Sanding the ends of the soundpost


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Lo and Behold, spending time with a bow maker friend, he uses files to flatten things. All things.

Indeed bowmakers use files, but mostly files that are not flat. The files of choice are Grobet hand files which are very slightly arched in the first third, ending with parallel sides. This allows you to cut a slight hollow with the first part of the file, while finishing the file stroke to flat. This is much different than trying to make something flat using sandpaper on a flat board.

I do not consider sandpaper as an acceptable alternative for fitting posts, and we also make each post from raw wood not soundpost stock. A very influential open minded teacher told me once, after he kicked my ass making a nut with a plane faster than I could spin one down on the new workshop sander, "Develop a good relationship with your plane". I would expand that to say "Develop a good relationship with your tools". Wax on wax off.

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Indeed bowmakers use files, but mostly files that are not flat. The files of choice are Grobet hand files which are very slightly arched in the first third, ending with parallel sides. This allows you to cut a slight hollow with the first part of the file, while finishing the file stroke to flat. This is much different than trying to make something flat using sandpaper on a flat board.

 

 

I didn't know that about the files. Thank you. My friend is Robert Morrow, and he kicks my A** with a file. He would hand me something with a number written on it. That number was the number of file strokes I should be able to flatten it in. Fail...

 

I do fit the post, completely, with edged tools, be it chisel of knife, and I do fit bridge feet with a knife. You aren't "stupid" if you can't, but if you don't keep trying to fit posts with an edged tool, or bridge feet with a knife, you'll never be able to. It takes years...and as you progress, your idea of what "fits" changes, too. 

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I do fit the post, completely, with edged tools, be it chisel of knife, and I do fit bridge feet with a knife. You aren't "stupid" if you can't, but if you don't keep trying to fit posts with an edged tool, or bridge feet with a knife, you'll never be able to. It takes years...and as you progress, your idea of what "fits" changes, too.

Agreed, if you want to get good with your knife or chisel, use you knife or chisel. If you want to get good with sandpaper.....

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I know of a violin maker out west who uses a small, very precise disc sander with an angle jig for fitting posts.  He's got a good reputation and does quality work.  From people who I trust, they say his soundpost fit well.  'Edit: Now that I think about it, I think he does fine tweaking with a cutting tool though.'

 

I personally use a chisel.  I like this method because I have a lot of control, but I never really developed anything else to the same level (guess I don't really need to at this point).  I would imagine it hard to not round things over with sandpaper, unless I was using a jig like the guy I mentioned.  

 

When I started out in making I had a glass flat plate with sandpaper on it.  I used to always use that to flatten all kinds of things because I didn't feel as comfortable using a plane.  Once I got proficient with a plane, I realized I was rounding the heck out of things with the sandpaper.  

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I'm thinking that the biggest errors of soundpost fit have their origins in limitations of measuring, not in limitations of cutting or sanding.

I'm assuming you are talking about limitations in how well something actually fits as opposed to how well someone thinks it fits?

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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...

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.

Good on you for taking it upon yourself to learn. MN is a beautiful thing. So are knife skills.

I think you intuitively know the answer to your question. ..and for once I am not being snarky, just stating a fact.

Endgrain of spruce =/= steel blade. Spruce is all sloppy and soft and it needs to be cut cleanly. I am sure you can imagine why.

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I know of a violin maker out west who uses a small, very precise disc sander with an angle jig for fitting posts.  He's got a good reputation and does quality work.  From people who I trust, they say his soundpost fit well.  

 

I'll say that the fit is the end product. (get it... end product...ahh, never mind!) And the fit, if proper, can be acceptable, no matter how it is achieved.

 

That different posters think that they have achieved a certain method that places them in a far superior category - well, it's the fit you get rather than the method you use. So talk away.

 

The end of a soundpost - hand made, or store bought (neither does that make much difference, really, if the post is "right" in it's composition and dimension) only needs to be the correct length, and have the very small ends fit the inside contours well. The better the fit, the better post. No matter how it was shaped

 

One more time;

"as long as it fits well - what does it matter?"

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Ah, the greatest move ever made that can not be remade!

 

Hey y'all-Where do you keep the sand paper at?

 

Is it twoo, is it reawwy, reawwy twooo what they say about sandpaper?

 

And my favorite: We'll take the chisels and the knives, but NO SANDPAPER!

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Hans Johannsson, 2007-03-25

 

 

pic49.jpg

Now that's an impressive display of what i believe Roger would consider overengineering the process :lol:

 

Beautifully designed, though :)  One wonders if replacing the sander with a cutter head would make it more acceptable to knife purists?

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Yes, it's very neat but what's even more amazing is that "sanding the ends" it's on it's third page since yesterday. 

I believe I read somewhere here that Curtin and Alf use a similar system ? Maybe somebody could confirm ?

It looks to me far superior to other methods and has the advantage of being reproducible should one need a longer

( or shorter ) sound post.

 

The motor blows air the wrong way I should think.

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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.

Mr. Burgess:

Wow....what a refreshing attitude, especially coming from someone of your experience! 

 

And at the risk of groveling, many thanks to you, Jeffrey, Roger, Jacob, Matt, Jerry and other "big names" who continue to participate and contribute here.  What a great time it is that we live in, where information is shared much more freely than ever before.

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Mr. Burgess:

Wow....what a refreshing attitude, especially coming from someone of your experience!

And at the risk of groveling, many thanks to you, Jeffrey, Roger, Jacob, Matt, Jerry and other "big names" who continue to participate and contribute here. What a great time it is that we live in, where information is shared much more freely than ever before.

I feel the same way.
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Use a d**n knife.

For so many reasons.

 

You have made your disdain for alternativemethods perfectly clear in your several posts in this thread.

 

What I fail to see are the many reasons, other than the aesthetic one of doing it the traditional way.

 

Like CT asked many times, if it fits, why does it matter?  If it really does matter, please tell us why.

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"as long as it fits well - what does it matter?"

to me it matters, because I know that any first class violin maker can do it with a knife or chisel. So because I aspire to be a first class maker I feel that I should be able to do it with a knife or chisel too. Even if subsequently I may someday choose to do it differently..... :)

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to me it matters, because I know that any first class violin maker can do it with a knife or chisel. So because I aspire to be a first class maker I feel that I should be able to do it with a knife or chisel too. Even if subsequently I may someday choose to do it differently..... :)

That's an interesting perspective. Maybe setup techniques can be valuable training for making?

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Larry, you touched on a couple of common problems in fitting posts...

 

The first is the tendency for the edge of the post to split off when cutting the (unsupported) end grain with a knife (or chisel).  Hans J. Nebel taught us to use a single bevel knife, then moisten the end of the post with your tongue to make slicing the end grain easier.  Assuming you are holding the knife in the right hand, he would hold the post vertically in his left hand, wrapping his left index finger around the top of the post barely below the end to be cut.  He said to use the index finger as an "elevator" (or height guide), and place the bottom surface of the knife flat against that finger for control, and then slice across the post back towards your thumb in a single controlled slicing cut (see photo).  With enough practice, this is obviously a fine method for getting a flat surface on the post end, and I suspect is among the most commonly used methods. But as others have said, you can use whatever method gets you to flat surfaces and the proper fit.

 

post-33489-0-67543300-1396641502_thumb.jpg

 

My main problem with this method has been that sometimes the edge of the post wants to split away when you reach the end of the cut (towards the thumb). Often it's not a big split, but just a little ragged edge on the downstream side.  Of course, I can slice in towards the center of the post from each side, and avoid splitting, but that seems to defeat the goal of getting the flattest surface by making a SINGLE cut with the knife.  Berl's clever little jig would seem to avoid any splitting by supporting the post edge all round.  Haven't tried that yet.  I suppose that some may argue that if your knife is sharp, and you are taking a thin enough slice, there should be little tendency for splitting of the post edge.  And holding the post with  grain perpendicular to the knife surely helps.  But any other suggestions to avoid splitting? 

 

The other thing you mention is that slightly beveling the post edge (after final fitting) avoids the sharp edges that could dig into the soft spruce top when moving the post into position (or adjusting it later).  I worry about that, too, Larry, and we've all seen tops damaged that way by posts that were (or became) too long.

 

But the most experienced luthiers seem to strive for very sharp, clean edges on the post ends, and do not bevel or ease the edge at all.  While I understand the need for flat surfaces on the ends of the post for proper fit, isn't it sort of asking for trouble later to leave a very sharp edge (arris) on end of the post? For his new violins, Joseph Curtin had described his innovative method for inserting a (harder) maple veneer on the inside of the spruce in that area to avoid future dents from the post.  Interesting idea for new instruments.  But for existing ones, doesn't it make sense to very slightly bevel the ends of the (well fitted) post, as Larry says?  If not, why not?   I like Jeffrey's suggestion to use a little chalk on the post end to make moving it around easier.

 

And finally, if you have a top that has already been seriously dented inside from the top of the post, what works best to successfully remove the dents?  A little water to swell the wood, steam or ??

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