Problem with Insert Tooling Teeth Breaking

A shop owner tries to figure out why teeth in his helical insert planer heads keep breaking (which leads to further problems and headaches). October 19, 2013

(WOOWEB Member) :
I've been running into a lot of trouble with my old Powermatic 20" planer that has been outfitted with a Byrd head. I've heard about how great these are for edge wear, but my teeth break constantly and then take out 20 other teeth when the carbide bounces around inside the planer. I spend a good half hour hunting down the offending chipped teeth, and some seem to break a few more a little while later. It's a chore. Is this common? It's most common when a knot gets pulled loose. It would be nice to run knot free lumber, but this is the real world. It's very expensive and time consuming to break 3 teeth and rotate 20 for every knot that comes loose. I'm thinking the best solution is to switch to a straight knife machine with built in grinder?

We are a small sawmill/mill works shop that planes hundreds of board feet at a time. I love the wear properties but the brittleness is killing me. Anybody have experience with this? Oh, and one more thing - the journals are getting chipped up as well and often have to be repaired with a file so that any knick left by the exploding carbide insert is smooth and doesn't crack the replacement.

Forum Responses
(Solid Wood Machining Forum)
From contributor J:
I installed the Shelix on my PM24 almost 4 years ago. I damaged 3 or 4 teeth once when I hit a hard knot (hickory, I think). I had to rotate several teeth and replaced 2 or 3 others that I felt were too damaged to use. That is the only time I've had any problems. It sounds like you are running mucho lumber through the planer.

From contributor T:
Could the knives be poor quality? I fitted a Byrd shelix head to my jointer. I thought it was fantastic until I had to rotate the knives and got witness marks which I couldn't remedy. I had to change back to my old straight knife HSS block. I never had the problem that you talk of.

I've got some Caster blocks supplied by Oertly on another machine which are very good.

From contributor K:
If you're breaking carbide inserts, get different brand inserts. As far as witness lines, that's because the saddle was not clean when you turned the inserts. Be clinical clean when turning inserts.

From contributor M:
Amen on cleaning the seats, and don't ever over torque them when installing inserts. Could that be part of the problem?

From contributor C:
Contributors M and K are right on target with cleanliness being essential to proper insert knife replacement.

Here is what Byrd recommends on replacing the inserts:

When replacing or rotating inserts, the seat should be as clean as possible. This will prevent breakage of inserts and ensure proper insert alignment. To properly align the insert, press the insert away from the seat while tightening to approximately 55 inch pounds torque. This allows the countersink in the tip and the taper of the head on the flathead screw to slide the tip into its proper position.

Also, we offer inserts made in Germany for specific use on the Shelix heads. They may be a little more expensive, but taking into account how long it takes to replace inserts, it is usually the more economical way to go.

Note: The Shelix heads use a special 15 x15 x 2,5mm radius insert with the insert radius being 100mm. A number of other heads use a more standard insert which is the same size insert with a different 150mm radius. Use of these 150mm radius inserts could also result in improper insert seating and the resulting breakage you're experiencing.

(From the original questioner) :
Thanks for the responses. I've been running this planer for about 6 years so it's not a day to day problem with turning or torqueing the inserts. If I'm running select cherry I'd say it would run forever with no problems. The problem lies in knots that pull loose. I am extra careful not to run things with loose knots but this planer tends to pull things out that I wouldn't call loose. When the chunk of wood pops out, the pieces bounce around. I've read where you need to watch out for loose knots, but that doesn't inform you what to expect in a day to day operation. Each pulled knot takes us down for an hour or so, replacing and cleaning broken and chipped teeth, firing up, finding more problem teeth, fixing those, etc. It's not something discussed much. Maybe it's just a trade off in running carbide - it's brittle. It could be the quality of my carbide. I emailed the company to see if they have any hints.

The teeth are very exposed on this type of journal. I've seen pictures of different styles and some have the tooth buried in the journal with only what appears to be the cutting edge sticking out. I'm wondering if this exposed Byrd style head has something to do with the broken inserts bouncing around and taking out a whole mess of others. The industry could not be running these heads in their giant machines with the trouble I'm putting up with, because knots pulling are a fact of life.

Anyone here have experience running a planer with a built in grinder on straight knives? Wondering if I would have less downtime?

From contributor D:
Cheap carbide? Seating, torquing. Yes, yes, and yes. We've run a good bit of knotty alder over the years and haven't had carbide inserts breaking. We even ran one planer once because we were so busy until it was dull as a butter knife - kept tripping the breaker until we broke down and serviced it. I have noticed, doing the maintenance myself on three planers for the past ten years, a few missing inserts here and there, and broke a few over-torquing them on scaly seats as well.

From the original questioner :
Wow, that's the kind of info I was looking for. It may be cheap carbide. I have to say I did start off buying from Byrd and when I switched to a different company they still had the same "BT" stamp on them, so I thought maybe they were just buying them in bulk and were the same thing. I'm talking to the guys who sell the stuff now to find out. Was your planer a Byrd brand or a Tersa type head? The Byrd inserts look more out in the open and maybe more prone to getting busted while the Tersa are really set in there and look protected. Maybe it's not that big a difference. It was just a thought from looking at pictures. The big double sided production planers carbide is really deeply inset and look like the Tersa style.

From contributor D:
No discernible difference I can tell between brands - one Byrd and two generic Chinese here. A good habit is to really clean the head well and properly torque the inserts. Those torque settings on a cordless drill you can get close by breaking one torqued with a torque wrench. Makes a great speed/torque wrench, and you can chuck a wire wheel in it to brush the head clean. I keep a permanent marker handy and mark every used/dull edge on the bottom as I remove them, so I don't accidentally reinstall them with a used edge. If you miss one, and can't tell which edge is sharp or dull, a sure method is to make a scratching motion with your fingernail. A sharp one will slide smooth, a dull one will have tiny fractures you can't see, but the jagged edge will be felt. Sometimes heavy pine resin buildup needs to be cleaned, and soaking in solvents sometimes removes my marks. Not a perfect method, but stuff has to be clean. Just loosening and rotating an insert may be causing problems. A tiny bit of debris under an insert will affect your finish, and eventually cause it to break, if it doesn't snap right away when tightening.

From contributor T:
Oh dear, we have talked the topic of helix blocks and Byrd tooling to death in this forum, but I can't find the related thread where we put it to bed. I took photos of the seating on my shelix, which I felt were very poor. For a comparison I did the same with my caster bocks which had perfect seating. If poor seating has anything to do with the problem, I would point the finger at the design of the block. If you remove one of the inserts from the shelix, you will see that there are only two small contact points in the seating that attempt to align the insert knife.

From contributor D:
Perhaps my tolerances aren't up to your specs. Maybe you expect a perfect finish. We all would. I remember your posts, and also remember thinking you may have had a cleanliness/seating problem. That was long ago and I thought you were good to go. Maybe not so. Honestly, I couldn't even guess why you still have witness marks, because our final dimensioning is done on a widebelt sander. Byrd heads are, in my opinion, not at fault. The only thing that can cause such a mark is a high knife/insert. Happens when crap, however small, is underneath, or a chip/defect/seating problem exists.

From contributor T:

Byrd's tolerances for the overall head are great; my shelix fits in my machine fine. There is no vibration; it's really good in that respect. It's the seating that I have an issue with. There are only two contact points to align the knife instead of a nice continuous seat which contacts the knife across the whole of one side like on my caster blocks. I get no problems whatsoever from my caster blocks, so I can dismiss the idea that I'm getting debris behind the knives. I would really like to be able to use my shelix again if the witness marks could be solved, but I can't see how it can. It was brilliant for the first 9 weeks of use with no witness marks at all.

The strange thing is that after rotating the knives, I could set the shelix up to give a nice flat unmarked surface, but after a few hours of use we would start getting witness marks again. The knives must have moved in their seats. This makes me think the seats are not suitable, but then again I had no trouble for the first 9 weeks, so this indicates the technicians at Byrd must be fitting the knives differently to me and my staff.

Is it possible you could make a video of how Byrd installs these knives so I can see where I might be going wrong?

From contributor D:
Maybe someone from Byrd tooling will chime in - I'm just one of many satisfied customers. That is strange, working for nine hours or so. These marks aren't bumps instead of dimples are they? That would indicate a chip in an insert.

From contributor D:
Confusion in the above comments - my tolerances I referred to were the expected finish on the wood, not the head as if I had manufactured it. Sorry about that. Yes, nine weeks (not hours) is actually not abnormal - we run ours three months or so. Perhaps if your Castor head is performing much longer in the same circumstances, that is valuable information for us all.

From contributor T:
My castor heads are not being used in the same way as my shelix was. With my castor heads I can rotate the knives once and there will be no witness marks because the seats align the knives so well. With the shelix I had to spend time adjusting the knives over and over again until the witness marks disappeared and then they would come back anyway. My problem wasn't down to chipped teeth, my problem was down to the knives not being aligned properly. I know that at least one other member in this forum had the same problem as me. Anyway, I'm trying to say that poor seating could contribute to knives breaking.

From contributor D:
I can feel the poor seating, but we still get great performance. Curious though, you say you can reseat them with better results. All this and the insert has a radius on it (4 inches). I have never had to reseat inserts in ten years. Every time the inserts are changed/rotated, I've gotten silky smooth wood coming out. The contact points you mention may not be sufficient for your application. Machining everything from pine to white oak daily, we get no broken teeth, and no witness marks until at least 9-12 weeks (and from chipped/missing inserts at that). We keep running them longer even, final dimensioning with the widebelt. Only other thing I can think of is maybe taking too much of a bite, or poor dust collection.

From the original questioner :
I talked with the folks at Global Tooling where I bought the original inserts. I've tried both their inserts and Byrd inserts without really being able to tell a difference in brittleness, but the new Global inserts that are coming out are supposed to be a lot tougher and may give me the impact resistance I need. Worth a shot.

From contributor F:
I am wondering whether anyone has had problems with inserts cracking due to differences in the thermal expansion of carbide and steel after leaving a shelix head outdoors over the winter. Temperatures get down to 10 below at times here. The last time I used my planer the teeth were perfect. I had just replaced a couple of broken ones and all were good. The planer sat out in the cold all winter and today, I went to plane something and many - like 1/3 of the teeth - were broken and pieces of them were on the planer bed just lying there.