Troubleshooting Side Tear-Out on a Five-Head Moulder

Tips on preventing tear-out in a moulder. January 2, 2012

Question
I just milled 1600lft of yellow poplar s4s through my 5 head Weinig moulder. Now moisture content was 8-9 for most part. I put in brand new re-sharpened side knives that are grinded to 20degrees. These are made of black nitride steel. Now as I am running this, I am noticing a lot of tearout on my sides. What can I do to stop this from happening?

I see every once in a while when running casing and base but this seems like it was tearing out a lot more than I usually notice. Sometimes it’s larger tearouts and multiple times on only one side or the other. Now I have to run more to cover those that are really bad. I need some advice.

Forum Responses
(Solid Wood Machining Forum)
From contributor A:
I just switched to a 12 inch knife pocket or head. Re-sharpen your knives and that should fix the problem 95% of the time. When I would have extremely stubborn tearout problems I would joint the knives, but then run at regular speed. I’d do this for lacewood, curly maple, and etc. The jointing thing works like magic, but you do sacrifice knife life and you have to grind more off when re-sharpening.

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From contributor J:
You left out an important point, which could be the sole cause of your issue - feed speed? The sharpest knives in the world will still tear poplar to shreds if fed too fast. Also, the grade of the board and quality of the grain plays a large role.

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From Gene Wengert, forum technical advisor:
Moisture content is a huge factor - too dry means more chip out. Knife angles are also important. We want an angle that makes the knife more robust rather than more slender. When chip out occurs, immediately measure the MC with an excellent moisture meter. Because pin meters do not go under 7% MC very well, you need a pinless meter.