Stewart Batty 40/40 grind with Wolverine jig

The advantage?

Ellis Walentine

Thanks for the specifics on how to create Stuart's grind, but, in the words of the old editor, why should I want this grind?

Ellis

Re: The advantage?

john lucas

Well that's a good question that I am still working on. The big advantage is the 40 degree bevel angle. It cuts a lot cleaner than the normal 55 degree that most people grind with the standard Ellsworth or Irish grind. The wings are also 40 degree so when the nose starts to get dull you simply rotate the tool slightly and have a fresh clean edge that cuts the same as the nose so you don't have to change your turning angle to get a fresh edge. This is a good cutting angle for bowls that are more open and have a good continuous cut from lip to bottom. Stewart uses mostly the push cut. There is a cut where you have the flute almost straight up at about 12 oclock. The cut is on the wing and the wood is coming across this vertical edge very shear so it leaves a very clean cut. In this case it's both the 40 degree grind and the shear angle that leaves the clean cut. This cut also applies very little pressure with the bevel against the wood.

I grew up using the Ellsworth grind or what ever we are going to call it. Learned it from John Jordan. The more blunt 55 degree grind lets you do steeper sided bowls without losing the bevel. The wings depending on whose system you use to grind it and the shape of the flute change the included angle of the wings. On my U shaped gouge I have ground the wings quite sharp. About 30 degrees. Doesn't hold an edge long but on a pull cut will give a very clean cut. My normal gouge is the Thompson V shaped and I grind it so the wings are closer to 40 degree give or take a little. Still cuts clean on a pull cut but can be used to really hog away wood when roughing.

I still use the Irish or Ellsworth grind for most of my work mostly because that's what I'm used to. I'm reaching for the 40/40 grind more and more especially for final passes where a really sharp fresh edge pays off in reduced sanding and less tearout.

Others may have more to say about this. I noticed that Mike Mahoney is now using very small bevels and a 40 degree grind on the nose. I haven't held one of his tools so can't comment on the other angles.

Re: Stewart Batty 40/40 grind with Wolverine jig

Josh bowman

Although I don't use the 40 40 40 anymore, what got me to use it was, there is no real need for a jig. Just put the flat platform to 40 and measure and draw a line from the platform center to.....I think 40 on both sides of the1200 position . Put the gouge on one of the lines rolled over at about 40, start grinding while rolling and swinging the gouge until the nose is at 1200. Then repeat on the other wing. This is easier done than said. I would think this would be a perfect grind for someone doing demo's, since all you need is a basic grinder to get by.

Re: Stewart Batty 40/40 grind with Wolverine jig *LINK*

Josh Bowman

Here's the Ashley Harwood example of the 40-40 grind. This is a little off topic to what John is doing, but I'm answering the question from Ellis.


http://www.carolinamountainwoodturners.org/articles/480

Angle of the Side Grind - Measure?

Jake Niedling

John,

What is the reference for measuring the side grind? The nose is pretty simple using the bottom of the flute. On the side where you have different flute shapes, I am never quite sure how to measure this.

I primarily use the basic Fingernail grind (Elsworth/Irish grind) with a nose ange of about 62 degrees and I don't even know what the side angle is on it. I am so comfortable with this grind, that I use it 80% of the time whether I am turning bowls or spindles. I find that with a fresh edge on my last couple of passes produces a pretty clean cut. Everytime I try someone elses grind, I never get as comfortable with it as I do with my fingernail grind. So I always go back to what works for me.

Jake

Re: Angle of the Side Grind - Measure?

john lucas

Jake I only measured the side wings because people always ask me. I have a special tool to get close. It only has V shaped grooves every 5 degrees so it's not dead on just lets me get some idea of what the wings are. Of course if you use the Michelson grind the wings are kind of a radius so I can't really measure those.

Re: Stewart Batty 40/40 grind with Wolverine jig

robo hippy

I tried it and found it to be a better detail type gouge than a bowl gouge. It is just too pointy for me. I found 45/45 more suited to bowl work. I only like the 60 or so degree bevels for the transition and going across the bottom. Need to get my platform grinding video complete...

robo hippy

I use my roborest for the 40/40

john lucas

I scribed lines at 45 degrees to help me judge where to start the gouge. I start from one of the lines with the flute pointed in and roll toward the middle rotating the gouge until the flute points up. Very fast and easy to learn.

Stewart says that any grind more acute than 40 degrees and the tool wants to self feed. More blunt and you have more pressure on the bevel. I can't seem to tell. I have spindle gouges sharpened to 35 degrees and don't think they self feed. I have ground my gouge to 45/45 and can't tell the difference between that and 40/40. I think I have a pretty sensitive touch but I haven't turned as much as Stewart so perhaps have more to learn.

photo showing different grinds

john lucas

Top to bottom the way I understand the names of the grinds. Traditional grind, Stewart Batty 40/40 grind/ Ellsworth or Irish grind or other swept back wings. I'm really not sure what exactly is the diffference in the Irish Grind vs the Ellsworth grind. I know the grind I use straight off the Wolverine is very slightly different than the Ellsworth and a lot of the shape depends on the flute shape. The Ellsworth flute is slightly different than some of the others.

I have ground the traditional grind on a homemade U shaped gouge. My 40/40 grind is on a Henry Taylor U shaped gouge and the bottom tool is a Thompson V shaped gouge.

There are many more variations of the Irish grind. I have one with very long wings that I used years ago.

Re: photo showing different grinds

Robert Lalonde

After watching Stuart and Ashley demo his 40/40 at AAW and the Oregon and desert symposiums, I decided to give it a try, Sorry, but I just don't care for it. To aggressive for my taste. I use 55 degrees with swept back wings most of the time. I also have a gouge ground at 45 degrees with even longer wings when I want very clean surface or want to get into a tight corner.

Lately, I've been using a Rudy Lopez style negative rake scraper ground to a cumulative angle of 50 degrees for a final pass. Seems to work pretty good but I'm withholding judgement for now.

Re: photo showing different grinds

john lucas

That gouge does have a learning curve if you are used to the older Irish grind. It works better when you don't force the tool. Just let it cut at the rate it wants to cut at. It's very controllable when you do that and leaves a very clean finish.

Stewart Batty had an excellent article on negative rake scrapers in American Woodturner a few years back. I know I started playing with one after seeing his demo and I'll bet Rudy did the same thing.