Slotting a bridge

[redir]

Again, I've never seen bridge plates damage to any guitar that was due to slotting Bridges. Granted there are far fewer guitars with this procedure done so it may not be a fair comparison but I've seen plenty of bridge plates damage due to the ball end string forcing it's way up the pin holes that would not have happened if it was slotted.

[JonWint]

Originally Posted by jonfields45

When you cut a slot in a bridge plate you interrupt strong continuous grain. It makes no sense to me to do that and that must be something all the big guitar manufacturers also figured out.

Now I don't doubt a long list of boutique builders disagree, but the vast volume manufacturers seem to have found something they agree on.

It took Martin 159 years to stop slotting pin holes. They've been non-slotted for 28 years.

They probably didn't consider the slotting to be a detrimental practice.

[charles Tauber]

Originally Posted by jonfields45

I live near the Martin factory and with business connections here in the Lehigh Valley have had the opportunity to spend time with Dick Boak and Chris Martin. With the tooling they have to make guitars they don't need to compromise design to save money on unassisted hand work.

I'd really like to understand Martin's use of non tapered holes with tapered pins. If we assume your assertion is valid, it is not being done to save money, why is it that Martin used to taper the holes of all bridge pin holes and now does not? Did Martin discover some previously unknown principle of mechanical design that eliminates using a tapered pin in a tapered hole? Have they similarly eliminated the use of tapered end pin holes for use with tapered end pins?

Why is it that virtually every other guitar maker, large and small, matches the taper of hole to pin? Are all but Martin deluded and wasting their time?

In no other mechanical application can I find a tapered pin used in a straight hole. Doing so appears to defeat the purpose of using a tapered pin.

Since you have the ear of Mr. Boak and Mr. Martin, why haven't they simply eliminated using tapered bridge (and end) pins, since they eliminated the taper in the hole?

And to some extent we do a disservice promoting potentially destructive modifications.

Originally Posted by phavriluk

Now, I think guitar consumers shouldn't be taking saws and files to their bridges without a well-founded idea that they know what they're doing.

You both raise a valid point: should we, collectively, be providing guitar owners with information on how to achieve whatever modifications they want to make to their guitars?

Where does one draw the line? Should we provide no information of any kind - including some things that are relatively accessible to the average player, such as how to adjust truss rods, slot nuts, file saddles ... - or provide an environment where information, of all kinds, flows freely?

Originally Posted by redir

Again, I've never seen bridge plates damage to any guitar that was due to slotting Bridges. Granted there are far fewer guitars with this procedure done so it may not be a fair comparison but I've seen plenty of bridge plates damage due to the ball end string forcing it's way up the pin holes that would not have happened if it was slotted.

Ditto. I've never seen a guitar damaged by properly slotted bridge pin holes.

Where is the evidence to the contrary? There is lots of evidence to support that not slotting the pin holes - and using soft plastic pins - does lead to damage.

[Peter Wilcox]

So, has anyone seen damaged Martin bridge plates due to non-slotted non-tapered holes?

[jonfields45]

Originally Posted by charles Tauber

I'd really like to understand Martin's use of non tapered holes with tapered pins. If we assume your assertion is valid, it is not being done to save money, why is it that Martin used to taper the holes of all bridge pin holes and now does not? Did Martin discover some previously unknown principle of mechanical design that eliminates using a tapered pin in a tapered hole? Have they similarly eliminated the use of tapered end pin holes for use with tapered end pins?

Getting back to slotting and 159 years of experience. One reason slotted pins became the preferred solution was there was finally the technology to mold hard plastic and ceramics (Tusq), or CNC bone and wood, to economically make this new wonder.

In my experience as a guitar owner with a mirror, string balls do tend to pull into and wear the slot in slotted bridge pin holes.

I suspect tapered pins in an untapered hole, might have some advantages that making a few hundred thousand guitars a year might highlight. Maybe stuck pins is a bigger problem for most owners.

If you've toured that factory, unassisted hand work is something only applied to the most expensive models. If they wanted to taper the bridge pin holes, they would and it would cost them nothing.

[John Arnold]

So, has anyone seen damaged Martin bridge plates due to non-slotted non-tapered holes?

Yes. I have seen damaged bridgeplates on Martins that are only a few years old. The use of slotted thermoplastic bridgepins always risks damaged pins, and damaged bridgeplates.
Martin stopped tapering the holes for one reason....to save time and money. Tapering means using a reamer, which is an extra step done after the holes are drilled.
FYI, Martin stopped slotting bridges in the 1980's for the same reason....saving money.
The untapered holes are not perfectly straight; they are step-drilled. The hole in the bridge is slightly larger than the drill used to complete the hole through the top and bridgeplate.
The pin holes on most Martin models are not quite large enough to fully seat the pins, and that adds to the risk of bridgeplate wear. A pin that is not fully seated is smaller where it exits the bridgeplate, so it is an even looser fit where the fit is critical....where the string ball is pressing on it. That is why it is recommended that those guitars have the pin holes reamed with a proper 5 degree reamer (fully seating the pins) as soon as possible.

In my experience as a guitar owner with a mirror, string balls do tend to pull into and wear the slot in slotted bridge pin holes.

My experience is 35 years as a full-time guitar repairman, mostly on vintage Martins with slotted bridges. I have ample evidence that using unslotted pins is superior when it comes to bridgeplate wear. I have witnessed many, many examples of prewar Martins with their original unslotted pins, and minimal bridgeplate damage. That is virtually an impossibility with slotted pins.
I see relatively few problems from slotting the bridges that are not traced to using inferior slotted pins, or sloppy slotting jobs. Yes, you heard right. Martin slotted bridges and used slotted thermoplastic pins from the mid-1940's until the late 1980's. The 'high tech' slotted pins in common use on US made guitars in that period had a shallow slot that would not clear the largest strings. So Martin continued slotting bridges until the late-1980's.
I remember when Martin historian Mike Longworth told me that they had changed to bridgepins with deeper slots, so that they no longer had to slot the bridges. I responded by saying, 'you went the wrong way'. He didn't understand, but by that time, I already had spent several years repairing bridgeplates and buying unslotted ebony pins from Europe.
Unslotted pins are superior, for several reasons:
1) unslotted pins are stronger and more durable
2) with unslotted pins, the string ball rests on a solid surface, and they can be rotated, so that the bearing surface changes each time they are inserted.
3) with slotted pins, the string ball rests aganst the same area every time, putting more stress on a weaker pin.
4) with slotted pins, the string ball presses against two knife edges, which are very delicate. Slotted pins (especially the cheap thermoplastic variety) will show wear in this area relatively quickly...often even before the owner realizes there is a problem. Unslotted pins can (and often do) last forever.
5) with slotted pins, the string at the ball is bent at a sharper angle, putting more force on the pin than it does with a slotted bridge. More force on a weaker pin means more damage to the pin, which will result in bridgeplate damage.
6) (very important distinction) Slotting the bridge allows the slots to be sized for each individual string. With slotted pins, the slots are large enough for the 6th string, which means a sloppy fit on the other five. Sloppy fit is asking for bridgeplate damage.

[JayBee1404]

Originally Posted by John Arnold

Yes. I have seen damaged bridgeplates on Martins that are only a few years old. The use of slotted thermoplastic bridgepins always risks damaged pins, and damaged bridgeplates.
Martin stopped tapering the holes for one reason....to save time and money. Tapering means using a reamer, which is an extra step done after the holes are drilled.
FYI, Martin stopped slotting bridges in the 1980's for the same reason....saving money.
The untapered holes are not perfectly straight; they are step-drilled. The hole in the bridge is slightly larger than the drill used to complete the hole through the top and bridgeplate.
The pin holes on most Martin models are not quite large enough to fully seat the pins, and that adds to the risk of bridgeplate wear. A pin that is not fully seated is smaller where it exits the bridgeplate, so it is an even looser fit where the fit is critical....where the string ball is pressing on it. That is why it is recommended that those guitars have the pin holes reamed with a proper 5 degree reamer (fully seating the pins) as soon as possible.

My experience is 35 years as a full-time guitar repairman, mostly on vintage Martins with slotted bridges. I have ample evidence that using unslotted pins is superior when it comes to bridgeplate wear. I have witnessed many, many examples of prewar Martins with their original unslotted pins, and minimal bridgeplate damage. That is virtually an impossibility with slotted pins.
I see relatively few problems from slotting the bridges that are not traced to using inferior slotted pins, or sloppy slotting jobs. Yes, you heard right. Martin slotted bridges and used slotted thermoplastic pins from the mid-1940's until the late 1980's. The 'high tech' slotted pins in common use on US made guitars in that period had a shallow slot that would not clear the largest strings. So Martin continued slotting bridges until the late-1980's.
I remember when Martin historian Mike Longworth told me that they had changed to bridgepins with deeper slots, so that they no longer had to slot the bridges. I responded by saying, 'you went the wrong way'. He didn't understand, but by that time, I already had spent several years repairing bridgeplates and buying unslotted ebony pins from Europe.
Unslotted pins are superior, for several reasons:
1) unslotted pins are stronger and more durable
2) with unslotted pins, the string ball rests on a solid surface, and they can be rotated, so that the bearing surface changes each time they are inserted.
3) with slotted pins, the string ball rests aganst the same area every time, putting more stress on a weaker pin.
4) with slotted pins, the string ball presses against two knife edges, which are very delicate. Slotted pins (especially the cheap thermoplastic variety) will show wear in this area relatively quickly...often even before the owner realizes there is a problem. Unslotted pins can (and often do) last forever.
5) with slotted pins, the string at the ball is bent at a sharper angle, putting more force on the pin than it does with a slotted bridge. More force on a weaker pin means more damage to the pin, which will result in bridgeplate damage.
6) (very important distinction) Slotting the bridge allows the slots to be sized for each individual string. With slotted pins, the slots are large enough for the 6th string, which means a sloppy fit on the other five. Sloppy fit is asking for bridgeplate damage.

Now THAT’S what I call a great, knowledgeable post!

[jonfields45]

Originally Posted by John Arnold

Yes. I have seen damaged bridgeplates on Martins that are only a few years old. The use of slotted thermoplastic bridgepins always risks damaged pins, and damaged bridgeplates.
Martin stopped tapering the holes for one reason....to save time and money. Tapering means using a reamer, which is an extra step done after the holes are drilled.
FYI, Martin stopped slotting bridges in the 1980's for the same reason....saving money.
The untapered holes are not perfectly straight; they are step-drilled. The hole in the bridge is slightly larger than the drill used to complete the hole through the top and bridgeplate.
The pin holes on most Martin models are not quite large enough to fully seat the pins, and that adds to the risk of bridgeplate wear. A pin that is not fully seated is smaller where it exits the bridgeplate, so it is an even looser fit where the fit is critical....where the string ball is pressing on it. That is why it is recommended that those guitars have the pin holes reamed with a proper 5 degree reamer (fully seating the pins) as soon as possible.

My experience is 35 years as a full-time guitar repairman, mostly on vintage Martins with slotted bridges. I have ample evidence that using unslotted pins is superior when it comes to bridgeplate wear. I have witnessed many, many examples of prewar Martins with their original unslotted pins, and minimal bridgeplate damage. That is virtually an impossibility with slotted pins.
I see relatively few problems from slotting the bridges that are not traced to using inferior slotted pins, or sloppy slotting jobs. Yes, you heard right. Martin slotted bridges and used slotted thermoplastic pins from the mid-1940's until the late 1980's. The 'high tech' slotted pins in common use on US made guitars in that period had a shallow slot that would not clear the largest strings. So Martin continued slotting bridges until the late-1980's.
I remember when Martin historian Mike Longworth told me that they had changed to bridgepins with deeper slots, so that they no longer had to slot the bridges. I responded by saying, 'you went the wrong way'. He didn't understand, but by that time, I already had spent several years repairing bridgeplates and buying unslotted ebony pins from Europe.
Unslotted pins are superior, for several reasons:
1) unslotted pins are stronger and more durable
2) with unslotted pins, the string ball rests on a solid surface, and they can be rotated, so that the bearing surface changes each time they are inserted.
3) with slotted pins, the string ball rests aganst the same area every time, putting more stress on a weaker pin.
4) with slotted pins, the string ball presses against two knife edges, which are very delicate. Slotted pins (especially the cheap thermoplastic variety) will show wear in this area relatively quickly...often even before the owner realizes there is a problem. Unslotted pins can (and often do) last forever.
5) with slotted pins, the string at the ball is bent at a sharper angle, putting more force on the pin than it does with a slotted bridge. More force on a weaker pin means more damage to the pin, which will result in bridgeplate damage.
6) (very important distinction) Slotting the bridge allows the slots to be sized for each individual string. With slotted pins, the slots are large enough for the 6th string, which means a sloppy fit on the other five. Sloppy fit is asking for bridgeplate damage.

As a man with 40 years of experience in engineering, engineering management, and manufacturing having seen a large number of things go wrong and right in enormous volume (10s of millions), I disagree :~). For my money the slot belongs on the pin. I could be wrong.

One important rule of thumb for mechanical design: avoid sharp corners under stress where you can.

Your experience is not an unbiased statistically significant sample as the guitars that don't fail for some reason, or are not manufactured in volume, don't end up in your shop.

Only the big manufacturers have the numbers and feedback from failures and none failures to make a statistically significant determination.

The big manufacturers have made plenty of mistakes and needed to correct after some significant production, but they do correct. This is the very basics of quality control: measurement, statistical analysis, correction. Modern Industrial Engineering and statistical process control are clearly evident when you tour the Martin factory. The presumption that they are cheap or lacking intelligence, amplified with sarcasm, is not justified.

[murrmac123]

Originally Posted by jonfields45

I live near the Martin factory and with business connections here in the Lehigh Valley have had the opportunity to spend time with Dick Boak and Chris Martin. With the tooling they have to make guitars they don't need to compromise design to save money on unassisted hand work. While they understand designing to a price point and product tiering, they are not about doing anything wrong for pennies.

I find your faith incredibly touching.

Misguided, admittedly, but touching, nonetheless.

[mirwa]

Originally Posted by jonfields45

Only the big manufacturers have the numbers and feedback from failures and none failures to make a statistically significant determination.

I agree entirely with that statement. Many times we repairers/small builders come to conclusions which differ from industry, we come to those conclusions from what crosses out benches but tend to forget we only see a tiny part of the real picture.

Like others, I too have always wondered why the bridge holes are not tapered, it makes no sense to me and I could not envisage it being for a cost saving reason either.

Steve

[charles Tauber]

Originally Posted by jonfields45

As a man with 40 years of experience in engineering, engineering management, and manufacturing...

As a man with 40 years of experience in engineering, engineering management and manufacturing, please explain to me the engineering principle behind inserting tapered pins in non-tapered - or stepped - holes. How is doing so a better - or an even equal - practice to using tapered pins in tapered holes?

Engineers have been using tapered pins in tapered holes for quite some time: I'm unable to find any use of tapered pins in non-tapered holes in any application but for one company in one use. If this practice is not to save time, effort or money, then why is it being done? Does this same company use tapered end pin in non-tapered holes? If not, why not? If a tapered bridge pin in a non-tapered bridge pin hole good, then why wouldn't it also be good for end pins, putting tapered end pins in non-tapered holes?

One important rule of thumb for mechanical design: avoid sharp corners under stress where you can.

Where are the sharp corners in a slotted hole? Where is the practical evidence that slotting bridge pin holes causes detrimental stress concentrations? Is that evidence, by your argument, statistically significant?

Your experience is not an unbiased statistically significant sample as the guitars that don't fail for some reason, or are not manufactured in volume, don't end up in your shop.

To be clear, your argument is that the observed failures with un-slotted pin holes don't happen in sufficient numbers to "matter" but the decades of instruments made with slotted pin holes that don't have failures can be ignored?

The big manufacturers have made plenty of mistakes and needed to correct after some significant production, but they do correct.

Some do, some don't. Those that don't continue to produce the same goods, with the same escaping defects and design flaws as long as consumers are willing to buy those products. If consumers continue to buy those products, there is no compelling reason for the company to change their design or manufacturing practices. If consumers no longer buy those products, the company either stops manufacturing them, changes them to improve them, or goes out of business.

I can think of many examples of companies that produce products with high failure rates and poor designs that just keep manufacturing them year after year after year and never change or fix them. In many companies, Marketing/Sales drive design, not Engineering.

This is the very basics of quality control: measurement, statistical analysis, correction. Modern Industrial Engineering and statistical process control are clearly evident when you tour the Martin factory.

"Quality", as you are well aware, is an interesting thing to define and can be defined in different ways by different people - and has been over the decades before and after Deming. Statistical process control, as you are also well aware, is only of value if one is measuring, analyzing and correcting "the right things", those that are relevant.

"Quality", like statistical process control, is not a single, absolute thing. It is whatever and however those defining it chose to define it. For example, let's chose to define "quality", a "quality product", or an "in-control process" as ensuring that every one of the thousands of guitars leaving our factory has six bridge pins installed in the bridge. If we inspect the statistically relevant number of guitars - ensuring we have the right sample size to statistically ensure that we meet or exceed our acceptable level of escaping defects - and find that "enough" of them have all six bridge pins prior to being shipped from our factory, we have achieved what we set out to do - we have "quality" and an "in-control process".

However, we did not include in our definition of "quality" that every bridge pin must be fully seated/protrude from the bridge a uniform amount. We didn't include that all six must be of the same color. We didn't include that the slots must all face the strings. We could have, but did not. But, by our definition, we have a quality product that has an in-control manufacturing process.

So, when one of our retailers calls our factory and says, "Hey, nice guitar, but I've got one that has four white bridge pins and two black ones", the factory's response is, "Oh, that's okay, it's within spec, we only need to unsure that we have six pins and since it has that, it's good to go." The retailer reported the "escaping defect", but the factory said, it isn't a defect, as we, the factory, define a defect. Therefore, it is a quality product and was manufactured to our quality standard, SPC 'n' all.


Mark Twain is reported as having said the following:

There are three kinds of lies: lies, ****ed lies and statistics.

In your 40 years of professional life, you know only too well that for statistics to be of any relevance they must be applied intelligently, as the above ridiculous bridge pin example illustrates. You also know that not all companies do so, or do so uniformly. If not careful, particularly for large companies, "quality" can take on a life of its own entirely apart from the products or services that company produces or provides.

The presumption that they are cheap or lacking intelligence, amplified with sarcasm, is not justified.

You said it yourself, that "they understand designing to a price point and product tiering..." Colloquially, this known as saving money, being cost-conscious or, more derogatory, as being "cheap".

I've read no one stating that "they" are lacking intelligence. I've also not seen any sarcasm. Instead, I see people attempting to have a rational, objective discussion.

[jonfields45]

Originally Posted by mirwa

I agree entirely with that statement. Many times we repairers/small builders come to conclusions which differ from industry, we come to those conclusions from what crosses out benches but tend to forget we only see a tiny part of the real picture.

Like others, I too have always wondered why the bridge holes are not tapered, it makes no sense to me and I could not envisage it being for a cost saving reason either.

Steve

Here's a possibility...

You see some awesome looking bridge pins and decide to dress up your guitar with tapered bridge pin holes. Unknown to you they're slightly over sized, but the humidity is low and you push them in with some force. Then that summer you try to change your strings and can't get some of the pins out.

Sell a few million guitars and you might discover all sorts of failure modes.

[redir]

I Think there are plenty of real world examples out there of where engineers make the the designs and the bean counters get their way and alter them for the bottom line.

Like I said before, for the most part what Martin does is 'good enough.' And statistically a certain number of their guitars will have zero problems for all their lives especially if they are properly taken care of.

[Howard Klepper]

It can be amusing to see how often people start from the assumption that the overriding goal of a major manufacturer of a product must be to improve their product, and conclude that any changes they make have been scientifically determined to make the product better. Then they go on to state that the big manufacturers have so much greater knowledge and resources that criticism by people who actually have to deal with the results from those changes must be misinformed. [This is very dangerous reasoning. Writ small, it may lead to a bridgeplate failure. Writ large, it may lead to a self-disempowered citizenry who believe that they must trust whatever those who have access to greater information and resources tell them.]

The problem is that the fundamental assumption behind this reasoning is false. The overriding goal of major manufacturers is to make a greater profit in a competitive market. Anyone who thinks that this is mostly done by making a better product is in thrall to a painfully naive picture of how real markets and businesses work.

[John Arnold]

Your experience is not an unbiased statistically significant sample as the guitars that don't fail for some reason, or are not manufactured in volume, don't end up in your shop.

Guitars end up in my shop for a number of reasons, not just for worn bridgeplates. In any event, I do inspect all of them for the common issues. I also see many, many guitars that are not in my shop, since I do have many friends who play and collect. In many cases, these are six figure guitars.

I am not interested in statistically significant samples. I am interested in understanding why guitars fail, and how to repair them cleanly and efficiently. The last thing I want to do is deliver a repaired guitar to a customer without due diligence to prevent the same failure in the future.