Cutterhead Options for a Five-Head Moulder

Shop owners who machine S4S mouldings discuss the relative merits of carbide versus high-speed steel knives, and 2-sided versus insert cutter heads. September 15, 2006

We run a ton of S4S material on our 5 head moulder. I want to go to carbide blades/heads. Benefits are twofold. First, I will get more miles with carbide. Second, I will have an easier setup with uniform heads/blades. I understand there are two ways to go:
1. Spiral heads with insert, small, 4-sided carbide blades.
2. Heads with straight, 2-sided carbide blades.
What are the pros and cons with each of these?

Forum Responses
(Solid Wood Machining Forum)
From contributor J:
That would depend what you're milling and how it's going to be finished (if at all). You would have to be more detailed. The 4-sided small carbide insert type spiral head, when you get it from the factory, will be great. When you turn them all to get a fresh sharp, you will get lines and small grooves. The straight blades? Make sure the heads have the same degree pocket you have now, because (at least in hardwood) you might get a lot of chip out.

From contributor R:
Spiral is the least expensive way to go. The product will most likely have to be sanded due to slight variations in blend from knife to knife. Get a chip in blade, turn it or replace it. Very cost effective - replace only the knives in the area of head used. 2-sided carbide blades are great for wood that you don't want to sand. No blend area lines. Get a chip in one blade, you will have to offset to cover; get a chip in both, replace or flip to new blade. This is the most costly way.

From contributor S:
Three ways to go, maybe more. The third way would use an inlaid carbide edge in corrugated knife stock. The advantage to this approach is the possibility of in-house re-sharpening, and lots of it, since this kind of knife stock usually has 10 mm or so of usable carbide.

The reversible inserts are okay, but when I used them, I was never confident that they were the most economical.

The four-sided insert heads cut with a lower decibel level (quieter), but a lot of folks complain about the small lines that result from slightly differing cutting circles. If your S4S is going to see subsequent machining or sanding, the lines might not be a concern. I'm not sure carbide knives/heads can or should be touted as being any easier (or more difficult) to set up in a moulder, but for sure you can get more miles from them than HSS in most any lumber. All you have to do is be willing to live with the initial disappointing finish that carbide, even when freshly sharpened, gives you. Just my opinion.

From contributor J:
What about the 3-4 wing single blade spiral? The blade bends into the wing? I think I have read something about that sort of thing. Or even a fixed curved blade? 3 or 4 of them per head? I can't think of the name.

From the original questioner:
Well, I got a spiral head to try out. It has 15mm x 15mm x 2.5mm blades. I am now running s4s fairly fast (60fm) and the surface looks really good. It will still have to be lightly sanded, but I think it will work. Might be a different story as the blades wear. Also, the head is hollow, not a solid head like I've seen before. It does weigh a lot less. You can see the ends of the screws from the inside. Anyone use the hollow heads?

From contributor P:
I have one of the hollow type insert heads. I needed one fast, and Grizzly had one. I bought it against my better judgment, but it worked. I had a zillion curved drawer faces to do on a shaper. Over time, the cut quality got worse. It seems to want to bulge when you tighten the nut. Or at least that is what my dial indicator is showing. This distortion seems to be affecting the way the inserts repeat. I don't use it anymore and will probably go with a Terminus head next time.

From contributor T:
We have Tersa heads on a 20 inch jointer and a 24 inch planer. We have a Terminus head on a Sintex 4 side planer. Both of these heads are self-aligning, but the Tersa heads are much easier to load. (You can do this with the head on the spindle.) Once loaded, the Terminus heads outlast the Tersa heads by a substantial amount. I would pick the Terminus heads for all machines if I could do it over.

From contributor B:
I run a lot of s-4-s as well as profiled mouldings, like the 4 sided inserts with the slight radius on the corners. I use the square inserts for my first bottom cutter, as they are used to joint the material. I leave about .031" heavy for my wide belt guy to hit both sides. My top cutter uses the square type, because most of my profile work comes out of the moulder face down. I like 4 sides, 4 turns if necessary.

From contributor E:
I like Terminus as well and I have a sales rep coming by on Friday to help with modification of a dedicated cutter that has caused headaches for 6 years. Terminus has increased their product variations to where you can s-4-s , rebate, bevel, etc. on the same cutterhead. They don't just sell products, they sell profits.

From contributor Y:
I've been using 4 sided carbide inserts in all the heads in my molder for all my S4S for over a year, and I've only had to rotate 3 chipped edges 90 degrees. At this rate, I might retire before I replace them all.

From contributor M:
Naptools offers the Sidewinder insert head. These heads use replaceable inserts in a true helical design. The heads are great for running S4S product. The heads offer increased life while reducing the noise level. If you have the capability to profile sharpen your own heads, the Sidewinder is a great option. If you can not profile sharpen your heads, then Naptools offers a sharpening service. The second option would be to use the turnable inserts. Naptools also offers these heads using the 15x15x2.5 inserts.

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

Comment from contributor K:
Carolina Specialty Tools makes 4 and 6 wing spiral heads. The 4 wing are used for hogging or first bottom head applications and the 6 wing are used for finishing applications. They use 15 x 15 x 2.5 four sided radius inserts. The 4 wing heads will tend to leave lines, whereas the 6 wing heads leave no lines. What you generally see from the 6 wing heads are pressure marks in the wood.