Blew up another bowl

[Anthony Diodati]

Was taking a cut with a 1" scraper, and got a catch, (On inside of bowl) but I had my tip somewhat up, and the handle lower than the tool rest.
I was later reading that I should have my tip down, and my handle raised up higher than my tool rest.
Will this make a big difference in avoiding catches?
What about the tool rest height, on center, below center, above center?
I thought l read the tool rest should be a little above center, and with the handle raised, the burr would be at about center.

Someone said I could grind the scraper to a lower angle than it comes from the factory, since you are not riding the bevel, but then I read a steeper angle, the burr would last longer.

I have to get a bowl gouge sharpening jig made up, as I have been doing most of my turning with a parting tool and a scraper.
I could not get a good grind on the bowl gouge free hand.

Thanks,
Tony

[Reed Gray]

Well, I would guess that you were near the bowl rim, and before it blew, there was some strange screeching and howling noises. Scrapers are great for roughing, but not much of a finish cut tool unless used on end grain turnings, or if used for shear cut/scrapes. When turning the bowl, on the outside, you generally cut at or slightly below center, and on the inside, at or above center. This way, if you do have a catch, the cutting edge will 'drop' out of the wood. I NEVER scrape (scraper flat on the tool rest) on the inside of the bowl any where near the rim after wood has been removed. Main reason is the force of the cut 'pulls' at the wood more than a slice does, and this can make the wood wobble and screech, even with the lightest of cuts. Much wobble = blow up.

If you go to You Tube and type in robo hippy, I have a couple of clips up. 2 of which are turning a bowl with just scrapers, and turning a bowl with just gouges. Hope that helps better than my explanation.

robo hippy

[Dennis Ford]

I sometimes use a scraper as a finish tool near the bottom of a bowl (with the handle level or higher than the tip). Reed is right about using one near the rim, it is a blow-up waiting to happen.

[Chip Sutherland]

Congratulations. I think most everyone can echo this learning experience with scrapers. I rarely use scrapers now. When I do it is on the inside of a bowl, tip down from center and handle up and sometimes radically. A catch at this angle is possible but rare. If it happens the tool is kicked out of the bowl. I've learned that any screeching sounds coming from a cut are the signal to stop what I am doing. They are more common towards the rim.

The most important thing I read in your post was the need for a bowl gouge sharpening setup. I think it is worth your to buy/build one. Turning will be much more enjoyable when you can use your gouges. Robo Hippy's vids are good.

[Jeff Gilfor]

Yes, welcome to the... "I screwed up, and don't want THAT to happen again" crowd. Mistakes in woodturning are inevitable and normal. Just have to learn from them.

I strongly recommend you read this article by Lyle Jamieson: https://www.lylejamieson.com/tools/documents/AAWArticle-FearFactor-Winter06.pdf

It was printed in one of the AAW Journals back in 2005 I think. Anyway, it's probably the best information out there on how to avoid blowing stuff up (or ruining woodturnings)... that is, unless you are a Special Forces guy, and mean to do that.

[Reed Gray]

I would guess that most blow up catches, with either a gouge or a scraper happen on the inside of a bowl. Most of that comes from the shape of a bowl because when in the inside, the tool rest, rim of the bowl, and the bed of the lathe can all interfere with the tools. Best advice for scrapers has been given. Best advice for gouges I can think of is to roll them over on their sides. If the flutes are straight up and down, the wing can dig in. Roll them over from 45 to 90 degrees, and that catch risk is gone.

robo hippy

[Jeff Gilfor]

+1 to what Reed said.

[Anthony Diodati]

screeching and howling.........................No, not really. Actually, I was not at the rim, and not on the bottom, somewhere in between.
Was cutting nice and quiet, then BAM!
I will read this over more tonight, and read the AWW link as well.
So keeping the Scraper TIP DOWN and THE HANDLE UP is important.
What about the angle, will a steeper angle help the burr last longer?
Thanks,
Tony

[Jeff Gilfor]

Big points are:

Rest above center on inside bowls/vessels.
Rest below center on outsides.
Careful orientation of flute to direction of rotation (NEVER straight into the flow of wood).
LIGHT passes, especially nearing the finish of your turning adventure. You can better afford a catch when hogging than when the bowl is only an 1/8 inch thick, and you are just going to "clean up" that one spot.

I find that the burr on the scraper will last as long as it wants to, regardless of the way in which you use it. The type of wood, more than tool presentation, will change the time between refreshing. A CBN wheel will raise a longer lasting burr on the scraper than an AO wheel. A burnishing tool will give a better and longer lasting burr as well.

[Reed Gray]

The burr from the CBN wheels is far better than the one from the AO wheels. Don't know why. I do hone off the old one first. For general roughing, I haven't noticed that the burnished burr is any better or more durable, but I do hand burnish (triangle burnisher, not the round ones) it rather than using the Lee Valley one that you mount on your bench top. Burnisher should be only a couple of degrees off the face of the bevel, so bevel at 70 degrees, and burnisher at 75 degrees. A couple of light passes and you are set.

robo hippy

[Anthony Diodati]

Still goofing with a motor. One I was going to use won't fit.
I just have a old grey one on the grinder down stairs right now. The one here in the Kitchen, (yeah, I'm single............LOL) has a wider white wheel, norton, it's set up for plane irons and paring chisels though.
I do have a sort of blue one, it breaks away easy, but I have not tried it yet.
I will have to look into these CBN wheels.
I have not yet tried to burnish a bevel. All l have though is my round one for my cabinet scraper.
I still got to read all this over better, and maybe work on the bowel gouge.
I guess you said you used a scraper a lot for roughing too.
Will try to comment more later .
Thanks,
Tony

[Jeff Gilfor]

Reed is a scraper magician! Watch his video, in which he turns a bowl from start to finish with just scrapers. Gotta agree with pretty much anything he says... unless of course he's wrong.

[Lee Alkureishi]

Bowel gouge... sounds painful!

[Grant Wilkinson]

Listen to Robo. My scrapers were in the dusty drawer until I watched his videos. Now, I'm darn near as good as he is. :D

[Anthony Diodati]

Listen to Robo. My scrapers were in the dusty drawer until I watched his videos. Now, I'm darn near as good as he is. :D

I liked when he held it on edge, shear cut/scrap I guess?

[Reed Gray]

Yup, when the cutter is at 45 or so degrees to the spinning wood rather than flat on the tool rest, you have a shear cut/scrape. This cut can be done with both scrapers and gouges.

robo hippy

[Anthony Diodati]

Yup, when the cutter is at 45 or so degrees to the spinning wood rather than flat on the tool rest, you have a shear cut/scrape. This cut can be done with both scrapers and gouges.

robo hippy

Does the tool rest height and the handle higher than the tip apply to this cut also?
Is there much chance of a catch with this cut?
I am a bit nervous about catches now.

[Reed Gray]

Tool rest is not super important, but most of the time it is still close to center height. Also, most of the time the handle is held low with the blade being high. Another important part here is when you do this cut, you are cutting with the lower part of the tool (closer to the tool rest part). This keeps that part that is doing the cutting close to the tool rest and balanced. If the tool is at an angle / and you cut with the upper/top part, the tool is not balanced, and it can catch. This is a point that is always made with the skew chisel as well.

robo hippy

[Thomas Canfield]

I have to get a bowl gouge sharpening jig made up, as I have been doing most of my turning with a parting tool and a scraper.
I could not get a good grind on the bowl gouge free hand.

Thanks,
Tony

Tony - This looks like the real answer, getting your bowl gouges to work for you. I seem to have better luck using a sharp bowl gouge for all the outside and inside turning on bowls. Sharp tool really do make a difference, and a sharpening system for most of us is mandatory. The learning cuve for free hand sharpening is much longer than our patience.

[Anthony Diodati]

Yeah, I do have a lot to learn. I have to try to get a sharpening jig made up. Have to work on the motor right now. Think I am going with a VFD and a 3 Phase motor.
Some pretty good prices here. You can get a VFD and motor for under $200.00
http://dealerselectric.com/default.asp

[Anthony Diodati]

Tony - This looks like the real answer, getting your bowl gouge ( I only have 1 right now) to work for you. I seem to have better luck using a sharp bowl gouge for all the outside and inside turning on bowls. Sharp tool really do make a difference, and a sharpening system for most of us is mandatory. The learning cuve for free hand sharpening is much longer than our patience.

I have a Sorby I think it's a 1/2" It had a fingernail grind. Is that an OK gouge?
Do you think the fingernail grind is a good grind?

[ron david]

Was taking a cut with a 1" scraper, and got a catch, (On inside of bowl) but I had my tip somewhat up, and the handle lower than the tool rest.
I was later reading that I should have my tip down, and my handle raised up higher than my tool rest.
Will this make a big difference in avoiding catches?
What about the tool rest height, on center, below center, above center?
I thought l read the tool rest should be a little above center, and with the handle raised, the burr would be at about center.

Someone said I could grind the scraper to a lower angle than it comes from the factory, since you are not riding the bevel, but then I read a steeper angle, the burr would last longer.

I have to get a bowl gouge sharpening jig made up, as I have been doing most of my turning with a parting tool and a scraper.
I could not get a good grind on the bowl gouge free hand.

Thanks,
Tony
perhaps some professional instruction may help.
ron