Using an Acoustic Guitar Bridge Pin Hole Slotting Saw to make deeper slots - is this recommended?

ToneControl · March 2022

Is this a good idea?

bertie · March 2022

my 10 penneth - sometimes for when you lower/shave the saddle but not if the guitar doesnt need it - the problem arises if/when you want a higher action and put a taller saddle back in - the angle may be too acute

Tannin · March 2022

Bertie has nailed it.

Andyjr1515 · April 2022

If there is insufficient break angle over the saddle and it is not practical or possible to remove the neck and increase the heel angle to allow a higher saddle to be used, this method can transform the sound.

But if the break angle is already OK, then little or no benefit.

Lewy · April 2022

Break angle only really needs to be sufficient to stop the string moving around on the saddle. Beyond that what matters most is the height of the string above the soundboard. It’s a question of torque.

Mellish · April 2022

^^^ that's very true

bertie · April 2022

Lewy said:

Break angle only really needs to be sufficient to stop the string moving around on the saddle. Beyond that what matters most is the height of the string above the soundboard. It’s a question of torque.

but surely the break angle contributes "something" to the "torque" , tighter break angle = more pressure on the saddle ? or more importantly the opposite ?

Purely "string height" would be affected by the thickness of the bridge ?

BigPaulie · April 2022

bertie said:

Lewy said:

Break angle only really needs to be sufficient to stop the string moving around on the saddle. Beyond that what matters most is the height of the string above the soundboard. It’s a question of torque.

but surely the break angle contributes "something" to the "torque" , tighter break angle = more pressure on the saddle ? or more importantly the opposite ?

Purely "string height" would be affected by the thickness of the bridge ?

I agree. I don't see how string height above the soundboard alone could dictate torque. What about bridges such as those on Takamines and Lowdens where the string doesn't pass through the bridge/top/bridge plate?

Mellish · April 2022

If I look at my HD-28, there's very little break angle at the bridge, just enough to prevent string slip sideways across the saddle. Tonally, it's great and loud as you like. OK, some of that will be the forward shifted bracing. But does it suffer through lack of break angle? I don't think so

TheMadMick · April 2022

Lewy said:

Break angle only really needs to be sufficient to stop the string moving around on the saddle. Beyond that what matters most is the height of the string above the soundboard. It’s a question of torque.

Torque is the turning moment around a point. So, if the break angle is small so is the turning moment because the distance from the fulcrum - the point where the string departs company from the bridge - is small due to the low break angle. If you slot as proposed, then the distance where the string parts company from the bridge is increased and so the turning moment increases. Thus torque increases.

Turning moment = force x distance.

The torque or turning moment can be resolved into two components. First, that onto the saddle and hence on the bridge and top of the guitar. That is what we are concerned with here. The other component is the string tension at right angles to the saddle. (that's not completely accurate but good enough to be getting on with).

Hope this helps?

BigPaulie · April 2022

TheMadMick said:

Lewy said:

Break angle only really needs to be sufficient to stop the string moving around on the saddle. Beyond that what matters most is the height of the string above the soundboard. It’s a question of torque.

Torque is the turning moment around a point. So, if the break angle is small so is the turning moment because the distance from the fulcrum - the point where the string departs company from the bridge - is small due to the low break angle. If you slot as proposed, then the distance where the string parts company from the bridge is increased and so the turning moment increases. Thus torque increases.

Turning moment = force x distance.

The torque or turning moment can be resolved into two components. First, that onto the saddle and hence on the bridge and top of the guitar. That is what we are concerned with here. The other component is the string tension at right angles to the saddle. (that's not completely accurate but good enough to be getting on with).

Hope this helps?

I always viewed the saddle top as the fulcrum and the point where the string parts company with the bridge as the effective point of force application. Hence my perception that whatever happens past that point is inconsequential.

bertie · April 2022

head implosion

ToneControl · April 2022

some discussion here:
Break Angle at the Saddle - Australian/New Zealand Luthiers Forum (anzlf.com)

Lewy · April 2022

I went down this rabbit hole a few years ago on the AGF and UMGF and what I gathered from all of that was essentially that once the downward force on the saddle is "enough" then there's no more to be gained from making it steeper. And "enough" is less than you might think. Someone with too much time on their hands built a whole rig to test it all (Alan someone?). By far the greater impact on projection and tone comes from the height of the strings off the soundboard. From recollection that's because there are actually two components to the energy transfer from the string...the transverse motion and the tension change. One matters loads more than the other and that's the one dictated by string height off the soundboard, not pure downward pressure on the saddle. Or something like that.

Either way, people don't tend to think about string height too much because the things you do to increase break angle (such as raising the saddle) also raise the string height. So they think it's down to the break angle, or they think it's down to raising the action, but really it's not. It's down to total string height. Assuming the break angle is "enough".

BillDL · April 2022

When a string breaks over a sharp fulcrum or departs the ledge of a nut there is always going to be a tiny length of that string before it begins vibrating. The thicker the string the further away from the fulcrum the point will be the place where the string begins to vibrate freely. Thin unwound strings will begin the vibrate almost immediately they leave the breakover point. For practical purposes an all leather bull whip made from decreasing thickness from handle to tip demonstrates this quite well as it becomes more flexible the thinner it gets.

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Using an Acoustic Guitar Bridge Pin Hole Slotting Saw to make deeper slots - is this recommended?

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