JLD Bridge Doctor

[DanSavage]

Originally Posted by Rodger Knox

Problem is, on the frets.com site, the neck is under string tension, and your measurement is not. Either method will work, but if there's no string tension, where the straightedge hits the bridge is different by the amount the top pulls up under string tension, and that needs to be taken into account.

How much difference are we talking about here? An inch? Half an inch? A quarter of an inch? One-eighth of an inch? A sixteenth of an inch? A thirty-second of an inch?

Just saying there will be a difference is not quantifiable. Have you measured the difference between how much the top rises when under tension vs. when it's not?

[DanSavage]

Originally Posted by Todd Yates

You only shave the bridge if the bridge started out excessively tall. In that case there can be both tonal benefits and cost savings. It needs to be done correctly though, not as shown in that photo.

Bridge or saddle? IMO, shaving the bridge is an extreme measure that's done in lieu of the proper remedy, which is a neck reset. Again, IMO, even shaving a saddle is a crutch. Some saddles, such as the Ovation OPC1 can't be shaved. So, once the action gets too high, the only remedy is a neck reset.

Originally Posted by Todd Yates

I don't think we're that far apart then. I misinterpreted your original statement.

Frank uses a 24" straightedge though. An 18" straightedge can lead to significant errors. Regardless, I can (roughly) assess the need for a neck reset by looking at the action, saddle, and bridge heights. I can even measure (again roughly) with 6" pocket ruler, which is more suitable for carrying into a guitar shop than a 24" straightedge.

Fair enough. Significant? Quantify the word, 'significant.' An inch? Half and inch? A quarter of an inch? An eighth of an inch? A sixteenth of an inch? A thirty-second of an inch?

I agree. I can look at the height of the saddle above the bridge and the height of the strings above the 12th fret and see immediately whether the neck angle (top belly/collapse) is affecting the action.

[mirwa]

Originally Posted by DanSavage

BSome saddles, such as the Ovation OPC1 can't be shaved. So, once the action gets too high, the only remedy is a neck reset.

Unfortunatley its pretty well impossible for most and extremely difficult to a few to do a neck reset on an ovation.

So most will resort to anything that is possible to keep the guitar going, nothing wrong with that, we all have different approaches

Steve

Originally Posted by DanSavage

Bridge or saddle? IMO, shaving the bridge is an extreme measure that's done in lieu of the proper remedy, which is a neck reset. Again, IMO, even shaving a saddle is a crutch. Some saddles, such as the Ovation OPC1 can't be shaved. So, once the action gets too high, the only remedy is a neck reset.

Shaving the bridge should not be undertaken without good reasons, but sometimes there are good reasons. Martin for example uses at least three different bridge heights for the sake manufacturing speed. Once they initially set the neck, they choose the bridge height that fits. A standard Martin bridge is about 0.340" tall, but the tallest typically found on Standard Series and higher guitars is 0.375". If you have the tallest bridge on your guitar, you can lower that to 0.0340" without issue. In fact, it will likely improve the guitar by reducing the weight of the bridge.

Why would you consider lowering the saddle a crutch? Adjusting saddle height within reasonable limits is standard practice for adjusting action.

Originally Posted by DanSavage

Fair enough. Significant? Quantify the word, 'significant.' An inch? Half and inch? A quarter of an inch? An eighth of an inch? A sixteenth of an inch? A thirty-second of an inch?

I've never tried to quantify it, but I know the difference is enough to make an 18" straightedge unreliable for that use.

[DanSavage]

Originally Posted by mirwa

Unfortunatley its pretty well impossible for most and extremely difficult to a few to do a neck reset on an ovation.

So most will resort to anything that is possible to keep the guitar going, nothing wrong with that, we all have different approaches

Steve

All US Ovations since 1984 have Kaman bar neck, which is to say, a bolt-on neck. Doing a reset on these is should be no different than doing a reset on a Taylor.

The foreign-made Ovations have always had glue-on necks, but with the right technique to soften the epoxy, these can be converted to a bolt-on neck. Here's a thread on the OFC where a member did just that. (See: Celebrity Deluxe CC247 Neck Reset)

[DanSavage]

Originally Posted by Todd Yates

Shaving the bridge should not be undertaken without good reasons, but sometimes there are good reasons. Martin for example uses at least three different bridge heights for the sake manufacturing speed. Once they initially set the neck, they choose the bridge height that fits. A standard Martin bridge is about 0.340" tall, but the tallest typically found on Standard Series and higher guitars is 0.375". If you have the tallest bridge on your guitar, you can lower that to 0.0340" without issue. In fact, it will likely improve the guitar by reducing the weight of the bridge.

Why would you consider lowering the saddle a crutch? Adjusting saddle height within reasonable limits is standard practice for adjusting action.

I've never tried to quantify it, but I know the difference is enough to make an 18" straightedge unreliable for that use.

I didn't know that about Martin bridges, but that's an interesting fact. How do they determine which bridge is the right height? A straight edge on the fretboard?

I should have been more clear. Lowering the saddle within reasonable limits to adjust action is fine. But, when you lower the saddle excessively in lieu of a neck reset, it's a crutch.

I haven't had that experience. The neck is straight except for a slight amount of relief, right? Proper relief is .010" to .020". So, for the sake of discussion, let's split the difference at .015". (1/64")

From the mid-point of the neck with that kind of relief, the straight edge will only be .030" or a 1/32" higher at the bridge than if we'd measured from the 1st fret. I know that's correct because I just did a simple CAD drawing of a neck with a 25.5" scale and measured it.

1/32" of an inch is not a significant amount when it comes to determining whether the neck needs a reset. So, it doesn't really matter whether you're measuring from the 5th or 6th fret or from the 1st fret when you're checking the neck angle.

[Rodger Knox]

Originally Posted by DanSavage

How much difference are we talking about here? An inch? Half an inch? A quarter of an inch? One-eighth of an inch? A sixteenth of an inch? A thirty-second of an inch?

Just saying there will be a difference is not quantifiable. Have you measured the difference between how much the top rises when under tension vs. when it's not?

Yes, I have measured that on several guitars. Sometimes it's significant (1/32" or more), sometimes not. How can you use where a straightedge hits the bridge without string tension if you don't have a pretty good idea what string tension will do?

Originally Posted by DanSavage

I haven't had that experience. The neck is straight except for a slight amount of relief, right? Proper relief is .010" to .020". So, for the sake of discussion, let's split the difference at .015". (1/64")

From the mid-point of the neck with that kind of relief, the straight edge will only be .030" or a 1/32" higher at the bridge than if we'd measured from the 1st fret. I know that's correct because I just did a simple CAD drawing of a neck with a 25.5" scale and measured it.

1/32" of an inch is not a significant amount when it comes to determining whether the neck needs a reset. So, it doesn't really matter whether you're measuring from the 5th or 6th fret or from the 1st fret when you're checking the neck angle.

A slight amount of relief is 0.002", a large amount is 0.007". Where did you get your numbers?

Typical specs are 3/8" bridge thickness, 1/8" saddle above bridge, 1/2" height above top. You can lower the action by lowering the saddle about 1/16" before a reset is in order, that drops the height of the strings above the top to 7/16".
And you are saying 1/32" isn't significant in determining the need for a reset?

[redir]

On the guitars I build I expect the change due to top rise and neck relief to be about 1-2/64 under tension. That's a good place to start and as such I make sure the straight edge test takes that in to account. Obviously an over built guitar will hardly budge but aiming for a straight edge, strings off, to be about 1/32 over the saddle is about right in any case I think.

It's a general rule of thumb that has worked well for me fwiw.

[murrmac123]

FWIW, Grit Laskin told me that he builds his guitars so the top rises 1/16" under tension.

[mirwa]

Originally Posted by DanSavage

All US Ovations since 1984 have Kaman bar neck, which is to say, a bolt-on neck. Doing a reset on these is should be no different than doing a reset on a Taylor.

Actually not quite.

A kaman bar is nothing more than an aluminium insert/casting, it does not mean the neck is bolt on.

The issue with doing neck resets on ovations is 90 plus percent of them are epoxied on, not the easiest of glues to get apart, hence my earlier comment, pretty well impossible for most and extremeley difficult for some

Steve

[DanSavage]

Originally Posted by Rodger Knox

A slight amount of relief is 0.002", a large amount is 0.007". Where did you get your numbers?

I found it online. But, no matter.

Let's do the math using your numbers. 1/64" is .0156". 1/128" is .0078", 1/256" is .0039", 1/512" is .00195". FWIW, 20# printer paper is .0035" thick.

So, with a neck relief of .002", (1/512") the rise of the straight edge at the bridge when measured from the 6th fret will be .004", or just over 1/256".

I don't have a ruler that measures in increments of less than 1/64", but are you saying that .004", or the thickness of a sheet of paper will introduce such a large error that it negates measuring from the middle of the neck?

Out of curiosity, how do you measure 1/256" with a ruler?

Even with a neck relief of .007" which you say is a large amount, the rise of the ruler at the bridge will be .014, or just under 1/64".

With a neck relief of .004", which is about halfway between what you say is a slight and large amount, the rise of the straight edge will still be only .008", or just over 1/128".

I guess if you're shooting for 100% absolute precision, this would demand measuring from the 1st fret. But, I can live with an error of 1/256" to 1/512".

[DanSavage]

Originally Posted by mirwa

Actually not quite.

A kaman bar is nothing more than an aluminium insert/casting, it does not mean the neck is bolt on.

The issue with doing neck resets on ovations is 90 plus percent of them are epoxied on, not the easiest of glues to get apart, hence my earlier comment, pretty well impossible for most and extremeley difficult for some

Steve

The glass transition temperature (Tg) of epoxy determines at what temperature it will soften and become pliable. Some epoxies are high-temperature, up to 350° F. Most are somewhere around 160° F.

As my link to Ken's Celebrity neck reset shows, the Tg of the glue used for Ovation necks is lower than the temperature of boiling point of water. The trick is knowing how to apply the heat in such a way that it will soften the epoxy. Ken's thread shows a really good way to do so.

Here's the 1977 Patent drawings for the Kaman Bar. (See: Ovation "Kaman Bar" Patent (1977))

Here's the parts of the description that describes how the neck attaches to the body. Between the drawings and description, this sounds like a bolt-on neck, to me.

[DanSavage]

Originally Posted by murrmac123

FWIW, Grit Laskin told me that he builds his guitars so the top rises 1/16" under tension.

That pretty much agrees with what I've seen. I try to make sure the straight edge is about 1/16" above the top of the bridge and once I put the strings on it, the straight edge is just kissing the bridge.

[LouieAtienza]

And you are saying 1/32" isn't significant in determining the need for a reset?

I would think, if faced with this, giving a client options, I'd tell him to rather shave down the saddle or make a new one, and save the neck reset for later.

But yes, in agreement with Dan, using a straightedge on a neck with about .004" of relief gives you a whopping angle error of something like .06 degrees. But then why the need as some point out for such a long straightedge? From the 8th fret or so to the fretboard end should be relatively straight anyway, barring any structural problems. Why take into account where the relief is, since we know, unless it was built into the fretboard to begin with, that the relief is induced by the string tension and adjusted by the trussrod?

But really, are we so lazy that we can't straighten out the neck before checking neck pitch (which is usually the way we do it when checking the neck angle in the first place when attaching the neck)? Can obviously be done with string tension, and eliminates any error, however microscopic. Even just sighting down from the headstock area, looking from the 8th fret out to the bridge, one can quickly determine if the neck is a candidate for a reset.

Likewise, can mere mortals tell the difference in sound between a guitar whose string height is 7/32" and 1/2"? And attribute that change to just the string height?

Out of curiosity, how do you measure 1/256" with a ruler?

Feeler gages...

[mirwa]

Originally Posted by DanSavage

Here's the parts of the description that describes how the neck attaches to the body. Between the drawings and description, this sounds like a bolt-on neck, to me.

Thats the joys of information gleaned from internet searches, when in reality if you actually had done the job which clearly is evident you have never done, you would know that they are not all equipped with bolts and most of the ones I have ever seen easily a hundred or so are epoxied in place.\


Thats also a new one on me, epoxy that releases its strength at a temperature less than boiling point of water, wow, never seen that yet, epoxy is a chemically hardened product, it not a product that sets from evaporation or exposure to air.

I get my information from doing the job.

Steve