How to tell when insert cutters need to be rotated?

[Dan Friedrichs]

I have a J/P with carbide insert cutters. Is there any way to tell when they would benefit from being rotated to the "next" new edge?

I pulled one off, cleaned it, and tried to discern which edge was worn, but couldn't. All edges pare end grain about the same, they "feel" the same against my fingers, and are visually identical under 10x magnification. Yet, I've ran a lot of wood over this edge, and I would expect them to be a little dulled, by now.

[glenn bradley]

The darn things do seem to last forever. I rotate mine when they start leaving tracks on the material or when there is a noticeable effort to push material across the jointer very similar to when knives are dull. Of course unlike knives it takes a year and a half to get to that point in my shop.

[Jim Andrew]

I cleaned my cutter heads on both the jointer and surfacer about a month ago. Was a little worn that day, but still wanted some shop time. Used some LA awesome ammoinia cleaner in a spray bottle, and a tooth brush after letting it set for a minute or so. Cleaned up very well, then used water to rinse off the cleaner, finally blowing out all the water left over in any cracks, then running the machines for a bit. Cleaning makes my cutters cut like new. Clean my sawblades anytime they look like they are building up pitch.

[Bill Dufour]

Amp meter under load is the only real method, of course you have to first do this with brand new inserts to get a reference number to compare it to.

[paul dyar]

Bill you would also have to use the same with board and take the same depth of cut. I wish I had done this when I installed the byrd head in my dewalt 735. Maybe I will when I rotate the cutters.

[Jim Riseborough]

Amp meter under load is the only real method, of course you have to first do this with brand new inserts to get a reference number to compare it to.

It would be hard to notice much difference on a big machine. You would also need the exact same piece.

Best way is sound, and then finish on the wood.

[Wayne Lomman]

You won't know unless you rotate them as you don't have a reference point. Rotate them now. Use a black permanent marker to mark the edge that is used. See what difference it makes. The advantage of carbide tips is that you are not throwing anything away by doing this. If it turns out that it makes no difference it doesn't matter because you still have those edges to use in the future. Make a note in your machine records book so that you know when they were changed and why. Everyone keeps a notebook in the shop for recording machine maintenance, modifications, tooling, service data etc, don't they? If not, start doing this. It saves a hell of a lot of money and guess work. Cheers

[Bill Orbine]

These carbide inserts already have a marking on them on one corner. At least the shelix inserts do. I keep a log indicating the service and where the markings were before. I have two more edges to go on most of them. A couple have been turned again because of nicks. These guys last a long time.

As for when to turn the inserts, I go by sound. I've turned the inserts once even though the quality of the cut did not seem to have diminished but the sound was noticeably louder from when I first got my planer. This was after 4 years and running thousands of BF thru the machine. I'm not taking the risk of letting the inserts get too dull for that they could shatter easily. Especially with these screwed down inserts. I'm sure the amp meter would register more on duller cutters, but at what point before maximum load range would be too much for the cutters? Who knows? I rather not chance it. Not with a single insert letting go trashing up the rest of the head. No thanks.