Insert Tooling and Cutterhead Balancing

Ways to balance your cutterhead when you don't need all four knives. September 17, 2008

Question
I just received some new cutterheads for my moulder that have insert knives like Tersa and the head comes with four knife pockets. I know I'm only going to get a single knife finish so I really don't want to run all four knives in the pockets if I don't have to and they don't have dummy knives for their heads.

So my question to the experts is after running the first four knives, do I just grind the edges down on two of them and make my own dummies, or will running four knives give me twice the run time before I have to change them? And if I'm getting a single finish then one of the knives is doing more work than the others, could I just change locations of the four knives into different pockets and get extended life out of them? Any help and advice would be appreciated.

Forum Responses
(Solid Wood Machining Forum)
From contributor J:
I would run them until they are dull, take two (opposite from each other) knives out, and just run two sharp ones. Make sure your gibs in the empty pockets are balanced and tight. You should be just fine.

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From contributor J:
One other thing - a lot of people recommend running the "dummy" knives in you empty pockets. I use filler strips myself. It is a good practice. But if you drop all the rocket science and have just balanced gibs, it has worked just fine.

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From contributor C:
You are right on target. Once you have worn out the edge(s) on your first set of knives, grind one pair's edge off completely and use as filler - just make sure you balance them after grinding. What Contributor J is saying is the same thing, just for corrugated head's, not insert style like you are describing.

I don't recommend running empty slots, especially on corrugated heads, which will warp if you run them tightened on only two pockets (if it’s a four pocket head). The other problem with leaving pockets open is they collect dust and pitch and resin, and can become unbalanced, affecting finish, as well as making it a pain to clean if you ever need to use the other pockets.

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From contributor C:
The dummy knives work great, no real need for four knives. Use old knives or dull ones and grind them down.