Sanding the ends of the soundpost


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In a different thread, a lot of folks said they use a knife to cut the ends of the sound post---to fit the ends to the sound plates.

 

I've been thinking that sanding the ends would be easier and would give an accurate result.

 

What would be wrong, if anything, with sanding the ends of a sound post?

 

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Michael Darnton makes the point that with a knife, you can see how much you're taking off. If you sand or file, you can't. I use a file to make sure the cut is flat... Sometimes the knife leaves a crown or dome.

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do you mind if I use a chisel? :)

That's what I use too, a wide one. With the long straight surface as a reference, I find it so much easier to judge the angle and depth of the cut, before any cutting is done. It's one of many things I've learned from people who I was supposed to be teaching. :lol:

 

That's one of the great things about taking on apprentices, as long as the "teacher" isn't stubborn enough to think they know everything already.

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do you mind if I use a chisel? :)

Lol. Knife, chisel...that doesn't matter. Files, sandpaper on a stick or otherwise, RASPS...gross.

I live in an area where people do all kinds of stuff, or nothing at all, at every step. Yet we all charge basically the same.

Of course there is someone way, way better than me too. But the gamut of what is accepted is nuts.

OP, please don't take this the wrong way. Cutting corners with sandpaper is stupid.

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I'm an internet-trained shade tree fiddle mechanic. I did my first soundpost fittings by sanding the ends. After I learned that nearly every skilled luthier did it with a blade and most considered it impossible to do an adequate job with sandpaper, I started trimming the ends with a blade. After a dozen or so attempts I got to where I could do as good a job with a blade as I could with sandpaper, and it's the method I continue to practice.

But I still don't understand why the use of sandpaper is frowned upon so universally. I'm not talking about ripping off a chunk of 60 grit and going to town. I mean placing a piece of fine sandpaper on a perfectly flat surface and very carefully rubbing the end of the post against it while maintaining a constant angle. I realize that it's humanly impossible to do this without introducing some convexity to the end of the post, but it seems like the convexity is very slight, and a perfectly fitted soundpost will be slighly convex on the end (I know, it's very, very slight).

Why is the same motion used to hone a knife or scraper to a precise bevel unsuitable for a soundpost?

Like I said, you guys are way smarter than I am about these things and I need to take advantage of every chance I can to improve my blade skills, so I'll continue to use a knife or chisel. But I still wonder.

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Chisel... I like it!   :)

 

I was cutting a post yesterday, and wishing for a miniature miter cutter... one of the ones that works like a paper cutter.

 

shave-your-miters.jpg

Addie, My jig is something like that miter trimmer. I took several photos. The great thing about the thing is it cuts perfectly flat sharp edged posts. No humps or hollows. I can take tiny thin shavings off perfectly flat every time. I chucked it in the vice cause I needed a free hand. I always just hold it in my hand. I pulled the post up so you can see how nice the cut is. I figured the angle and cut one end just a bit shallower. Occasionally I have to adjust the angle of the cut but not very often. It wasn't as easy to make as I thought it would, as I remember. Everything has to be kept straight and in line.
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I guess anything is stupid to someone who hasn't learned how to do it correctly. Thanks bunches for the compliment.

I was responding to OP who knows the correct way but apparently considers it too much effort. For someone serious who had not learned correct setup yet, it is not a consideration to do it the other way in future.

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Addie, My jig is something like that miter trimmer. I took several photos. The great thing about the thing is it cuts perfectly flat sharp edged posts. No humps or hollows. I can take tiny thin shavings off perfectly flat every time. I chucked it in the vice cause I needed a free hand. I always just hold it in my hand. I pulled the post up so you can see how nice the cut is. I figured the angle and cut one end just a bit shallower. Occasionally I have to adjust the angle of the cut but not very often. It wasn't as easy to make as I thought it would, as I remember. Everything has to be kept straight and in line.

 

Berl, you're the man!

 

This is an interesting tool, and very cool.

I'm curious, do you get one end carved correctly first, and then have to take it in and out a few times, in order to get the length absolutely perfect?

 

I'm considering making my own version...

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Berl, you're the man!

 

This is an interesting tool, and very cool.

I'm curious, do you get one end carved correctly first, and then have to take it in and out a few times, in order to get the length absolutely perfect?

 

I'm considering making my own version...

Craig, I cut both the same angle and then try. Another good thing about this is you can micro fit the post. You can take very thin shavings. Just leave a very small amount of the post sticking up, lay your chisel flat on the jig and shave it off. If you've carved your plates well and they have a smooth flat surface, your post will fit like a glove.
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Well, I'm going to say that while I cut and fit the post with a knife, I often take one very light swipe holding the cut end flat on my sanding board with 400 paper (when I'm finished fitting).  I also often use a little bit of chalk on the end.  I find the post is easier to move small amounts (fine adjustments) that way.

 

So there.   :)

 

I believe the well known maker(s) who use a jig on a fine disk sander mentioned are Mr. Curtin & Mr. Alf.

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Berl, that as awesome! One question though, will that work for any violin, or just specific arches? What if the top or bottom of the post for a particular fiddle needs a different angle to fit the arch?

 

Awesome indeed.

 

I will not answer for berl -

But I will guess here.

 I will say, that when I look at the photos he is providing, I can easily envision the slant on the wood being an angle that is a close approximation of a usual belly or a back arch, and then the post is simply held in position and cut to exactly fit whichever violin you're making the current post for...

 

So, it seems to me that this tool can and will hold the post firmer than your hand might?

In particular, as my hands get older... (not that I'm getting on in years mind you!)

???

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Hey, who am I to say...I am not the one showered with genius awards and medals. And chalk, I can see how that makes sense. For me, it's a knife...it's how I was taught, and it gets done fast and right. No one is telling me what to do. So if someone likes to use a silver spoon to cut it down, fine, as long as it's right. Whatever way anyone gets a perfect result, awesome. I prefer my way.

I think if someone concedes that one way is better but does something else because it's easier, it's a kind of cop out.

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I feel that what is making this subject slightly controversial is that sanding is the "music shop" approach to everything and requires no tool use or sharpening skills.  One could have a similar discussion over bridge feet (most luthier tool suppliers stock a little rolling jig for sanding these).  I believe that one should master the cutting techniques for parts fitting, but then use whatever gives you the best result in your own case (as well as refrain from going to war with those who open their breakfast egg at the other end.  :lol:).

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I never said that a knife was better. I'm trying to determine what's better for me. No solution fits everyone best.

That is perfectly true. For me, if I am going to spend 100+ hours on something, shaving off five minutes with sandpaper is not optimal.

You may find that it is justified. ..particularly because learning to do it with a knife is not quick or easy. If you perceive that there is a choice, there definitely is one! Do what is best for you ... I am a good liberal (in the sense of accepting the moral pluralism in all things) and I hope you are not offended. I took your op as suggesting that you want to use sandpaper only because it is easier...like you were making the choice before hearing reasons not to.

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One of my former apprentices came up with a novel way to cut posts. It works on new violins, but not so much on old or oddly pinched arches.

 

A piece of apple ply, holes drilled at 90, 89, 88, 87...84 degrees. Important to use a good, square drill press table and have the correct orientation. 

 

Saw up the center, for relief, and install a cam clamp at the end. 

 

Slide post stock in. Cut end with flat chisel, loosen, remove, do other end-paying attention to keep the length close, and then check for fit.

 

I have found that it works best on flatter arches, and find that 87 degrees on each end fits many Chinese instruments to a T. 

 

Warning: If you use this too much, or use it in place of learning to properly cut a post, you are sunk.

 

I was recently told that the Alberti hand sander was orig. designed with sound post fitting in mind, but I wouldn't use if for that...

 

Further...I was told that files round things. I recall Mike Scoggins telling me that Carrie was wrong for using a file on the end of the post to flatten it. Lo and Behold, spending time with a bow maker friend, he uses files to flatten things. All things. 

 

I don't like sandpaper for a post, but if you can make it work, that is fine. If you have started using sandpaper because you don't want to put in the time to learn it with a knife and think that the abrasive paper is an acceptable alternative, I have no time for you.

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