Running a Moulder with One Sharp Knife and a Balancer

One knife on a moulder head can do all the cutting, but it's a tricky arrangement to set up right. November 12, 2008

I'm running a non-jointed moulder with an insert cutterhead making door rails. I had a theory that if I replaced two of the cutters with resharpened ones and used one new insert to make the finished cut, that this would be better than using three dull knives. Would this work? And if not, why? I'm going off basic moulder knowledge that only one knife makes the finished cut.

Forum Responses
(Solid Wood Machining Forum)
From Dave Rankin, forum technical advisor:
What you are asking can be done under certain conditions. I am not a fan of doing this; however, the process requires that the two dull inserts first weigh the same as the sharp insert and second that the dull inserts be at least .005" shorter than the new knife.

Moulder operators have used 1 knife and a balancer for years with good results. Balance is critical and the need to have the "non-cutting" knives short enough to not cut is required.

For example, on my Terminus heads I run 2 knives and 2 fillers. The fillers are nothing more than HSS straight knives that have been ground back to be out of the cut.

It should be noted that when you run only one knife as you are asking, you will put some additional load onto the spindle and its bearings. I would not recommend using only 1 blade on any cut deeper than 1/2" or 12mm.

What I would recommend is having the inserts sharpened once as a set and reusing them. This works very good on most profiled insert heads.