Specialty Planer Heads

      Pros discuss the options and their preferences. April 10, 2005

I am shopping for a 20" planer and I am trying to decide if Tersa or spiral head with 4 side carbide inserts would be better. I am happy with a spiral shaper cutter that I am using for flush trimming. I assume that I will be able to achieve a chip out free surface at a higher feed rate on the planer with a spiral head. What is the down side? I have never used a Tersa head, so other than the quick change ability, I do not know the advantages.

I am looking at the SCM S520ES with a Shelix head versuss the S520ET with the Tersa head. If I decide on Tersa I would also consider the Griggio PSA 520. They are all in the just over $10,000 price range. Should I be considering some other machines?

We make custom doors and windows, materials ranging from Redwood and VG Doug fir to Mahogany and Hard Maple. Almost every surface that comes out of the planer will go through the wide belt sander before it goes out the door.

I imagine that the quality of the spiral head would have a lot to do with the quality of the registry on the inserts. How does Shelix stack up? I plan to convert the head on my Northfield jointer to a spiral head, a Drake Whisper Cut, supplied by Northfield.
Does any one have any feedback on Drake?

Forum Responses
(Solid Wood Machining Forum)
From contributor A:
I've got a Chinese version of the Strato planer, double sided 16" that cost $16k with spiral helical inserts. To date Iíve probably run 150,000 board ft. I have not rotated my knives yet, but the surface quality is unbelievable. My 16" planer is from Extrema.

From contributor B:
One thing to keep in mind is the sharpening process for Tersa knives is proprietary. They are currently charging a ton just to handle the knives. Then there is the sharpening fee, which is of great concern to us as we have 4 Tersas for our moulder, a Tersa head in our 24" planer and 2 joiners with Tersa knives. But, the cost of retooling is out there as well.

From contributor C:
Test side by side and you will find that the spiral cut takes less horsepower (amp draw) and produces much less noise. It is also less expensive when you dull the knives (inserts). The only drawback is the time to rotate all the inserts.

From the original questioner:
Is any one using the spiral head on their jointer? At an acceptable lever of chip out, to be cleaned up with a wide belt removing a bit less than 1/32", does any one have any comparisons on maximum feed rates, Tersa versus spiral?

From contributor D:
Iím a tool grinder for Omega Cabinets and we've tried both on the #1 spindle or hog head on our moulders. The moulder guys would have problems with the Tersa heads chipping out because one or two knives would lock into place and the others wouldn't which caused uneven knife height. The spiral head that we switched to they love, very low maintenance, maybe once a month, to rotate inserts.

From the original questioner:
To contributor D: What brand of spiral head are you using?

From contributor D:
We are currently using two brands one is made at WKW and the other is made at North American Tooling. They both use the same type of inserts, 15mm x 15mm x 2.5mm. We do have some that take 14 x 14 x 2mm but they don't last as long.

From contributor E:
We have had a 24 inch SAC planer with Tersa heads for about ten years. We also have a 20 inch Martin Joiner with Tersa. We have never experienced the imbalanced knives. We do, however, have some serious problems with noise. Is it possible to convert these heads to spiral? How much would it cost?

From the original questioner:
To contributor E: I think the answer is yes. Byrd Tool could supply you with heads. I am trying to determine the pros and cons of the Byrd head. A machinery supplier in CA had some issues with the Byrd head and decided not to offer it on there machines. They claim knives would break on heavy cuts over 1/8" and some times it was difficult to realign the replacement knives. I talked to a fellow with an import double sided planer with spiral heads and he said that new the surface was great, but once he rotated the insert knives, lines appeared on the wood.

Laguna Tool in CA is working on a spiral head with spiral Tersa type knives. They hope to have the first one in there shop the end of this week. I am curious to hear how this tests out with regard to noise, chip out, and feed rate.

I have asked the folks at Byrd to give me the names of some people who have been using there head for a while, both jointer and planer to see how they like it. Other manufacturers may be offering heads like this that have solved the problems. So far I do not know of any.

From contributor C:
Precise planing or jointing with any head requires the knives to be set correctly. You and I can feel less than .001" with our thumb. I noticed a comment about lines with an insert head after changing inserts. When changing inserts on any head, the head pocket must be clean with no burs in the pocket that would cause the insert to not set flat or shouldered up against the location points. If the insert head worked properly when new, the alignment factors should be there. Someone put the inserts in to start with and they worked correctly. The insert heads are not sharpened after the inserts are attached so the principle must be there. The other factor with the insert head is the replacement inserts. Are they the exact same dimensions? The angle and physical size must be the same if replacing just a few inserts. Original parts will only match old inserts. If you change brands of inserts, change them all.

From contributor F:
We are running Tersa Heads in a S4S machine, jointer and planer all Martin. I have never experienced problems with imbalance or high knives. When setting these knives you have to run a piece of hardwood to seat them. Softwood does not do it. Keeping the heads clean is important also. Tim, we have no issues with noise. The planer and S4S are soundproofed very well and do not make noise till the knives are very dull. I think spiral knives are quieter than straight knives. Changing the cutter head in a Martin machine would be asking for a lot of trouble in my opinion.

I think there is a lot of pros and cons to each type head with no perfect solution. In our shop, determining the success of cutters comes down to two things - quality of cut and labor costs to change the knives. Tersa meets these needs. Also the type of timber you process would have some influence on the choice. We run a mix of hardwood and softwood, both knotty and clear. Because of the thinness of knife, Tersa does not hold up well on wood like recycled White Oak. They do work well on recycled heart pine as long as the wood is clean. We are just starting to experiment with carbide Tersa knives on part of the jointer head. They have not been in long enough to tell if that is better than M42.

From contributor E:
To contributor F: What do you mean by running a piece of hardwood to set the knives? All we've ever done is assume that centrifugal force was doing this for us. What does the hardwood do? Is poplar hard enough?

From contributor F:
The need to set the knives is very obvious at the jointer. If you do not set them, your jointer will not cut true till many boards are passed over. After turning or changing the knives I usually find a piece of hard - hardwood like oak or maple and face this board a few times across the width of the knives. On the Martin jointer you test the setting with a well planed board about 1 meter long. Lay this on the out feed table with a little bit over the head. Rotate the head by hand and it should nudge the board about 1 - 2 mm each time a knife comes around. This also tells me if one knife is still high. If so, face with the hardwood again. With the planer and S4S if you do not set the knives your first few boards out will be a little thinner. Poplar and softer wood would eventually do the same thing but would take several passes.

From contributor G:
I've had a S520 Tersa for a couple of years and though I think the cost of the knives is out of line with reality I like the fact that I can change or shift the knives in 5 min or less. As far as noise the SCMI is a lot quieter than the Delta that it replaced. The repeatability is worth the cost to me.

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