
Michael

[alexkirtley]

The guitar with a regular saddle is playable, I still have the most recent saddle I made, the current arrangement is a combination of the flailed first and second attempts at making a bridge, however with the normal saddle the action was about 1-1.5mm, the result of this was that when playing with picks it would have fret buzz and slide was not really possible, with the current arrangement it has an action of about 2.5mm-3mm and it plays clearly and sounds good to me (playing without the coverplate on), when I get home from college I'll mess around with it to see if I can get it right, it is not far off, there is nothing wrong with the actual guitar, it doesn't need a neck reset, this is all just a case of getting the right set up for me which at the moment is a case of trial and error
I have the regular bridge so I can resort back to how I had it set before if needed