Machining Problems with Red Pine and Southern Pine
Chipped or torn grain from moulder or planer knives in Southern Pine is related to an over-dry surface. September 6, 2011
Question
We are machining finger joint red pine into a 6 head moulding machine and we are experiencing substantial splitting and peeling. Heads number 1 and 3 are de-roughing the wood with helical cutters. The finishing is done with corrugated hydro heads. We have tried 12 and 20 degree angles without any success. Could the wood have been fractured during the blanking at the finger joint plant?
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Forum Responses
(Sawing and Drying Forum)
From contributor J:
Check your moisture percentage. I've had similar problems with pine/fir being overdried, or having shake (harvested from a windy area creating internal stress in the material).
From contributor D:
Looks like tear out from surfacing, not from the joinery.
From Professor Gene Wengert, forum technical advisor:
This is a common defect with red pine and southern pine. It is worse when the wood is under 10% MC. It is worse with aggressive cutting and high pressure feed roles and a few other items in the machine that exert pressure (even the lack of adequate clearance angle). In fact, this is why we seldom see these species used for quality furniture where there is a lot of machining. The defect is called chipped grain, torn grain and raised grain.
Check the MC whenever the defect occurs (not an hour or two later). Use a pin-type meter from a name brand company to make sure you get good readings. Measure both the surface, 1/4 deep and 1/2 deep. Oftentimes, the pine is dried by people that know how to dry studs, but not higher quality material. They do not know about equalizing. When drying is completed, the surface MC is often under 2% MC even though the average is 15% MC.
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