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curling of wood


Ankit Gupta
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before some time when some renovation work was going on my house i noted that when carpenter was making the wooden bar plane and shiny by using his blade , every peel of wood was curled , can any body tell me why that was happened why they wasn't flat ?

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before some time when some renovation work was going on my house i noted that when carpenter was making the wooden bar plane and shiny by using his blade , every peel of wood was curled , can any body tell me why that was happened why they wasn't flat ?

 

Cool question. I don't know much woodworking but presumably when it gets stripped away by the planer one side of the strip is stretched longer than the other side making it curl.

 

The same thing happens if you've ever curled ribbon when wrapping a gift (the running it between thumb and scissors thing). Scientific American had a thing on that.

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Cool question. I don't know much woodworking but presumably when it gets stripped away by the planer one side of the strip is stretched longer than the other side making it curl.

 

The same thing happens if you've ever curled ribbon when wrapping a gift (the running it between thumb and scissors thing). Scientific American had a thing on that.

 

Except a ribbon will curve toward your scissors, while wood will curve away from the knife.

 

I imagine it has something to do with the way the natural fibers in the wood are agitated by the knife. Definitely a cool question.

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Except a ribbon will curve toward your scissors, while wood will curve away from the knife.

 

Absolutely. Metaphorically -- I should say -- your thumb in the ribbon example is the blade in the planner example. They stretch the fibers in each. The explanation in either case, I'm sure, is that you're stretching fibers on one side of the strip.

Edited by Iggy
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I' d propose the following:

 

A blade is an instrument that produces a deformation in the material, in opposition to a saw that is an instrument that removes material.

When the blade is inserted, the 2 parts of the wood are obliged to change orientation. In this case, one part is thick and changes not, the other is thin and takes all the deformation.

Since wood is a material aligned (not sure how to say that in English ) , it has a resistance that is not isotropic. Wood resists perfectly to traction & compression to a force parallel to its grain and resists poorly in the direction perpendicular to its grain.

When the carpenter uses its blade, it is always parallel to the wood grain (with the grain), the exerted force is perpendicular though and the thin peel of wood has absolutely no resistance to it, so it curls.

 

 

woodblade.jpg

 

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(edit)

Don't put the blade otherwise or it will enter the wood profoundly.

Edited by michel123456
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I' d propose the following:

 

...

When the carpenter uses its blade, it is always parallel to the wood grain (with the grain), the exerted force is perpendicular though and the thin peel of wood has absolutely no resistance to it, so it curls.

 

 

The carpenter often skews the plane so the blade is not perpendicular to the grain and in this case the curl comes out as a helix. Planing askew reduces tearout. Some planes have the blade skewed in the frame, such as rabbet planes which require the frame to stay parallel to the cut and which must also cut across the grain. (cross-grain planing does not make curls, rather it makes little chips.)

Edited by Acme
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Wood is compressible - you can dent it. The blade is not only stretching the bottom of the shaving as it cuts in (notice the slight stretch inwards as one cuts a tomato with a knife - the skin is stretched a bit before it gives) but compressing the top of the shaving by bending it upwards. Some of this compression, like a dent, is fixed in the wood. Stretch on one side and compression on the other makes a curl.

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