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“Thicknessing” the Ribs

December 4, 2010

I wouldn’t have ever thought that “thicknessing” was really a word… but I’ve run across it several times now in books and online articles when referring to planing or scraping wood so that it’s a specific thickness.  So I’ll just go with it.  ;)

The goal was to take the rib pieces from their original thickness (around 1.8mm) down to as close to 1.00 mm as I could manage. In reality, though, the digital vernier calipers that I used measured in increments of .05mm. So I typically saw numbers like 0.95, 1.00, and 1.05mm.

It was very tricky to thickness curly maple!  Not so much because the numbers are so precise and small (although that has its own difficulties), but more because of the “figuring” of the wood.

Since the wood is “curly” (also called “figured”), that means that the fibers of wood wave back and forth (or you might say “up and down”, if you lay the rib piece flat on a table), instead of being straight/flat. (It’s a lot like curly hair vs. straight hair.)  If you’re not careful enough, you get “tear-out” of the wood, where the blade from the plane you’re using catches the fibers (instead of cutting them), and then where the fibers angle down, the wood separates along the downward angle.  Since it’s “curly”, though, the fibers change direction and start angling up.  So they tear out.  Basically you end up with little dips in your wood where the tear-out occurs.  If you have a sharp enough blade and if you use the right angle when you plane, the blade should cut through the grain, instead of grabbing it and pulling it along.

As an aside, I’m not sure exactly what causes the figuring.  My personal speculation is that it’s somehow caused by the twisting rotation of the tree as it grows (perhaps following the sunlight throughout the day?).  But that’s just a guess!  I really have no idea, but I’d love to know!  :)

 

I began thicknessing a set of ribs (three pieces) with a block plane (turned at an angle, up to 45 degrees from “forward”) and with the wood clamped to my work bench.  Right away, I was getting too much tear-out.  I read somewhere that one way to prevent tear-out is to get the wood wet.  So I got a bowl of water and a washcloth, and sogged the wood a bit (evenly, front and back, to prevent warping), and then started planing.  It seemed to work.  It prevented most of the tear-out, anyways.  When the wood fibers seemed to start catching on the plane again, I would get it wet again.  (But by then (when I was first figuring out how to plane the wood with this method) it was usually too late and the tear-out had already occurred.)

This wet-planing went really quickly.  But a couple of warnings:

  1. Don’t forget to dry your plane, when you’re done!  Else it might rust (even if you think it won’t!).
  2. The wood will actually change size when it’s wet.  The ribs, when they were wet, were wider by at least a few millimeters (which is a lot, in the realm of violin making).  I imagine they were also thicker when wet, as well, so you need to take that into account when measuring with the vernier calipers.
  3. The end result is kind of rough.  You’d still want to scrape the wood when the ribs dry.  It’s no where as neat and shiny as if you planed it dry.

Also, I still got some tear-out and the ribs in those places ended up much too thin.  So having a sharp blade is still important.

But in the end, though, I’m not sure you want to get the ribs wet like that.  I’m not sure what affect the water (and the wetting/drying process) would have on the final result, but I’m a little skeptical.

 

So I basically chalked up this set of ribs as my practice ribs, and I test things on these ribs, now (which have become really, really thin, as a result, and would never be usable.)

One of the things I tested, at someone’s recommendation, is setting the blade of the plane very, very shallow and making it very very sharp.  I tried that, and  I also tried NOT clamping the wood down, but holding it with my other hand (so that I could feel when it was about to tear out, better, and so that the rib would slip out of my hand rather than the plane tearing the wood fibers out).  It’s much, much slower that way, but the end result was really close to being amazing!  The only problem was that I still got some tear-out, even after that.  But the wood, where it wasn’t torn out, turned out to be as smooth as silk!  It’s really cool!  Unfortunately, though, part of the deal is that the blade of the plane needs to be really, really sharp.  So I needed to sharpen it again, before testing it on the next practice rib.  And then I needed to reset it back in the plane.  I was never able to get my other ribs as beautifully planed, after that.  :(  bummer.  I suppose with a lot more practice of sharpening and resetting the plane…..

 

Anyways, since that set of ribs was ruined (but not without benefit! I learned a lot!), I decided to try thicknessing a new set of ribs.  This time without water, and without using the block plane at all, and without clamping it down.  Things went much better once I figured out what would work.  The picture below shows the various tools I finally settled on using and their resulting wood shavings.

image

The below picture shows the tiny Ibex “finger plane” I bought.  (2 centimeters long, if I remember correctly.)  I also bought a “toothed” blade to put in it.  If you look closely at the inside part of the plane, you can see the “teeth” in this picture.  The teeth help minimize tear-out (but I’m not sure how).  They really do help!  But it doesn’t work perfectly.  You still need to be careful to avoid tear-out, and you still need to set the depth of the blade just right.  Trial and error…

The wood shavings are long and skinny and curly, after the first pass.  Kinda fun.  :)

image

I knew that often people use “scrapers” to remove wood when making a violin, so I’ve been trying to figure out what will actually work for me and what doesn’t.

In the next picture is a knife I found somewhere in my kitchen.  I think I got it from someone.  It’s not exactly a paring knife… maybe it’s a sharpened butter knife or something.  I’m not sure.  But it’s stainless steal, so it’s hard enough to use as a scraper (I’ve tried using aluminum.  no good).  I’m right-handed, and the bevel is on the “left”, while I’m scraping towards the right.  I alternate the angle that I hold the knife.  Sometimes I hold it so that it leans to the right and I scrape towards the right, but sometimes I hold it so that it leans to the left and I scrape towards the left.  The bevel is not equal everywhere.  It’s more blunt at the tip.  Again, trial and error.  I also found that turning the blade to an angle would sort of drive the shavings away to the side of the blade as I went, so I could go farther without having too many shavings in the way to see.  Plus, there was less possibility of tear out, I think.  And I had less of a “rippled/washboard” effect on the final product.

The wood shavings look longer than they really are.  The shavings compress into one another and result in a longer-looking, fragile, curly shape.

Interestingly, I think I was able to remove more wood in the same amount of time as the toothed finger plane.  But maybe if the toothed plane were the normal size of a block plane, that would work the fastest…  I’m kind of cheap, though, so I’m not sure I’ll buy such a thing to try it.

image

The “scraper” in the next photo is actually just a “painter’s knife”, which I found at an art store.  (I think it’s used for mixing oil paints…?)  I start by using it similarly to how I use the kitchen knife, above.  (although it’s more awkward to hold.)  It has no bevel (just a 90 degree edge), but is really thin and flexible stainless steal.  (A little less flexible towards the handle.)  You can see that the shavings are really small.

Sometimes I angle it towards the right, and then move leftwards with it.  I do that especially on places where I think the kitchen knife was too harsh on the fibers and started bending them instead of cutting them.  This method sort of seemed to undo the damage by cutting them from the opposite direction and possibly making them lay flat again.  Anyways, it brings the “shine” back again, where the wood looked a little rough.

Sometimes I brush it back and forth like a paintbrush to do some final scraping.  The result is more dust-like.

image

From what I hear, scraping the wood is always better than sanding the wood on the parts of the violin that go towards the outside (the parts that get varnished).  I suppose you don’t get the scratches left over from the grit/abrasive of the sandpaper.

I still wish I could have perfected the planing method that left the wood feeling as smooth and cool as silk, but this will have to do, for my first violin.  The thickness is really quite decent, so I don’t want to mess with it much more or else it’ll get too thin.

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5 Comments leave one →
  1. January 23, 2011 9:03 pm

    Nice work! Keep at it. It only gets more and more fun (and more addicting…..)

  2. Robert English permalink
    February 24, 2011 8:05 pm

    It’s wonderful work. I’ve just completed a kit fiddle from stew-mac, carefully thicknessed and it sounds great. Now I have the Henry Strobel book and am today cutting out the mold pattern.
    Regards from
    San Anselmo, CA

  3. Rob permalink
    May 27, 2011 10:52 am

    Thanks for sharing, Sarah. I have a violin that I started 2 years ago, but had to put on hold due to new job, moving across the country, buying a new house, trying to sell the old house, etc. You have inspired me to start back on my instrument. Good luck on your own instrument, and I hope you post again soon.

  4. September 16, 2011 3:19 am

    Dear Sarah I am not sure if you’re still following your blog but, I think your blog is inspiring. You should show us the finished work as soon! We are being unpatient :)

  5. June 21, 2012 7:00 am

    A suggestion made in The Art of Violin Making is to use a block plane with the bevel cut at 45 degrees (which you mentioned) AND cutting it so that the bevel is on top rather than on the bottom as is normal for a plane. This appears to give the plane more of a scraper rather than chisel action and is supposed to be much less likely to bite into the wood.
    Thanks for the tip on wetting the wood for thickness planing. I’d not heard of that before.

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