The Amazing Shrinking Peg


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Things you learn when you're just starting out: Sanding down the shaft of a violin peg by even a small amount will have a huge effect on how far it goes into the pegbox. For a peg with a standard 1:30 taper, taking as little as 17 microns (0.017 mm) off the surface of the peg shaft all the way around will cause the peg to shift in the peg box by 1 mm. For scale, this means sanding down the surface of the peg shaft by the thickness of a piece of printer paper (about 100 microns) will cause the peg to shift by 6 mm, which is huge.

So this is how the head of peg I was "lightly" sanding to make it smoother and give it back its color ended up 3mm closer to the wall than before I started and the string hole ended up in the wrong place. It's all so clear now that I've done the math, but I wasn't expecting a bit of sanding would have that much of an effect.

Anyway, live and learn.

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The next factor you will need to add to the equation is humidity. Even if everything were perfect, things could drastically change with a drop in ambient humidity (or increase). Another thing to take into serious consideration when fitting pegs.

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6 minutes ago, Strad O Various Jr. said:

I find the application of peg dope makes raw pegs go in even further, and I have to compensate for that when fitting

Now that you mention it I remember having experienced that also with commercial peg dopes that contain

more lubricants like wax or soap, but in making my own peg dope I added more friction inducing solids like

chalk or pumice which made it of a thicker consistency that could build up to a layer.

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29 minutes ago, donbarzino said:

Now that you mention it I remember having experienced that also with commercial peg dopes that contain

more lubricants like wax or soap, but in making my own peg dope I added more friction inducing solids like

chalk or pumice which made it of a thicker consistency that could build up to a layer.

I don't use commercial pegdope, just soap and chalk.

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11 hours ago, Davide Sora said:

The next factor you will need to add to the equation is humidity. Even if everything were perfect, things could drastically change with a drop in ambient humidity (or increase). Another thing to take into serious consideration when fitting pegs.

Good point, Davide. Do you alter your peg fitting process depending on humidity on the day?

 

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7 hours ago, Bodacious Cowboy said:

Good point, Davide. Do you alter your peg fitting process depending on humidity on the day?

 

Yes, I look at how the humidity was in the period immediately before having to do the pegs (not a momentary change in humidity, but at least two or three days) and adjust accordingly by staying more close or far from the pegbox. It's not an exact science, but useful to try to avoid blunders.

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52 minutes ago, Davide Sora said:

Yes, I look at how the humidity was in the period immediately before having to do the pegs (not a momentary change in humidity, but at least two or three days) and adjust accordingly by staying more close or far from the pegbox. It's not an exact science, but useful to try to avoid blunders.

Thanks. Something to bear in mind. I've never had pegs move in/out too much with humidity changes, but even a little bit can be irritating when you've taken the trouble to fit them to a nice length.

 

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Would you think 4f fine pumice stone would work as well as chalk dust or would that be too abrasive?

Also... do you suggest blackboard chalk dust or climbers' / gymnastics chalk? or is there a difference?

Thx... Mat

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I tried pumice once, it don't remember it working, the problem with powdered chalk is its hard to remove from the peg and discolors it, I have yet to find a kind of chalk stick that works at all, the formulas have changed, and my guess is they're half plasticizers. I'm using the powdered chalk they sell in bottles at the hardware store for marking lines etc. It does work very well, pegs trun smoothly with no clicking but quite a bit of friction, however there are traces of the chalk visible on the pegs, I use the reddish color, I don't think they make black.

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2 hours ago, Strad O Various Jr. said:

I tried pumice once, it don't remember it working, the problem with powdered chalk is its hard to remove from the peg and discolors it, I have yet to find a kind of chalk stick that works at all, the formulas have changed, and my guess is they're half plasticizers. I'm using the powdered chalk they sell in bottles at the hardware store for marking lines etc. It does work very well, pegs trun smoothly with no clicking but quite a bit of friction, however there are traces of the chalk visible on the pegs, I use the reddish color, I don't think they make black.

Real chalk, which is what you find in the White Cliffs of Dover, is a very specific form of limestone composed of minute fossils called "coccoliths", and, ideally,  is what you want for peg dope. 

Most of what is currently marketed as "chalk" isn't, a lot of it not even being calcium carbonate any more, calcium sulfate (gypsum) often being a major constituent of blackboard chalk.  Climbing chalk is usually magnesium carbonate, sewing chalk is actually talc, chalk-line chalk contains various things including titanium dioxide, and so on.  Whiting is sometimes the right material, but also may contain ground marble, oyster shells, and other such shiny stuff.

IMHO, the best way to get real chalk, if you lack a nearby deposit, is buying geology classroom samples.  :)

ttps://www.eiscolabs.com/products/esng0032pk12

https://www.amazon.com/Limestone-Chalk-Sedimentary-Rock-Specimen/dp/B083TC9Q6L

 

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12 minutes ago, Violadamore said:

Real chalk, which is what you find in the White Cliffs of Dover, is a very specific form of limestone composed of minute fossils called "coccoliths", and, ideally,  is what you want for peg dope.

So..., why is that what I want for peg dope, as opposed to the other possibilities?

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Just now, Mark Norfleet said:

So..., why is that what I want for peg dope, as opposed to the other possibilities?

How the little plates hang on the wood and each other, without being very abrasive.  It's a nanotech thing.  It's also what was used originally, back when "chalk" meant chalk.

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1 hour ago, Violadamore said:

Real chalk, which is what you find in the White Cliffs of Dover, is a very specific form of limestone composed of minute fossils called "coccoliths", and, ideally,  is what you want for peg dope...

Off topic:  I found your explanation of the compositions of different types of "chalk" interesting.  What I really want to know is what type of "chalk" would I want, ideally, for fitting bass bars and sound post patches?

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43 minutes ago, Brad Dorsey said:

Off topic:  I found your explanation of the compositions of different types of "chalk" interesting.  What I really want to know is what type of "chalk" would I want, ideally, for fitting bass bars and sound post patches?

I'm probably the wrong person to ask for that.  While I know that, microscopically, coccoliths look like little fancy hubcaps, while powdered crystalline material looks like road gravel, I don't "chalk" fit with chalk.  I use carbon flimsies pulled from old shipping documents, or dressmaker's carbons, depending on what works best in a given case.  :ph34r:   :D

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6 hours ago, Brad Dorsey said:

Off topic:  I found your explanation of the compositions of different types of "chalk" interesting.  What I really want to know is what type of "chalk" would I want, ideally, for fitting bass bars and sound post patches?

I found some art chalk sticks, sold as a pack of one white and one black, which were very expensive  but have none of the grittiness of blackboard chalk. I have found it to be perfect for fitting bass bars.

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31 minutes ago, Strad O Various Jr. said:

Black powdered chalk, same brand I was using, I'm going to order some

https://www.amazon.com/Tools-STRAIT-LINE-2032160-Permanent-Marking/dp/B0002UKSPU

So I checked the safety data sheet, and the Irwin chalk is mostly iron oxide and talc with a touch of crystalline silica... but hey, if it works well...

https://www.irwin.com/uploads/documents/59_IRWIN_Chalk_SDS_-_Midnight_Black_PerSt.pdf

an after thought... why not make up limestone chalk and color it black with shoe dye?... assuming limestone chalk would work better?

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