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Stupid people tricks.


Ken_N

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The people would be ME!

The strange buzz on the A string on my Cello around D to D#? I was testing it today, and it is only there when you pluck it hard. Bow it, and it is fine.

I know what that is:

Fret buzz!

I thought I had the fingerboard set before I glued it on. 2mm relief on the bass side, a bit over 1mm on the treble side. I might have played with it some after gluing it on, and must not have paid attention to what I was doing. At least it should be an easy fix.

The projection went from 83 to 81. So now the strings are 7 - 9mm to the middle.

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33 minutes ago, Ken_N said:

…Fret buzz!…

I have encountered something akin to cello fret buzz.  I suggest that you test the area where the buzz is with a short straight edge — maybe 3 to 6 inches long — resting on the finger board parallel to the strings.  You are looking for a high spot that the straight edge will rock on.  When you find it, plane it off.

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Hah! I'm not getting through. The string height over the board was lower. Now it is up to 9mm on the C and 7mm on the A, to the middle of the string. To the middle seems like an odd way to measure.. So now the strings seem a bit high. It doesn't seem to be moving now. Maybe it has gone where it wants to be. The belly rose, or the nut rose.

The high point of the bump is right at the end of the neck. It is a bump right in the middle of the relief. It would be hard to carve in unless you thought about doing that.  Either the finger board, or the neck, or both, wasn't completely flat when I glued it. It is hard to believe that a stiff finger board would bend like that. There are no gaps on the glue line.

Now. Maybe I just didn't look at it good? 

Is a projection drop of 1.5mm or so normal?

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You have to remember that when you're gluing the fingerboard on, you are doing it with hot, wet, hide glue. On something like a cello or bass, things will also change with humidity and temperature changes. It sounds like you tried to finish the fingerboard before you glued it on. That's a problem for exactly the reasons that you're seeing. A fingerboard should always be checked for scoop when the final finishing is done after gluing. This is done before you put the nut on. It sounds like you'll need to remove the nut to re-plane the fingerboard. If the string clearance is too high, you'll have to trim the bridge down.

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Yes, the strings are a bit high.  You need to remove the bump in the finger board at the end of the neck that is causing the buzz.  You also should check the lengthwise relief ("scoop") of the fingerboard and correct it, if necessary.  After doing this, check the string height again.  If they are still too high, your options would be to lower the bridge or raise the fingerboard.  There are several ways to raise the finger board.

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You could get a straight grained board the length of the fingerboard and clamp it at the nut and place a spacer at the hump then clamp the free end of the fingerboard to it to pull the fingerboard   up about twice the height that it is now bent down. This is going to be to reset the fibers in the fingerboard. Keep it wet for a while, then dry it with a heat gun, probably several times, checking it in between. If it bent this easily once it will probably bend back just as easily. You'll have to watch for twisting and spontaneous combustion. (kidding)

I know that you used some strange wood. With any unknown wood source and type it is recommenced to wet and redry to check for long term stability, or this might happen.

I wet and dry my boards several times, and this warping that I too have experienced, has disappeared from my life.

If you get it to stay, then you'll need to  resurface the entire board.

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Looking at the cello this morning, I see that the bridge was tipped way forward. I don't know when that happened, I thought I was watching that. Moving it back to straight, it still has the original 83 mm projection, and the strings are 6 and 8 mm above the fingerboard; about where I had them, because I didn't know how it would settle.

So it hasn't moved at all. 

I still have the buzz on the A.

There is also a strange metallic buzz that comes in the decay sound if you pluck the C really hard. No other string will give it. It seems that if I hold the C fine tuner on the tailpiece it isn't there. But maybe I just don't pluck it as hard then. You get the same sort of sound if you bang the metal end pin shaft. 

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Thanks Mark. I usually make my own tailpieces, but ordering a Whittner tailpiece was fast and easy. Thanks for the tip on fine tuners David.

I'll pull the strings off, and plane down the offending bump. Actually, I'll probably use my plane blade scraper. It worked pretty good on it. Holding it almost parallel with the length will find the high spot easy.There is relief on either side of it.

It's cool how you can feel the sound everywhere.

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I worked on it for about an hour an a half yesterday. I used a 6" scale, and moved it from the end of the board, and then in 2 inches at a time, looking for, and finding high spots. It seems like I've taken a lot off the area by the end of the neck, but it still buzzes. Drawing the path of the strings with a pencil helps. I was using a scale that was too flexible, and that doesn't help at all. The drawn lines helped.

I bottomed out the C fine tuner. No buzz.

But.

The entire string now feels more flexible, and I have a slap bass! 

Really. The string slaps the board when I pluck hard, and it feels way more flexible. 

Maybe I'll have more time today.

I didn't even touch the bass side of the board.

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" I was using a scale that was too flexible," Were you using it flat on the board? You're supposed to use it on edge, and I don't think that I've seen a scale that is flexible in that direction.

"The entire string now feels more flexible" Is it in tune? The only way that a string can be more flexible is if it's looser.

Maybe if you tell us what the string clearance from the fingerboard is at several points, we might get more of a clue.

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Sighting down the fingerboard with light reflecting off it's surface is a very good way to see irregularities.

Do you still have "relief" on the A side after that work?  I typically use more than 1mm. The longitudinal concavity has to be very smooth along it's entire length, or at least in the lower pitched half of the A string to avoid buzzes.

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Ahh. I just found a cool way to check relief. The A is 5mm above the board. If I push the string down to the end of the fingerboard it has about 1.2mm clearance at the end of the neck. Probably not enough. The clearance at the nut is less than a thin card Maybe .02" Using the same trick, the C is 7mm above the board. At the end of the neck it has only slightly more than the A string has. The string has a little over a mm clearance at the nut, a credit card fits. I thought that I had 2mm!

The actual measurements there are 3 1/4 mm on the A string (and I can feel the scale rock!) and 4 1/4 mm on the C.

There just isn't enough clearance. I need to get a long solid straight edge. The longest solid one that I have is 12 inches. The 18" flex rule flexes. Then go through, and check for rock, like checking for high frets on a guitar.

The relief actually looks bigger and smoother on the side that I worked on. 

So far this is the hardest part about making a cello: next to putting the sound post in.

Making a cello is a piece of cake. Setting it up is hard. 

Thanks Doug for the suggestion to measure what I actually have. I should have thought to do that.

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"Ahh. I just found a cool way to check relief. The A is 5mm above the board. If I push the string down to the end of the fingerboard it has about 1.2mm clearance at the end of the neck."

Did you come up with that yourself? I don't know anyone who measures string clearance that way, and I doubt that it gives us any information to help you. Just keep your fingers off the string and measure the clearance from the bottom of the string to the fingerboard in several places.

Use the edge of the small scale, and look for high spots. This should be done with the strings and nut OFF, so that you can plane any offending high spots.

I'm thinking that maybe you should take a set-up course.

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A string is a straight edge, A number of shops I've worked in use then as such,,,at least as a first glance, to size up a situation. Hold the string down on both ends of the board and eyeball and maybe measure.

If the board is bent backwards, then shim both ends equally to raise it up enough to assess the situation.

If the large end of the board is bent down, hold the string down at the nut and check the length of the board that is parallel with the string and observe where the board drops.

I am having a difficult time understanding exactly what it is you are describing anyway.

March onward Ken the Fearless!

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I have the curve on the A and D looking good. Nice and smooth. Checking with different lengths of scales and broken carbide endmill shafts for "fret rock" I don't find any. But I only got the relief to about .03" The D does not buzz, but the A will, unless I push hard with my nail on the string. Bowing you don't even NEED to hit the board. But that's a whole different thing. 

Sliding the finger up and down the sting like a glissando, up the board, the A still isn't perfect from about C to D#. Plucking on the NUT side of the string you find the high spots where it needs to go down  Really, the high spots stand right out doing that. We will see today if that system pans out. The D string has no problems except way at the end of the board, and that is going backwards (the end of the board is a bit rounded over?). I'll smooth that up anyway.

I guess .03 clearance looks like a lot to me. I thought it was way over 1mm. Maybe I should get a set of feeler gauges. I had some, but I sold my machinist box with some things in it.

I checked the other 2 strings like that, and they have more problems. They don't buzz, but I'll fix them up. The C slipped after I retuned it when I bottomed out the tuner. That's why it felt loose. It was at A. Tuned up, there is still no buzz at less than a mm of clearance. The A appears to need more than the C! That is the difference between 7mm above the board, and 5mm above the board.

Are those numbers about right? If they need to go down, the relief needs to be deeper. I set up a violin really low,and it works just fine. 

I bought a 16 X 24" carpenters square at Menard's yesterday. A good find for less than $8. I can lay it up right against the string and I know that is where the string goes.

I'll pull out the little plane today and make the A curve deeper; especially in the middle area of the neck. Then smooth up the other side.

Evan; scraping with a plane blade across the board I noticed high points in regular spacing. It must have some curl. That doesn't usually help.

 

 

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