Does Helical Insert Tooling Create Glue-Ready Edges?

      A shop owner asks about helical insert jointer knives for edge jointing, and sets off a long and informative discussion about the comparison between high speed steel, carbide knives, and insert cutterheads. April 18, 2015

Question (WOODWEB Member) :
I've used for many years a Powermatic 8" jointer with standard HSS alloy knives. I sharpen them myself and get very good results on both face jointing and edge work. Problem is, I use a lot of curly sugar maple and curly cherry, really wild stuff and it just beats them up in a hurry, to the point where they just won't put a clean edge on anything at all after a while. The issue isn't tearout, it is wearout. If I worked mainly with unfigured cherry, oak, walnut and etc. they would last for quite a while, but with the real wild stuff they go south really quickly. If I do a big job with a lot of crazy curly maple I may end up going through two sharpening/knife setup cycles on one job. It gets old and I need to reduce the amount of time I spend on this.

I am thinking of switching to a Byrd head. I am familiar with the complaints about the fine lines, etc. that need to be sanded out (who goes right from a surfacing tool to the finish stage, anyway), and I know it will never produce as sweet an edge as newly sharpened HSS, but what I am concerned about is the quality of the cut for edge joints that are to be glued for panels. Is the cut clean enough or is does the carbide pound the wood so much that the pores and cells are smashed to the point that it degrades the performance of the joint?

Forum Responses
(Solid Wood Machining Forum)
From contributor C:
I love the 15" Byrd head that I have in my Delta planer. Cut quality is more than suitable provided you plan to lightly sand parts. Tearout is minimal but don't expect perfect results, especially in woods like birdseye maple. Itís still substantially better than conventional knives in this regard. Having run thousands of board feet through mine, the inserts in my planer still cut like new. They hold up well to occasional glue, knots, etc. There will be very slight lines/ridges in spots but these are quite minimal if the head is setup well, and there is no dust/debris beneath the inserts. I have not found them to be an issue and they disappear almost instantly when sanding. This is a far better tradeoff than dealing with major tear out. That being said if you want to finish straight out of the planer like some people do conventional knives might give you a slightly more attractive surface. Go find somebody who has one of these, and see the finish in person if you are feeling picky. In regards to the jointer, in my opinion skip the shelix head on your jointer and go with a cutterhead that takes conventional indexible knives, something like a Tersa head. I also have a PM 8" jointer that I upgraded and while the helical carbide head is ok, I greatly prefer regular knives for this application. I find I get increased feed resistance, and I have to cut slower than usual to get a good finish.

From contributor D:
Do yourself a favor and order a set of carbide tipped knives from GG Schmidt. Skip the Byrd head on the jointer.

From contributor H:
I second the solid carbide knives.

From Contributor B

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One caution with the Byrd shelix head - it will rob you of horse power. I put one on my 12" Powermatic Model 100 planer about a year ago and we immediately experienced a significant reduction of cutting capacity. A planer that is rated and always cut 1/4" deep on 12" poplar would now barely cut 1/8" deep. Just today I finally made the change from a 3 HP to a 5 HP motor on the planer. This should solve the problem. The cause for this loss in HP is that a 3 or 4 knife head has a recovery space between each knife strike for the motor to recover from the power drain of the knife strike.

On the Byrd shelix head the carbide cutters remain in constant contact with the wood as the head rotates. There is never a break point between knife cuts for the motor to recover. There is in effect a constant drag taking place as one knife to the next makes it's cut in the wood. I don't recall if the Powermatic Model 100 planer was originally available with a 2hp/3hp option or a 3hp/5hp option, but I bought this machine new about 25 years ago with the 3hp motor. Over the years I had experimented with a 5hp motor on it but eventually changed back to 3hp as I felt the 5hp just wasn't necessary. That has now changed due to the Byrd shelix head. Other than this I have no real complaints on the Byrd cutter head. In the year since I made the change I've yet to rotate the knives. My old steel knives would have been changed out at least a dozen times.

From the original questioner:
Thanks for the responses. I can live with reduced power. I hear that a lot, even though the manufacturers claim that the spiral cutters require less power. Surfacing speed is not that critical to me, reduced downtime and tearout is far more important. I also have the model 100 planer w/3 hp single phase motor, and I think a 1/4" cut would really be pushing it. In any case, this is for the jointer, which I use for face flattening and edge jointing for gluing. That is my concern, what is the quality of an edge joint as far as gluing properties. I have gone straight from the hss knives to edge gluing for 20 years with no problems, and my concern is that as the carbide wears the ability of the cut to glue properly will diminish. I will probably try the shelix head. The curly woods beating up the knives is the major bottleneck in my studio.

From contributor X:
I use a Byrd head on my planer and shaper and they are great. Thereís no tearout at all but I would be hesitant to use them for edge gluing because they produce a glass like surface, which would concern me about getting a good glue joint, especially on dense woods like maple. Personally I like saw marks on my glue joints.

From contributor J:
I have a set of straight carbide knives that came with my planer and see alternate use with HSS knives. The carbide doesn't give quite the fine finish as fresh steel, but maintains a good finish for far longer. I would say that for jointing the carbide would be fine and considerably less cost than a Byrd head. The carbide lasts at least 3-4 times as long before re-sharpening. Connecticut Saw and Tool has reasonable pricing on sharpening carbide.

We use a Tersa head in our main jointer at work, which does a great job with five minute changeovers, but the knives seem to wear more quickly than standard HSS knives. We do a variety of work including using recycled wood, so the quickly replaceable Tersa knives are a great advantage when there is a risk of hitting embedded grit or metal. My understanding is that changing out the cutters in a segmented head is an infrequent but time consuming and meticulous job (although you should be able to swap out one or a few cutters quickly in case of hitting something small).

From contributor C:
If youíre using figured tearout prone wood mostly, a helical head is your only choice unless you intend on removing mass amounts with a sander to finish out. I prefer the finish of straight knife. So tersa was the only option that produced really good finishes for me. I have a tersa in my jointer. The big cutter head and slow feed rates do as good if not better than a byrd head would.

I would not worry the mini swales left by the byrd as far as edge gluing goes. Glue usually recommends .003 for glue, if anything the byrd will give you micro-relief in the joint to hold the glue and probably increase joint strength. I kept my 15" planer with byrd to accompany my 20" tersa planer - really the best of both worlds. I use heavily figured material regularly. If sharp knives with the tersa will not cut it I can just run it through the byrd machine. Finish with straight knife largely depends on sharpeness, feed rate, and skew. The tersa is so fast to switch out I use new edges for finish passes and use less than new knives for general stock removal. Then I use some beater knives just for material that may have debris hidden in it. It's longer to wait for the head to stop spinning than to swap out the knives.

The tersa knives will last just as long as any HSS, but as the poster above mentioned, if your milling reclaimed timbers then they will not last as long, but what will? My main concern with finish edge jointing on a helical is how are you edge sanding wider material that can stand on edge in your sander. The profile left by a Byrd, for me, was more than I liked to hand sand. To me it added more work than a straight knife, but was essential in some applications, not most. It sounds like your hoping to upgrade your current machine for a few hundred bucks more than thinking of purchasing a few thousand dollar replacement so I would certainly buy the byrd, it will be night and day for you. Make sure to start at the beginning and re-calibrate the entire machine and you will be happier for it and replace your bearing at the same time.

From the original questioner:
I purchased the Byrd head and after a few months and a few hundred feet of curly sugar maple and other stuff I will not be going back to the HSS knives - these inserts just go and go. Replaced the bearings and calibrated the setup with a dial indicator and it is truly sick how accurate and flat the boards are. I thought I was pretty good at setting up straight knives after sharpening and was always happy with the flatness, but this is another level of accuracy. Yeah, it was $480 but I will recover that in a year from time not spent fooling around setting up knives every week.

Tearout, sure, there is some on real crazy grain or extreme reverse feed, but overall it is not an issue. Much less than even with newly sharpened HSS knives. Feed rate, maybe some, but unlike some who responded to my original post, I never really push the machines real hard. I am a one person operation and speed/volume is not such an issue as it might be for some. If I was running hundreds of feet a day it might be an issue. So far, after much testing, I see no issues with edge joint quality. I can't get the joint to break before the boards do. The little swales are no issue at all and sand right out.

As soon as I see clear to do it I will probably get a Byrd head for my Powermatic 100 planer. It is a chunk of change, but it really is such a pleasure to just keep working and not have to deal with the knives. I have never really been a toolhead. I buy what I need and learn to maintain them but I'd rather spend my time cutting wood than adjusting machines.

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