Vector Drives and Parabolic flutes -Seriously!

[Roger Chandler]

I had a call from a woodturning friend, [Scott Trumbo-Serious Tool Works] yesterday, and he wanted to touch base about family, etc, and asked if I was going to be able to make it to the AAW Symposium in Atlanta? Unfortunately, circumstances with my schedule and such won't allow that this year [] as I would certainly liked to have been able to take the symposium in for sure! There is a great lineup of demonstrators, and the instant gallery is sure to be a world class display of things off the lathe.

He then asked about the Virginia Symposium, which will be held first week of November. My plans are to make that for sure. He mentioned there is a turner near me, who is going to get the newest version of the Serious SL2542 at the AAW symposium, and will be using it to demo at the Virginia Symposium in November. I will be able to get an up close look at this latest version for sure.

Scott mentioned they have an updated Vector drive on it, which he describes this way...... "This latest version features vector drive, which functions similar to cruise control on a car,--provides amazing torque delivery."

He also mentioned that the turner is going to become an east coast representative for Serious Tool Works. Serious Tool Works is also going through the process of retooling their gouge line, and will begin in September to offer their Ultimate Gouge and M2 gouges with a parabolic flute instead of the V flutes they currently use. He mentioned that they have gotten many requests from turners to offer the parabolic flute configuration. I think I am going to try one of those when they get in stock!

I am a bit of a tool-a-holic, at least that is what my wife thinks. and those who have been in my shop can attest to that, but I am one who likes to keep abreast of what is being offered and is new in the woodworking world. I am also one who likes to share information on these forums, like most of us do......it helps us to know what others experiences are, so when I get the chance to get a bit of time with the SL2542 at the VA. symposium, and get a chance to put one of those new Ultimate parabolics through its paces, I will share my impressions.

I have been wanting to take a spin on one of those Serious Lathes for some time now......maybe this opportunity will give me a better and broader perspective on what to do when it comes time for me to get my final "dream lathe."

I share this, not as a promotional thing, but as informational to the "creeker" family, and invite discussion on parabolic vs. "V" flute configurations, and their advantages/disadvantages. and also other things related to types of drives/inverters, etc.
Your $0.02?

[John K Jordan]

At the TAW Symposium demonstrator Glenn Lucas (IFRC) was a proponent of the parabolic flutes saying it was easier to put sharpen a smooth profile on them. I haven't tried one and have no reason to doubt him, although I can't remember having any problem with my bowl gouges. I'm not where I can get to my notes right now but I'll check them when I get back.

[Roger Chandler]

At the TAW Symposium demonstrator Glenn Lucas (IFRC) was a proponent of the parabolic flutes saying it was easier to put sharpen a smooth profile on them. I haven't tried one and have no reason to doubt him, although I can't remember having any problem with my bowl gouges. I'm not where I can get to my notes right now but I'll check them when I get back.

If I understand correctly, John, I think one of the benefits of a paraboloc flute is the evacuation of chips from the cut, as there is more room in the flute than in a V configuration.

[Jason Edwards]

If Serious is adding a vector drive, they are playing catch-up. Robust has been doing it for years, and I believe Oneway, Vicmarc and even Powermatic have been using vector drives for quite sometime.

[Roger Chandler]

If Serious is adding a vector drive, they are playing catch-up. Robust has been doing it for years, and I believe Oneway, Vicmarc and even Powermatic have been using vector drives for quite sometime.

Not sure on the when of things.....I do know he said that this was the latest updated version he is taking to Atlanta for the AAW Symposium.

I do know that the "M" series Delta Electronics Inverter on my G0766 is a sensorless Vector micro drive, so I would imagine that the Serious SL2542 has that technology as well, whether the inverter is from another manufacturer or Delta? They are especially made to cut out interference and noise, according to the information I just read on a vendor's website.

[Reed Gray]

I do know the vector drive had been around for a while, so nothing new there. I would need an engineer to explain it better, but I think it keeps torque levels higher when resistance/cutting force is applied.

I would like a good explanation of the parabolic flute advantages. I do have a couple of them, Lyle's, 2 Oneway, and an old Ellsworth. I asked Doug about them once and he commented that with a slightly curved wing, his V is the same thing. Some times the wood cuts better with a V, some times with a U, some times with the parabolic, some times just the half round flute. No idea why.

robo hippy

[Roger Chandler]

I do know the vector drive had been around for a while, so nothing new there. I would need an engineer to explain it better, but I think it keeps torque levels higher when resistance/cutting force is applied.

I would like a good explanation of the parabolic flute advantages. I do have a couple of them, Lyle's, 2 Oneway, and an old Ellsworth. I asked Doug about them once and he commented that with a slightly curved wing, his V is the same thing. Some times the wood cuts better with a V, some times with a U, some times with the parabolic, some times just the half round flute. No idea why.

robo hippy

Reed, it is my understanding as well, that the more resistance in the cut, the more torque the vector drive applies, as it senses the resistance.

As for the why's of the advantages on some woods with some flutes...........well, that may remain one of the great mysteries of the universe, perhaps never discovered by man!???

[Roger Chandler]

Here is some info on vector drive inverters.....seems there are "sensorless" and those with encoders that read shaft speed, etc.

Best Answer: Sensorless vector control is a variable frequency drive (VFD) control strategy that improves motor performance by regulating the VFD output based on a mathematical determination of motor characteristics and operating conditions. Operating conditions are estimated from measurements of electrical parameters. Sensorless vector control is called “sensorless” to distinguish it from vector control with encoder feedback which optimizes motor performance by regulating the VFD output based on motor shaft speed and position feedback from an encoder.

Both types of vector control provide improved performance over the basic control strategy called “V/Hz control” or “scalar control.” With the simplest type of V/Hz, control, the drive simply acts as a power supply that provides an adjustable output frequency with output voltage proportional to frequency. To provide the maximum possible motor torque with the minimum possible current, the motor voltage needs to be “fine tuned” to suit the exact motor characteristics and to compensate for changes in those characteristics due to load changes and motor temperature changes. To more closely regulate motor speed, the motor frequency needs to be “fine tuned” as well. Various vector control strategies are used to accomplish this.


If I understand this correctly, both sensorless and encoder can increase torque but one does it with fine tuning the motor/inverter for optimal performance and one does it by encoder with feedback to the inverter......for all you sparky's out there, is that pretty much the case? If so, it seems 6 of one, half dozen of the other?

I have this from Scott related to VFD drives......"
* There are only several companies producing small horsepower AC vector drives. Those drives can vary significantly in quality and cost. We use a premium Westinghouse vector drive."

[Dennis Ford]

"Vector drive" can maintain a more steady speed under varying load condition, the difference is almost negligible at "normal" speeds and more noticeable at very low frequency. I like parabolic flute bowl gouges but again the difference is pretty small.

[Thom Sturgill]

Parabolic (or more likely elliptical) flutes do offer a larger opening at the nose, but not so large as a U shaped gouge which IMHO makes them better in the transition.

As I understand, from a machining viewpoint, the parabolic bits that cut the flute are harder to make and re-sharpen than U or V shapes and thus more expensive. Elliptical is a good compromise and over the range of the flute almost indistinguishable.

From a turning point of view, since the side sweeps out in a curve, it is easier to get a good grind than a straight sided V gouge. Easier to be consistent since it can be straight in one plane and still give the control of a curved edge. I like my Thompsons, but my Ellsworth and D-way are my go-to gouges.

[Pat Scott]

I just got back from Glenn Lucas's 5-day Signature Class at Craft Supplies. This was my 3rd time taking his class (because I enjoy it so much).

I was told that contrary to popular belief, the gouge that Thompson makes for Lyle is NOT a parabolic flute, even though he calls it that. It's still a V gouge with the flute cut deeper. From what I was told/heard, I don't think Thompson knows what a parabolic flute is. If Thompson says: "that with a slightly curved wing, his V is the same thing..", then I know he doesn't know. The reason he and other manufacturers don't make a parabolic gouge is because it's cheaper to make a V or U. The cutters for a V or U can be bought off eBay! Putting a curve on the wing of a V gouge does not turn it into a parabolic. Rocking a V tool in an arc while sharpening does not make it a parabolic nor will it cut like a parabolic. Think about it - the sides of the flute are straight and come down to a sharp nose. How can you sharpen a straight edge into a parabolic? You can't. No matter what shape you put on the wings, it's still a straight flute. Put a straight edge against the flute on a Thompson gouge and it's flat.

For the type of cuts that Glenn makes on his bowls, you can not make the same cut with a V or U. The portion of the nose that does the cutting on a V is too small, on a U the part that does the cutting is too big. It's like the 3 Bears story - one is too hot, one too cold, and one just right. The parabolic is just right, the bevel/nose/flute is fluid and won't dig in like a V or U can.

Elliptical gouges are 1/8" taller than they are wide (I own 4 of Stuarts elliptical gouges). Stuart made a U gouge and an elliptical gouge. What's funny is that in his literature he never says what kind of flute the elliptical gouge has. It's not a "true" parabolic, it's his version that is a more what I call a relaxed V. D-Way is the same way (I own one of his gouges too), it's another relaxed V. It's not as steep or straight fluted as Thompsons, but the nose on an Elliptical and D-Way is not as gentle as a true parabolic.

Hamlet Masterflute (but not the Hamlet standard bowl gouge), Henry Taylor Superflute, Robert Sorby, all Oneway bowl gouges, and the Ellsworth Signature gouge made by Crown are all true parabolic flute gouges. You can read more about flutes on Peter Childs website (peterchild.co.uk/info1/sflute.htm).

Before all the hate mail comes, if you own a V or U or relaxed V, and it works for you and the type of turning that you do and you like it, that's what matters. If you think Thompson or some other brand out there is the best there is, that's what matters. I own all of the above types of gouges and use them all (mostly). But like you I have my favorite go-to gouges. Why does one gouge cut better than another? Why can I get a better curve or smoother finish from one gouge and not another? It might have something to do with the flute.

[Reed Gray]

Hmm, I do want to see Glenn some time, and maybe even take the class from him. Wonder if he would trade if I taught him how to use scrapers..... Interesting definition of 'parabolic' flutes that I have never heard. Makes a certain amount of sense. I do have 2 Oneway gouges that some times I really like, but no idea how they really work. I do prefer a more open nose since I cut with my tools held level.

robo hippy

[Bill Blasic]

Pat the only thing I will say on the subject is that Doug Thompson does know exactly what a parabolic flute is.

[hu lowery]

This thread manages to open not one but two cans of worms at once! The electronic drives range from very simple and not too smart, have to say my Delta, "M" series I believe, is in that category. At low RPM torque is down markedly although it might be better than with a less sophisticated current feed. The best of the electronic controls will feed more power to the motor as load increases keeping the RPM very close to stable. The better a controller does this, the more sophisticated and pricey they tend to be. Nobody can put a thousand dollar controller on a thousand dollar lathe and sell it for fifteen hundred after shipping, middle men, and profits, ain't gonna happen. The controllers used on lathes are one of the places that adjustments can be made to meet price points.

"Parabolic" is a fine buzz word that I have encountered in other areas also. Usually a term applied to something other than a true parabolic curve. It isn't hard to grind a tool to cut a parabolic flute these days, NC took care of that. Hand grinding consistently is basically impossible however and resharpening poises the same issues.

Parabolic flutes can be cut, we aren't going to encounter them too often unless someone either has an NC grinder or easy access to one however.

There is another thing at play when we talk about gouges however. It is quite possible to have a parabolic edge when the flute forms one curve and the grind another. While the flute might not be parabolic, and the grind might not be parabolic, the two combined together are.

Clear as mud, right?

Oh yeah, I'd make book that Doug Thompson knows about as much as there is to be known about flutes and grinds. The things that he hasn't done, he has at least explored the possibilities of doing.

I'm very unsure about a parabolic flute myself. It seems like it should be the best thing since bottled beer, on paper. Are end users going to be able to sharpen well enough to take advantage of the flute profile? If the edge is misground or missharpened it has the potential to be far worse than any conventional profile I believe.

Hu

[Kyle Iwamoto]

Thank you Pat! That was very informative. NO hate mail from me. I always wondered why my Crown 5/8" Ellsworth Pro PM is my favorite. I have several other brands as well, but that Ellsworth I really like. And I sharpen them all with the same jig and grind. Now I know why some gouges cut better than others, in different situations, and they all come from the same sharpening jig.