Official Luthiers Forum!

Still, 'they' argue....

Must to give up, David.

When Mario and I actually agree on something, you know it has to be
nearly inarguable.   

On slotted pins, the load is right on the edge of the hole, trying to bend
the pin back and slip up in to the hole. When I slot a bridge, the pins can
be pulled out and the strings stay in place. It's like a violin tailpiece. There
is virtually no force pushing on the pin, and no wear on the edge of the
hole.

There are of course still occasionally slotted bridges with damaged plates,
but in my experience they are usually due to use of replacement slotted
pins. Slotted pins (unless you turn them around) on a slotted bridge
are a double whammy, and will kill a plate in no time. The damage is so
predictable and consistent in my experience, that I really don't know how
any repair tech could determine otherwise.

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Eschew obfuscation, espouse elucidation.

You know Todd, having worked in an engineering firm for a few years and having a mechanical technology diploma AND knowing that you are an engineer, I can appreciate that you want some engineering-based answers....

BUT....we both know that not everything needs to be answered in an engineering sense to be viable.

Anyway, I don't have the answers to this but guys like David Collins and Bryan Kimsey who have done a ton or research and documentation on the use of slotted pins and what they tend to do over time do so I'm going to trust them.

Certainly there's exceptions to the rules or generalizations as is noted by your unnamed repair friend.

And for someone with such a bent for engineering, I'm surprised at your statement

[quote=Todd Stock]FWIW, I ramp and slot my bridges as a matter of course, to include recommending it on repair work; however, I don;t see a good engineering-based reason to do it...it just looks cooler.[/quote]

Why would you recommend it on repair work if it has no engineering-based advantage over non-slotted (ramped) bridges. What repairman would ever make money ramping bridges just to make the guitar look cooler

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I was looking back at your drawings Todd (much better than mine btw)
and see a few changes that would help demonstrate my point, and may
even help explain some of our difference thoughts.

First, in the slotted pins notice that the ball end will almost always work a
corner in to the slot, rather than bumping up against the outer diameter
as in your drawing.

[IMG]../forum/useruploads/DavidCollins/2007-09-22_201248_1.jpg[/
IMG]

Look closely at the really bad photo of the bottom of the plate on the top
left. Notice that the one side of the ball end is more than half of it's
diameter over the edge of the hole, if that makes sense. This means that
it is not only the angle the string pulls at the ball end, but the ball end
itself is actually acting as a wedge with the upward pull of the string.

Every small bit the hole wears or the pin dents and bends means that the
ball end moving slightly further in. The ball end them makes contact with
the hole's edge at a steeper angle, or tangent to the circle, and becomes
and even more effective wedge to crush wood and bend the pins.

_________________
Eschew obfuscation, espouse elucidation.

Okay, I'll get Firefox. Here's the photo I tried to post above.

_________________
Eschew obfuscation, espouse elucidation.

Second, bridge slots are generally cut to the width of the double wrap at the
ball end, but deep enough so that the string is not so sharply bent on
exit. Generally if you cut straight down to a good fit at the top of the bridge,
you will be a good enough distance greater at the bottom after considering
the pin's taper. The ball end doesn't push as much against the pin. I will say
that when I pull the pins to demonstrate, the string will often flatten slightly,
but still stay in place when retuned.

_________________
Eschew obfuscation, espouse elucidation.

Oh, I should add a disclaimer that I certainly had my share of sour
experiences with engineers as a machinist. Always having to redesign parts
when they moved from the abstract of a drafting table, to the real world of
metal and tools.

When I worked for Comau, the folks in charge made all the engineers
working on our line come down to the floor for a week to actually make the
parts they had designed, then try to put them all together. It was quite a
wake up call for many of them moving from the abstract to the tangible, and
finding a lot of things in practice that were never anticipated on the drawing
board. Not that I hold a grudge against engineers or anything though..... just
the ones that I've worked with.

_________________
Eschew obfuscation, espouse elucidation.

Somewhere in the past, I earned a piece of paper that still hangs on my wall here in the office. It says engineer.... Now I wear a luthier's hat, but....... I give up. In the other thread, we have a fella who is measuring a string ball at an angle to show it is smaller than it is, never mind that a tapered hole is a tapered hole, and the bottom side will not be sloppy as long as the entire length is reamed. Ad here we demand textbook engineering terms? I give up.

Mario, chill.

Tomorrow the sun will come up.

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