Been thinking 'bout physics

[Jon Prouty]

Been thinking about Grumbine's 45 45 45 bowl gouge positioning. Flute turned 45 degrees, 45 degrees to the ways and 45 degrees down. When roughing a bowl that is a bit out of round I get a lot of banging and thumping around of the gouge. It got me thinking about my easy wood tool. That EWT rougher is held flat. When the thumping gets too bad for the bowl gouge I get mad and grab my EWT rougher and get it round then back to the bowl gouge. I do most my roughing with a 5/8" V with Doug's 16" aluminum handle.

So, I been thinking 'bout them physics again and that 45 degree down is the killer to me I think. Every thump is pushing the gouge away from the wood rather than down into the tool rest. Why not bring it more parallel to the floor and let the tool rest take the brunt and the gouge not move away from the wood?

I am missing something here I imagine. Help enlighten me please.

Jon

[Steve Schlumpf]

Jon - when using the 45-45-45 method - you are presenting the blade of the gouge such that it slices the wood. The EWT is used as a scraper. Two different animals but they both get the job done. JMO.

[David E Keller]

I don't think you're missing anything, Jon. The 45/45/45 is just a suggested starting point, but there's no reason you can't vary any of the three axises to find a sweeter cut. Also, there's nothing wrong with that easy tool... I think whatever tool gets the job done is the right tool.

[terry mccammon]

I have feeling that Grumbine's grind on his gouge is such that this works for him and in fact pushes the tool down on the rest. Is there anyone who can say how he grinds his bowl gouge.

I do know this, since I have more or less no idea what I am up to, I am always fooling around with the profile on my tools. I can go from a pretty nice cut to a catch that tears a bowl out of the chuck with what appears to be a modest change in either tool orientation or tool profile.

As John Keeton has said "tool presentation" is the name of the game. I understand tool presentation to mean the combination of my hold on the gouge, the height of the rest relative to the center of the work piece, the 3 dimensional orientation of the gouge in space and the exact shape of the surface I am approaching. Given that any of the carbide scrapers out there, EZ Wood or home made, are about being on center, cutter more or less flat, the number of variables are reduced. Hence their appeal and success.

For me the challenge is figuring out how to make this all come together so that I get repeatable results. I suspect I am a long way away from achieving that goal.

Best.

Terry

[Dan Forman]

I tend to shift my gouge around a bit as David mentioned when bringing a blank to round.

Dan

[Faust M. Ruggiero]

Don't forget, Jon, that position came from The Big Guy's basic bowl turning video. It is a safe position meant to ride the bevel. Others teach a level tool position for roughing cuts ala David Ellsworth. They all work as long as you don't bite off too much for the wood or the lathe. A wood like green poplar may allow a 1/2" wide slice to be roughed away with the tool level to the rest and riding the bevel. However, that's may not be the best presentation for a new turner and that is the audience Bill Grumbine is addressing in that video.
faust

[Dan Hintz]

I have feeling that Grumbine's grind on his gouge is such that this works for him and in fact pushes the tool down on the rest. Is there anyone who can say how he grinds his bowl gouge.
There's nothing magical about the grind he uses... he sweeps the wings back quite a bit to prevent catches, but that's pretty much it.

[Reed Gray]

I prefer the scrapers for roughing bowls. I did one test spin on one of the carbide tipped scrapers, and they work fine, but are smaller than I prefer. The gouge method does work. If you want to hold it level you can, but you don't gently roll the tool over into the cut, you start with the flutes rolled all the way over. The difference here is with the handle lowered, you rub the bevel, and the tool stays balanced (part that is cutting is directly over the tool rest). With the handle level, if you roll it into the cut, the wing can catch. This is generally a pull cut.

robo hippy

[Ryan Baker]

Bill states in his video that his suggested 45-45-45 is just a ballpark presentation. You need to adjust from that point as necessary to get the right presentation angle for your particular grind, etc.

If an out-of-round blank is banging the tool like that, it is because the blank is smacking the bevel of the tool and pushing it away. Grumbine is describing how to set up a safe, controllable, bevel-rubbing cut. But that often isn't the presentation you want when roughing out a blank. A non-bevel-rubbing, more open presentation that directs the force into the rest works much better ... but you have to control the tool so that you don't take too big of a bite. It's something you just have to get a feel for. Start with the Grumbine cut, then lift the handle and rotate the flute up some, and you will see how the cut changes.

The easy rougher type tools do a good job of directing the force into the rest because they are taking a scraping cut -- that is probably their biggest advantage as far as ease of use. You can do exactly the same thing with any scraper. It's effective and there is nothing wrong with doing it that way. But the gouge will do it too, and it is worth the time experimenting with scrap to learn about different gouge presentation angles.

[Harry Robinette]

Your bouncing could be from riding the bevel to hard and creating more lumps instead of taking them out.

[Jamie Donaldson]

Big Bill primarily uses pull cuts, and his gouge profile is ground very much like the basic Ellsworth style side grind. I primarily use push cuts, with the handle down somewhat to increase the amount of cutting edge in use, never exposing the upper wing edge to the wood. If the gouge is bouncing, go back a bit and start a new cut that undercuts and removes the high spots that are fighting you in a bevel rubbing cut.

[Bob Bergstrom]

Sounds like you could benefit from a little mentoring. Is there a club near you or can you hook up with someone to watch you turn. The cutting angles and body movements can vary from second to second. Maybe set up a video camera and have someone film you. A lot can be learn watching yourself.

[Jake Helmboldt]

As Faust noted, Ellsworth favors the level positioning which can often have more of a scraper effect, the the actual angle of attack will allow a slicing action. As Steve S. noted, Bill's method has a slicing action predominantly. Changing the presentation on either can vastly change how the tool cuts or scrapes, and I think Grumbine's gives you a bit more control and is more likely to cut instead of scrape. I find I get less banging around and a cleaner cut using Bill's method. But you have to work on tool presentation. Even a very uneven blank will result in big thick curls coming off instead of short ones. I find it beats you up less and cuts faster.

[Reed Gray]

Just had a thought, when you drop the handle, you are reaching out farther off the tool rest than if the tool is level. The bounce you get could be part of the extra over hang, and of course, a bigger, heavier tool doesn't vibrate as much.

robo hippy

[David Gilbert]

Terry McCammon said
I have feeling that Grumbine's grind on his gouge is such that this works for him and in fact pushes the tool down on the rest. Is there anyone who can say how he grinds his bowl gouge.


Our woodworking club here in Rochester had Bill Grumbine here to lecture and give a workshop a couple of weeks ago so I had a very good opportunity to look at his bowl gouge's grind. He used a 5/8" Doug Thompson V-grind gouge and his grind looked to me as if it was right out of Doug Thompson's instruction sheet. He was kind enough to regrind one of my gouges and I know that he isn't a slave to a particular Wolverine jig setup. It's pretty obvious that he has enough experience to grind a gouge so that it works.

The point that he made in the demo and DVD was when you are first flattening the bottom, you start at the outside and work in and make small cuts so you don't get slammed by the wood. Only when the bottom has been trued up should you start going all the way across the bottom.

I hope this helps,
David

[Dick Strauss]

Even thoug Bill G calls it a 45/45/45 in the first video, he says it is actually closer to 30/30/30. He made the correction either in person or his newer video "Beyond the Basic Bowl". You have to make slight adjustments to all of the angles (vertical, horizontal and tool flute rotation) until you get it just right for your tool. My tool will require something different based on my nose and wing angles, etc. Once you get it right, you'll start getting a much smoother cut even on interrupted cuts.

Good luck,
Dick