Debarkers: why?

Other Versions
Spanish Why debarkers are an essential tool in primary processing. October 15, 2001

Question
Could someone please explain the exact purpose (other than the obvious) of a debarker?

Forum Responses
From contributor B:
This sounds like a test. Well, the obvious answer is to take the bark off. This needs to be done because by the time a tree is felled, topped, skidded out, bucked up, loaded onto a truck, hauled over rural roads, dumped onto a log yard, piled and re-piled and then taken to the mill, it probably picked up dirt, grit, rocks and other foreign objects.

A sharp blade that hits just a spoonful of gritty dirt will have its useful cutting life shortened probably by half. If the blade hits a rock the size of a pea it would most likely need to be changed before productive and quality sawing could resume. If a larger rock, say the size of an ice cube, is hit, the blade would likely be ruined.

The debarkers, as used on a band mill, cut a narrow swath ahead of the band saw blade to remove the bark and hopefully the dirt, grit and stones.

The debarkers of this type use circle saw blades 4' to 8" in diameter and 1/4" to 3/8" wide. The carbide teeth used in these blades will better withstand the grit and stones.

Most people claim the use of the debarker will double the sawing life of a band saw blade.

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In addition, I think running the de-barker over clean bark extends blade life. I don't know if it is normal dust in the bark, or just the bark itself.

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From contributor B:
I’ve noticed that too. I’ve sawn shagbark hickory that never really touched the ground and I’d swear I’ve seen sparks fly when the blade hit the bark.

My son was cutting some soft maple from along a major stream. Although they looked clean, he dulled his chainsaw before he could get one down. He ended up taking an ax and cutting rings around the trees to remove the bark before he sawed into them. Another mill sawed them and they had to hand debark every one. After that, he got a debarker.

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The time saved by not having to clean the log ups production a lot. And the time saved by not having to change the blade as often makes more boards by the end of the day.

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Depending on the species and location of the mill, bark mulch can be a saleable mill byproduct. Debarking as a separate operation allows for the bark to be kept separate and conveyed to a collection point.

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The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
While it is true that debarking extends machinery life, the main reason for debarking is so that sawmills can sell chips from edgings and slabs to paper mills. Paper mills will not buy chips with bark. Without this market many sawmills would be forced to burn the edgings and slabs, which is a much lower value use than chips for paper.