Helical Cutterheads and Clean Gluelines

      Will a helical cutterhead leave little lines that may compromise glue joints? Professionals discuss finish quality, sharpening, and setting. March 26, 2007

I'm looking into putting a helical head into our jointer, but am worried about the smaller blades leaving small lines due to even a minimal difference in height when putting in replacement cutters. We do a lot of face to face gluing of solid wood and even a small line above the surface could create a bad joint.

We have a Terminus head now and are not too happy with it. Blades dull too fast and angle of head doesn't seem to be same as compared with the other cutter head. Any insight into the helical heads would be appreciated.

Forum Responses
(Solid Wood Machining Forum)
From contributor J:
We played this game before. Right out of the box, you can't beat them. If you replace the inserts yourself, you are most likely to get those lines you are talking about no matter how careful you are inserting the new ones. If they can be resharpened on the head, then you are in good shape again, but most companies will only sharpen those once or twice depending on the condition. Plus it is quite costly.

However, before you give up on the idea, see for yourself. Even with the lines you should get a decent glue joint. The lines are visible, but face gluing, I don't think it would be a problem. Especially if you replace them all at the same time.

From contributor U:
I think it depends what type of woods you are surfacing. Very hard woods will get thicker glue lines if there are slight ridges, while softer woods should not have a problem if clamp pressure is adequate.

I have a Byrd head on my planer, and just ordered a custom Byrd head for my facing jointer. I got better results - less noticeable line pattern - after I rotated the inserts myself. Getting the remnants of machining dirt off of the seats made the difference.

My edge jointer still has straight knives, but even there, you get some very light scalloping due to the cutting circle, especially if you feed at a decent clip. This doesn't seem to affect the edge gluing.

From contributor M:
I'm running Byrd Shelix heads on both the top and bottom heads of my moulder (as well as side heads) and I don't have any problems with gluing up faces coming out of the machine. I too had to reseat some of the inserts in order to get a good surface, but it was still well worth the effort.

From contributor C:
Contributor J brings up a valid point. Careful attention to detail in cleaning the insert seats, proper torque on the screws and indexing are essential. Even then, there may be small lines due to the geometry of the knives in the helical arrangement. In reality, the finish will be better than a spiral setup, but not equivalent to a straight knife cutterhead, no matter what anyone tells you!

On the other hand, contributor M testifies to the plus side of helical heads. Reduced noise is another distinct advantage!

One thing I have run into over the past few years having a bigger impact on these type of heads leaving lines or raised areas: using cheap import grade inserts. I have found that spending a little extra on Western European manufactured inserts makes a big difference in the end resulting cut. The European inserts have higher tolerances in thickness, hole location and carbide material itself. It would be like buying a brand new Mercedes, then turning around and putting the cheapest tires you could find on it, then wondering why you're not getting the handling performance you'd expect.

From the original questioner:
Decided to stick with straight knives for now. The biggest problem with straight knives is not setting them - after 25+ years in the business I can set them in record time - but getting them back from the sharpening service with usable tolerances. Don't mind honing them to get the burr edge off, but honing them to bring them into tolerance takes too long and is impossible for the longer blades. There's only one decent sharpener in NM and they're not that great. We have a set of Dispoz-a-blades in one of the small jointers and I'm quite impressed with them - they last longer than the Terminus and their tolerance across the length of the blade is very tight, + or - .002. The helical head we were considering was the Byrd and we might convert one of the planers over to that since we don't glue off a planed surface.

From contributor J:
I just wanted to clarify what I was talking about with the sharpening "on the head." My experience was with the Sidewinder brand helical. It doesn't use the 4 sided teeth like the Shelix. But experienced the same results that I imagine all insert type heads produce, i.e. lines. Those can be re-sharpened a time or two, but I don't know if they make a model fit for a planer or jointer.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
We use 3 Terminus heads in our molder as well as the insert small knife heads. We use rounded edge inserts and check on a comparator to see if there is a high knife then adjust. These are wonderful heads and do the job.

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