Planing "Dimples" in Soft Lumber

      Planer blades can drive chips into the surface of a board when dust collection isn't perfect. Here's a good example with photos. May 21, 2009

Question
Is there any solution to these freckles I get after planing this beautiful old growth WR cedar? I get them even with brand new planer blades. Light sanding doesn't get rid of them, as you can see on this pair of double gates sealed with Penofin. Doesn't happen with every board, and I've even tried switching board feed directions when it does happen. What in the heck is causing this? Would a set of spiral cutters help?


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Here's a closer look...


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And here it is unstained. Looks almost like tearout.


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Forum Responses
(Sawing and Drying Forum)
From Professor Gene Wengert, forum technical advisor:
What you have is an inadequate dust system and that is letting the chips stay on the knives rather than being sucked away. The defect is called chip marks. The pictures are a perfect example of this defect. What happens when the chip stays on the knife is that it is slightly imbedded into the surface. This creates a dimple appearance (or as you call it, a freckle). Because the compression went several 1/100 deep, it cannot be easily sanded off with light sanding.



From contributor J:
What Gene said. I have a lot of reclaimed wrc like that. It's beautiful, stable, light and strong, but very soft - that's why it's easy to get this defect. A wide-belt sander will take care of it quickly.


From contributor S:
Yep, that's what they are. I found that I could do better by letting the planer run lightly loaded with no dust collector. Then the chips were easily thrown out of the machine by the planer head. I have not found it a problem to remove any marks with a sander either.


From the original questioner:
Darn, time to improve my dust collection setup then. At least replace the 4" flex hose I'm using now. I would've never figured this out (been scratching my head over this for months). Thanks so much for solving the mystery!


From the original questioner:
I haven't had much need for my planer these last few months but I'm still working on solving my chip dent problem. I called the Powermatic folks and got some good advice on what might be causing it. He said it was maybe static electricity in my 4" flex hose reducing the airflow. Told me how to wrap the wire inside and outside of the hose, grounding it at both ends. Before I do that, I thought I'd ask here if static electricity can reduce the airflow enough to matter? Also, is my 230V 2 Hp collector big enough when running only one machine, and 20' of 4" flex?


From Professor Gene Wengert, forum technical advisor:
Yes, I believe it can. But you may also have lost suction due to other problems, such as a clogged filter or bag, or poor design within the machine so that chips are not easily removed.


From the original questioner:
Okay Gene, I'll go ahead and ground that. Don't know when I'll next be planing anything, though, in this economy.

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