HELICAL VS: SPIRAL CUTTER HEAD

[frankc4113]

I'm going to be buying a 15" planer, probably Grizzly. There are 2 models, one with a spiral cutter head and one with a helical cutter head.
I'm looking to see what the difference in cut quality is, if any, between the two. Does either spiral or helical stand out as giving a smoother cut with less finish sanding or would it be a better idea to buy a cheaper 15" model (about half the price) with straight knives and then change the cutter to Byrd Shelix or comparable cutter?

 

[bob vaughan]

"Spiral" is a term often mis-applied.
A helix is a ramp wrapped around a cylinder. A constant radius.
A spiral is a ramp wrapped around a cone. A decreasing radius.
When did we last hear someone correctly referring to a helical staircase?
Its one of those technical geometry terms that common use momentum causes confusion.

As to smoothest cut, I can't attest. I prefer straight knives on both a jointer and a planer.

A lot of people call this a smooth cut and are satisfied with it.

 

[Mike Davis]

I have seen a couple sold as helical that produced a surface like that, one was much worse. I spent most of a day working on it and could not get it any better. They had the cutters set parallel to the shaft. The ones I saw only had one cutter at any one point on the shaft. Single helix.

The Byrd Shelix brand is much better but still has fine cups. I think they use a double helix. The cutters are set on an angle following the helix so that each cutter is angled as you would use a hand plane. The cutters overlap more so the pattern is smaller and not so deep. I’d guess less than a half that deep. You still have to sand or scrap to get a perfectly flat surface. Most production shops have a wide sander so the lower frequency of chip out and quieter running of the Byrd is an advantage to them. Home shops without a wide sander use a hand held random orbital sander to finish the boards.

If you are set on buying one the Byrd is definitely worth the difference in cost. You will never be satisfied with anything less.

 

[chris_goris]

The difference is in the inserts. I think the first to hit the woodworking scene was the "spriral head" but I not certain and for this exercise it doesnt matter. Both are insert type heads with replaceable cutters. The main difference is the spiral head is like a mini straight knife cutter wrapped around the cutter cylinder in a helical fashion. My Powermatic jointer has them and they are about an inch long or so . These cutters are only indexable 180 degrees , where as the "helical head" uses machine tool type inserts. The machine tool type insert has 4 cutting faces that can be individually indexed 90 degrees as they wear or chip. I honestly dont know which one is "better". But it seems to me the spiral head is a little safer since it uses standard gibs like a stright knife machine to hold the inserts in place. I have heard stories of screws coming loose on helical heads and becoming projectiles.

 

[MarkE]

I used to have a Grizzly G0453Z 15" planer with a Spiral cutterhead.
A couple of years ago I upgraded to the Grizzly G1033X 20" planer with Helical cutterhead.

I have seen no difference in cut quality from one machine to the other.
Both planers use 4 sided carbide inserts.
The G0453 uses 14mm x 14mm
The G1033X (V2) uses 15mm x 15mm

 

[BKHam]

helical cutters are not at 90 degrees to the push direction, rather they are skewed and thus enjoy the same benefits as hand planing with a skewed action. spiral uses the same replaceable cutters but they are 90 degrees to the push direction and act as very small straight knives. they are easier to replace and index than full size straight knives but would undoubtedly not have the cut quality of the true helical.

 

[bob vaughan]

I think that the scale of the cutterhead is a factor to consider. Larger cutter heads will have five or six rows of cutters. Smaller diameter cutter heads don't have room for that.
Below are some photos I have, first is a straight knife cut example of a little Delta suitcase screamer that was having trouble. It just needed knives. The others are examples I've run across.

For me, I'll stick with straight knife heads. They take less power so I can remove more stock with the same motor at least when the knives are sharp. It takes me about an hour to change knives in my 18" planer assuming no other adjustments are required. I'll first set my gauge to the height of the existing knives then set the new knives to that same dimension. This requires two sets of knives.

Popular myth seems to imply that changing straight knives is a taunting process requiring a great deal of skill. I don't think so. Yes, the first time is stressful if you've got no one around to show the process. The first time I did my knives on my Sears box-bed 6" jointer was scary and tedious. The next time it was routine. There's a video out there on making your own gauge bases for planer setting using a $30.00 (or less) dial indicator.

streaking resulting from dull knives. hard maple.

After sharpened knives were installed. Much better.

The planer used for the above straight knife sample cuts.

Powermatic 20 or 24" planer head.

Unknown Taiwan-made planer head. Five or six rows of cutters.

Unknown brand of Taiwan-made jointer head.

 

[Mike Davis]

I'm staying with straight knives for much the same reasons. I can take the knives out one at a time, sharpen on my diamond stones, reset to match existing, then do the next one. I usually write the date sharpened either on the back of the blade on a piece of tape inside the cover. Not that I keep up with it all that much, just as a reminder how long it's been. If I used it regularly, even once a week I would keep up with it better. Anyway, yeah, about an hour to take it all apart, sharpen and reinstall each blade, then all back together. The tool steel blades last me a very long time. About $50 a set for my 12 inch DeWalt.

 

[blackhawk]

I have the Grizzly G0490X with the spiral cutterhead. I am running something through it on almost a daily basis. The cut and finish is incredible. I have owned it for almost 5 years and still haven't turned the inserts. I had an older Grizzly straight knife jointer before this. I would never go back to straight knives. I have an 18" planer with straight knives now, only thing stopping me from buying a spiral head for it is the cost. It is a much better deal if you buy the machine with the spiral head from the factory.

 

[drw]

Straight knives vs. helical cutters...I have both (planner has knives, jointer has helical cutters) and I have had positive experiences with both. That said, if given the choice I would go with the helical cutters (smooth cuts, less noise, carbide edges stay sharp for a very long time). On the issue of power, I am not sure I understand Bob's comment that straight knives require less power; intuitively, I have assumed the opposite to be true. At any one point in time, the helical cutters have a very small surface in contact with the wood. On the other hand, while the knives are not in constant contact with the wood, when it is in contact it is along a much longer surface. Please note, I am not arguing the point (I really don't know), simply making an observational point.

 

[chris_goris]

helical cutters are not at 90 degrees to the push direction, rather they are skewed and thus enjoy the same benefits as hand planing with a skewed action. spiral uses the same replaceable cutters but they are 90 degrees to the push direction and act as very small straight knives. they are easier to replace and index than full size straight knives but would undoubtedly not have the cut quality of the true helical.

not sure what youre referring to here, maybe you can clarify?

 

[junquecol]

would it be a better idea to buy a cheaper 15" model (about half the price) with straight knives and then change the cutter to Byrd Shelix or comparable cutter?

This would be my choice as the cost is about the same, but get get a genuine Byrd head.

 

[chris_goris]

I used to have a Grizzly G0453Z 15" planer with a Spiral cutterhead.
A couple of years ago I upgraded to the Grizzly G1033X 20" planer with Helical cutterhead.

I have seen no difference in cut quality from one machine to the other.
Both planers use 4 sided carbide inserts.
The G0453 uses 14mm x 14mm
The G1033X (V2) uses 15mm x 15mm

It appears Grizzly is calling "helical" the same as "spiral", again, 2 different animals.

 

[BKHam]

not sure what youre referring to here, maybe you can clarify?

the brown represents the wood and the feed direction in blue.

the cutterheads look very similar with staggered replaceable cutters but on the helical they are angled to the feed direction and on the spiral they are not. the skewed or angled cut will give you a smoother surface much like skewing a hand plane.

 

[creasman]

the cutterheads look very similar with staggered replaceable cutters but on the helical they are angled to the feed direction and on the spiral they are not. the skewed or angled cut will give you a smoother surface much like skewing a hand plane.

I definitely see the advantage of the angled cutters. I often skew a hand plane to get a smoother cut. For those that own the Byrd cutter replacement head are these angled or straight?

 

[BKHam]

I definitely see the advantage of the angled cutters. I often skew a hand plane to get a smoother cut. For those that own the Byrd cutter replacement head are these angled or straight?

my byrd replacement for the Dewalt planer and my powermatic 8 inch jointer are both helical / angled.

 

[chris_goris]

the brown represents the wood and the feed direction in blue.

the cutterheads look very similar with staggered replaceable cutters but on the helical they are angled to the feed direction and on the spiral they are not. the skewed or angled cut will give you a smoother surface much like skewing a hand plane.

View attachment 192240

Have a look at the head on my Spiral cutterhead on my jointer in my original posting here, the cutters are not straight (normal) to the centerline of the machine. The term spiral is a misnomer for this application, both are technically helical but different types of cutters.

 

[BKHam]

Have a look at the head on my Spiral cutterhead on my jointer in my original posting here, the cutters are not straight (normal) to the centerline of the machine. The term spiral is a misnomer for this application, both are technically helical but different types of cutters.

there is picture labeled powermatic...hard to see on that one. the pic with just a cutterhead not in a machine is helical.

there are undoubtedly some misrepresentations / bad labeling from some manufacturers.

Grizzly....the manufacturer mentioned at start of the post classifies cutterheads in the way i described.

 

[gmakra]

This is a helical head and its made by Newman Whitney in NC and is huge money.
A Byrd is a spiral head.
This should end the debate.

 

[BKHam]

View attachment 192241

This is a helical head and its made by Newman Whitney in NC and is huge money.
A Byrd is a spiral head.
This should end the debate.
[/QUOTE

maybe we like debating