Troubleshooting Carbide Insert Cutter Breakage

In this case, someone probably hit a nail. But the discussion includes a useful list of possible causes to investigate. February 9, 2008

I am having problems with Byrd T&G knives breaking. Every 3-4000 lineal feet one or more blades break. I have checked to make sure that they fully seat and I do not seem to have any vibration. Does anyone have any clues?

Forum Responses
(Solid Wood Machining Forum)
From contributor R:
First thing I would do is call Byrd.

From contributor J:
My guess would be you are running an economy steel on a very hard wood? If not, then maybe Byrd has a bad batch of steel - knives generally do not break!

From contributor J:
I use Byrd's T and G flooring set also, for machining hardwoods such as ash, oak, maple, cherry and walnut. My carbide inserts seem to last forever, if they don't hit metal. These inserts, however, do not like to run into metal that is found in reclaimed lumber, which we run on a custom basis for a couple folks. They break, and we charge the customer for the knives and time lost. Oh, and we run these on a standard five head moulder. Are you using carbide or steel?

From Dave Rankin, forum technical advisor:
As a general comment, if carbide inserts break, you need to look at a few things:
1. Proper seat in the head body. I have had brand new tools where the seat finish was not very good and this caused the carbide to not be stable; result was broken inserts.

2. Proper cleaning of the pocket in the head.

3. Proper tension of the gib. I have had many inserts break from incorrect gib tension. Too much pressure can break the insert during installation and not enough tension can allow the insert to vibrate during production, resulting in breakage.

4. Low quality carbide blanks. This is something that seems to come in spurts. If one of the carbide manufacturers has a problem in production, we will see an increase in breakage for a short time.

5. Material being run. As was stated earlier, contamination in the material can cause breakage.

From contributor M:
Thanks. After checking some of the flooring and looking at a knife that was not broken, I found that my denailing crew has a quality control issue. One of the knives that was not broken has a very suspicious hunk knocked out.

From contributor T:
Sometimes when an insert is broken during the cut, it will damage the seat of the head at the outside diameter. This can leave a very small high spot in the seating face that will cause insert breakage until it is ground off. You can send the head back to the manufacturer or any good tooling company to have it repaired.