Bowl gouge flute depths

[Jon Murphy]

There are many terms for bowl gouges, deep flute, U shape, V shape, etc. I understand the difference between the U and the V, even though the V doesn't look like a V. The U has relatively vertical internal sides then a transition to the base - the V is more a sort of "double parabola" V, a smooth transition along the entire flute curve.

I am a fan of the Ellsworth grind and have a pair (1/2 and 3/8 - 5/8 and 1/2 US measurement) of Crown Signatures - the Ellsworth is a "deep flute" V, but deep flute has a number of meanings. I'm getting low on flute length and will soon need new ones. I like getting unhandled tools (Alan Lacer says that for a wood turner to buy a handled tool is like sending corn to Iowa - a variation on the old "coals to Newcastle" - I agree). The problem is the depth of the flute. My Crown Ellsworth Signatures have a depth of 62.5% of the stock diameter (i.e, the remaining "base" is 37.5%). I experimented with a Benjamin's Best 5/8 V bowl gouge that I use as a test tool, I didn't get the Ellsworth shape I wanted. The BB has a flute depth of 57.5%. Doug Thompson's U shaped bowl gouge has a depth of 54% (I have one that I use for a "bottom gouge" with an 85 dg. tip bevel), and he tells me that his Vs are the same depth (but he has a deeper one that he tells me he will measure when he gets home from a road trip).

I think the flute depth is an important part of the shape of the Ellsworth grind, my test on the Benji's Best seems to confirm that even though the difference is small (62.5% vs. 57.5%). The parabolic curve on the wings is flatter the less the depth of the flute, and that changes the amount of edge presented to the wood in the various angles of attack. I would appreciate opinions from other experimenters, I don't have the money to try various vendors. I think David's grind depends on having a really deep flute. My guess is that it should be at least 60% of stock diameter. Less than that and the "wing parabola" will be too flat. Unless one of you contradicts my assumptions on the need for flute depth for an effective Ellsworth grind I'll have to replace my current ones (when they run out of steel) with fully price handled vendor Signatures, unless I can find unhandled ones with the depth.

While I'm here let me offer a hint, a way to "eyeball" the depth of a flute without breaking out the calipers. Hold the gouge under a direct light with the flutes vertical so the reflection off the shaft is lined up with the middle of the shaft. If the top of the tip bevel is in line with the reflection then the flute depth is 50%. You can compare spindle/detail gouge shapes, or bowl gouge shapes, this way.

[Bill Blasic]

Look at the Thompson 5/8 deep flute bowl gouge, I think it might just be what you are looking for.

[Joe Bradshaw]

For me personally, it does not matter. I found edge bevel that I liked, and have sharpened all my bowl gouges to that bevel angle. I have Thompsons, Sorbys, Crown and some strays. Just keep your cutting edge sharp, and everything else will fall into place. Good luck.
Joe

[Lloyd Butler]

Joe,

I think you will find that the sides of the flutes in V and U are straight, so the distance from the inner surface to the outer part of the tool varies quite a bit up and down the flute. On the Super Flutes, Deep flutes or parabolic flute the walls of the flute have a slight curve to them, so the distance from the inside to the outside of the tool is closer to the same. I do not think it will be the exact same, but much closer than the U and V's.

So when you put a side grind on, the wings will have slightly different shape on them. I do not think it is the depth the flute your are looking for, but the flute shape.

For me, the wings have not been a big issue, I am more concerned when I first grab the tool of the bottom of the flute shape. I find the V (BB style) has a variable cutting width as you rotate the tool, so you can close down the cut and take a smaller bite, great for finishing. On the U that nose has a broader cutting arch and it is great for roughing green wood as it takes a slightly bigger bite. I do not have any parabolic flutes.

[Roger Chandler]

One thing to keep in mind is that the amount of steel left underneath a flute effects the harmonics [vibration] of the cut, and will increase all the more the further the tool is hanging off the tool rest. I have a deep flute 5/8" gouge and a 1/2" as well, from one manufacturer, and then the same sizes from Thompson.

I can hang the Thompson off the rest a little farther than the other one, although they are the same diameter tools. If I understand correctly, the parabola is an oval shape of the flute for the most part, and that also affects the grind result you get, which a lot of turners actually prefer.

[Thom Sturgill]

I wish to disagree with a point - the Crown Ellsworth gouges are NOT a 'V' flute they are parabolic. Doug's 'V' flutes have a flat side. He does make a parabolic - for Lyle Jameison - but does not list it on his site. Dave Schweitzer (sp) from D-Way produces a parabolic flute.

Lloyd makes a good point on the difference. Roger is also correct that Doug intentionally keeps more metal under the flute to suppress vibration. He also makes a sharper 'V' - especially on the Jimmy Clewes signature gouges - than other manufacturers for the same reason.

Doug Thompson claimed in a sharpening video, that the same edge geometry can be created by grinding the straight sided flute to a rounded profile instead of the straight profile that Ellsworth uses. I think this issue is more important than the actual depth of the flute.

[Reed Gray]

I guess the most difficult thing for me to figure out is why one gouge will work on one piece of wood, but not on the next. Then I get a different flute shape for that piece and it works better. I have the Thompson V and U flutes, a Jamieson parabolic flute, a few of the Oneway parabolic flutes, an Ellsworth, and some standard half circle flutes, and not one of them works in every situation. Of course, it can't be the fault of the driver, it has to be a plot by the manufacturers......

robo hippy

[Marc Tuunanen]

I agree Reed it's a plot... Cats and Dogs living together, Oh my....

[Bob Bergstrom]

Here's another observation test. I have three 3/8" spindle gouges, a Pinnicle, Thompson and a D-Way. I scratched the top edge of the flute one gouge against the top edge of the flute of the other. Kind of like a peeling cut. The Pinnicle and D-Way will scratch the Thompson, but the Thompson won't scratch the other two. Not an official test, but I would think the harder steel will scratch the softer one. The D-Way will scratch both, but the Pinnicle won't scratch the D-Way.

[Shawn Pachlhofer]

back to the OP's question...

The Crown Pro-PM Ellsworth gouge is the same as the Crown Pro-PM bowl gouge...with the Ellsworth version you're paying more to have David's "grind" on it when you buy it. You can save yourself a few bucks and grind the non-Ellsworth version into his grind. You'll mostly be taking away metal from the top of the tool, not the bottom of the flute, so you're not really losing much of the tool if you do that.

The closest flute geometry to the Crown Pro-PM Ellsworth is the Artisan Superflute from CSUSA. This is straight from David himself (and I would guess David would not recommend Lyle Jamieson's gouge, read below). I have both tools, both ground the same (so use one till it's dull, then switch tools - then back to the grinder with 2 tools). I can tell a slight difference between the Crown and the Apprentice. The crown does hold an edge longer.

I also also have a regular Crown Pro-PM bowl gouge, and it has the exact same flute as the Ellsworth version.

As Thom mentioned - Doug Thompson does make a parabolic flute for Lyle Jamieson, and it is only available direct from Lyle. That flute is very similar to the Crown - but I've never compared them side-by-side to know for sure.

I've also never looked at the D-way to know what it looks like.

So here's my gripe (vendors are you listening?) - a side or 3/4 view of the end of tool is worthless is a buyer is concerned about flute shape or how much meat is in the bottom of the gouge. Offer us an "end view" so we can really see what we're getting.

If you want to buy an unhandled gouge - I would look at the Jamieson/Thompson or the D-way

[Jon Murphy]

A belated thanks to you all, and my apologies for not coming back sooner. Some medical matters got me away from bowl turning for a while - although I was able to stay with small spindle turnings.

As I'm now back on bowls, I finally got to do a bit of comparison shopping using the above advice. May I specifically thank Shawn for pointing out that the "standard" Crown Pro-PM has the same flute shape as their Ellsworth version. The Pro-PM "standard" 5/8" comes in at $96.50 from Craft Supplies (Woodturner's Catalog), about $12 more than the Artisan. The Jamieson/Thompson and D-way unhandled are a bit more, or a slight saving (my memory of my search is fading <g>).

Which brings me to my gripe on vendors! Why do they charge premium prices for special factory grinds when we all end up with something a bit different as we sharpen our tools (don't answer, I know the answer).

I will now go into a Murph Says (my domain name, and my habit). Sometimes one has to spend money to save money. About three years ago, having been a wood turner since 1997, I invested in a beveled edge CBN wheel from D-way. I make my own Ellsworth style hollowing tool bits from stock (I get three or four bits out of a $3.80 10% carbide blank) and needed the beveled edge. I needed a new "fine" wheel and decided to give the CBN a try as I was tired of not only flattening but also beveling my shrinking AO wheels. I already had the Oneway jig and the Geiger "Vertical Solution" grinder arm and was able to make almost any grind shape (tip vs. wings). BTW, I've told David he should advertise that ability, but he sticks with the specific settings. It takes a couple of hours to work out the "angles of the dangles" using an old tool, but once worked out and written down they are there. Within a year I'd blown another $200 (I think a bit less) on D-way's coarse CBN wheel.

Time is money, and so is steel. As the CBN wheel doesn't wear down the angles don't change, a touch-up is one or two light passes. As the CBN is a cool grind one can reshape a tool quickly and without a break for cooling HSS, or dousing carbon steel in water. Temper is not lost. I would never recommend the CBN wheels to a new turner as many of them give up quickly, but to a committed turner it is a God send. I buy cheap tools, particularly scrapers and such, from PSI. They are a good firm, my lathe is a PSI Commander 12" (and they are an hour's drive from me, and good people), but their tools are made in China to their specs and of decent steel. The handles are lousy, so I rehandle them. I can regrind the shape of my scrapers to fit the job in a few minutes, and not worry about the lost metal as I can get a new one for under 20 bucks.

This does not apply to my beloved skew chisels, they are unhandled Alan Lacer's, or my detail gouges and bowl gouges - except for some that I'm always changing. "Ye shall know the craftsman by his tools", but some of the tools are for one time use and are reshaped for other uses. Like all of us (or most), I started out by buying Sorby or other advertised tools - and spent more than they were worth for their basic steel and handle. I learned relatively early that specialty tools were a waste of money, and that learning the skills was better. I've given away such things as my skewchigouge (Crown) and the Sorby thingamebob (name forgotten) that was supposed to be fool proof.

Again, my thanks for your responses. I fully agree with the general consensus that the shape of the flutes is more a matter of what one is comfortable with than the actual shape. I am used to my Ellsworth signature for my bowl gouges and wanted to duplicate that. BTW, Doug will sell you an unground version of any of his gouges - I don't remember if he discounted it but it didn't matter. I made an 85 dg. "bottoming" gouge to my taste from a Thompson "U" blank. I have replaced my standard spindle gouges with Doug's "detail" gouges (the difference being flute depth), and have reground the old spindle gouges for special use.