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Forum topic by ChuckV posted 08-29-2012 11:20 PM 1295 views 0 times favorited 32 replies Add to Favorites Watch
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ChuckV

2441 posts in 2223 days


08-29-2012 11:20 PM

My 8-year-old son was watching me lightly pare with a chisel today. He asked me, “Why do the shavings curl up like that?” I really don’t have a good answer, and “It’s the same as with the shavings from a plane” isn’t much of an explanation. I can imagine this happening if the fibers on one side of the cutoff piece are more intact and exerting more force, but I don’t see clearly what the cause it.

I’m probably missing something simple.

- Thanks

-- “While the world with closed eyes sleeps, The sky knows and weeps - steel rain. ” ― Nathan Bell


32 replies so far

View PurpLev's profile

PurpLev

8476 posts in 2345 days


#1 posted 08-29-2012 11:27 PM

the blade is slicing the fibers, and the movement of the blade forward is breaking and pushing them upwards (almost perpendicular to the bevel angle) the thinner the shaving, the less “breakage” and the more of a natural ‘curl’ is formed to the eye.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View hhhopks's profile

hhhopks

564 posts in 1074 days


#2 posted 08-30-2012 12:46 AM

If true, I should able to uncurl it make it stay that way. Right? But that’s not the case.

It is an interesting question.
I would need a more detailed sciencetific explanation.
Sorry, I am not offering any. : _(

-- I'll be a woodworker when I grow up. HHHOPKS

View Loren's profile

Loren

7746 posts in 2344 days


#3 posted 08-30-2012 12:48 AM

The wood is compressed by the cut and because the chisel
bevel forces it to go one way, a little extra compression and
breakage occurs on the opposite side, causing the curl.

-- http://lawoodworking.com

View CharlieM1958's profile

CharlieM1958

15706 posts in 2915 days


#4 posted 08-30-2012 12:52 AM

I would say it has more to do with stretching the fibers as you cut.

Did you ever see a person gift wrap a package and curl the ribbon by running one side of it against the sharp edge of the scissors? Same principle.

-- Charlie M. "Woodworking - patience = firewood"

View ChuckV's profile

ChuckV

2441 posts in 2223 days


#5 posted 08-30-2012 01:04 AM

hhhopks,

That is exactly what my son and I talked about. The curl is permanent.

Also, what determines the direction of the curling, i.e., clockwise or counterclockwise? Maybe it has to do with the direction that the blade is skewed. If I were in my shop now, I would try skewing in both directions as well as trying to cut with no skew and see if this affects the direction of the corkscrew. I would expect just a coil like a clock spring when cutting without a skew.

-- “While the world with closed eyes sleeps, The sky knows and weeps - steel rain. ” ― Nathan Bell

View rance's profile

rance

4143 posts in 1857 days


#6 posted 08-30-2012 01:05 AM

I think it has to do with the Coriolis Effect. Curls will turn the opposite direction south of the equator.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View daltxguy's profile

daltxguy

1373 posts in 2610 days


#7 posted 08-30-2012 01:09 AM

I’m going with a combination answer – stretching of the fibers from the blade – Charlie’s explanation is an easy way to explain it to an 8 yo. – but if the cut is reasonably thick, then I think there must be some compression too on the top side of the shaving caused by the plane ( or chisel) blade pushing the shaving away from the plane of the surface.

If you take an axe to a tree at an angle, the chip which comes out will be slightly curled – that’s not likely from stretching the fibers.

If you plane endgrain, does it curl?

-- If you can't joint it, bead it!

View ChuckV's profile

ChuckV

2441 posts in 2223 days


#8 posted 08-30-2012 01:10 AM

rance,

That sounds right. Now I remember learning all about this in Earth Science in the 8th grade.

I hope that the Curiosity Rover will be doing some wood curling tests on Mars.

-- “While the world with closed eyes sleeps, The sky knows and weeps - steel rain. ” ― Nathan Bell

View CharlieM1958's profile

CharlieM1958

15706 posts in 2915 days


#9 posted 08-30-2012 01:16 AM

Chuck, this is what happens when guys our age have young kids.

I’m glad mine are 26 and 23…. they already have ALLthe answers!

-- Charlie M. "Woodworking - patience = firewood"

View Porchfish's profile

Porchfish

577 posts in 1229 days


#10 posted 08-30-2012 01:37 PM

Wood Fairies !

-- If it smells good, eat it ! The pig caught under the fence is the one doing all thesquealing

View Bill White's profile

Bill White

3507 posts in 2657 days


#11 posted 08-30-2012 02:01 PM

Smart alec kid. Ban him from the shop. Shouldn’t be askin’ questions that the old man can’t answer.
Just jokin’ of course.
Bill

-- bill@magraphics.us

View ADHDan's profile

ADHDan

552 posts in 805 days


#12 posted 08-30-2012 02:55 PM

My chisel shavings never curl. They just come out straight as a board.

Clearly the answer is: you are a wizard.

-- Dan in Minneapolis, woodworking since 11/11.

View Surfside's profile

Surfside

3301 posts in 870 days


#13 posted 08-30-2012 04:34 PM

Chuck, why don’t you tell your son, “It’s natural son. Things happen on their own and they just happen. There’s no need to question them. Just like your hair, it goes curly as it grows longer.” Pretty effective for me. lol

-- "someone has to be wounded for others to be saved, someone has to sacrifice for others to feel happiness, someone has to die so others could live"

View ChuckV's profile

ChuckV

2441 posts in 2223 days


#14 posted 08-30-2012 04:44 PM

Sometimes I think I should be more like the Dad in Calvin and Hobbes

-- “While the world with closed eyes sleeps, The sky knows and weeps - steel rain. ” ― Nathan Bell

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Surfside

3301 posts in 870 days


#15 posted 08-30-2012 06:13 PM

Not if you don’t have a smart kid like that.

-- "someone has to be wounded for others to be saved, someone has to sacrifice for others to feel happiness, someone has to die so others could live"

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