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Cutting Frozen Lumber

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Cutting Frozen Lumber

As wood freezes the water part becomes more important to the cutting. Cutting unfrozen wood is a matter of severing wood fibers. Cutting lightly frozen wood is a matter of cutting a slushy mix. Cutting thoroughly frozen wood is cutting hard ice reinforced with wood fibers.   

One of the factors that changes is the composition of the sawdust and the way it moves out of the gullet. A gullet that operates well in warm cutting will become overloaded in slushy cutting and then not be able to hold any material at all during frozen cutting. The sawdust changes from chips to slush to a very fine dust. 

In normal sawing you are cutting through a lot of individual strands. Once a strand is cut it doesn't hinder the next cut.  Cutting frozen material can be a lot more like sawing fiberglass. The material wants to grab the side of the saw. 

In frozen wood the saw makes a very fine dust instead of the kinds of chips normally associated with sawdust. This very fine dust does not load the saw gullet as does normal sawdust. Instead it can pass down either side of the saw. A saw is designed to have a loaded gullet while in operation to create dynamic tension that helps keep the saw running straight.  

Without the loaded gullet and with the extremely fine dust passing down one side of the saw or the other there is more pressure on the saw to move sideways. 

The most common solution to colder temperatures involves slower feeds and speeds. 

Another solution involves changing the gullet design as the temperature drops. At slightly colder temperatures the gullet is re-designed to more easily move the material out.  At coldest temperatures we are back to the original gullet design but there is an extra notch cut to trap the very fine dust. The notch creates a plug that traps the dust. The dust will build up and help maintain the dynamic tension.

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Tip loss can be a problem with frozen lumber. Tri-metal shims can give a significant increase in performance as can heavy duty wire solder. Tri-metal shims do leave a copper layer that has to be ground out when a tip is replaced but they do work extremely well. 

One filer said that the big reason for tip loss was too much tip exposure. If a normal tip to shoulder dimension is .032" then it has been recommended that perhaps a tip to shoulder dimension of .020" is more suitable for cold weather. This may not sound like much but it reduces the amount of leverage being applied to pry the tip out of the socket. The amount of force is directly proportionate to the length of the lever. This reduction in tip exposure means a reduction of approximately 35% in the amount of force trying to pry the tip lose. 

Another part of the problem is that tips don't necessarily get pried lose. Sometimes they shatter and it looks like the tip came out clean. Mills have successfully solved this problem by switching to a tougher grade of carbide.


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