How to deal with tearout?

[Dave Mount]

I find that all other things being equal, I get more tearout on the outside of a bowl than the inside from the primary shaping cut using a conventionally presented bowl gouge. I suspect it has to do with using a marginally supported pull cut to shape the outside of the bowl and a well-supported push cut on the inside.

Agree with Reed on a shear scrape using an inverted bowl gouge with the wings ground back as the easiest/most consistent way to removed tearout on the outside of a bowl. It's also the tool already in my hand. If I have tearout on the inside that needs to be addressed, I switch to a 5/8" U flute bowl gouge that is not ground back very far on the wings (my primary shaping gouge is a V flute). Present the tool with the flute fairly closed and the broad curve of the cutting edge gives you a nice shearing cut, and it is simultaneously good for getting a fair curve around the inside "corner" of the bowl.

I know it's kind of "yada yada," but the "sharp tools light cuts" mantra exists for a reason.

Best,

Dave

[John K Jordan]

..So the Thompson tools are hardened all the way down? I've heard some tools are only hardened so far down from the tip.

Doug Thompson said he machines the 10V steel then sends a large batch off for heat treating. I understood the entire tool is treated and my experience with grinding on the end confirms that, at least on those I've tried. I buy round rod from him too with no machining (to make tools) and it's also hardened completely.

In general, the Thompsons are my favorite tools. The 10V steel is excellent and seems to hold an edge longer than Sorby, Crown, and other tools in my stash.

I'm familiar with some tools that are only hardened at the tip. I have a tub of used tools I buy or am given and save them to give to students or starving turners or to regrind into special tools. I test each one with a triangular file. (For those not familiar with this, just try filing a small v-groove on the tool - it it's hardened steel the file will skate on the steel and not cut at all.) Some cheap tools are only hardened for the first inch or so. Once you grind past that you're out of luck. I found some not hardened at all!

JKJ

[Brian Deakin]

I live in the United kingdom and a number of months ago I had a conversation with a Sheffield tool manufacturer

He explained the reason for leaving a small portion of the tool shaft at the handle end unhardened was a safety feature
The rational is if you have a catastrophic event with a tool having a small portion of the shaft unhardened this allows the tool fail and is regarded as a safer option than having the entire length of the tool hardened

[Steve Mathews]

I am wondering why you had more tear out on the outside of the bowl than on the inside. Most of the time, if I am having tear out problems, it is the same on both inside and outside. I would guess that you might be using more of a scraping type cut on the outside, and more of a shear/slicing cut on the inside. I have only turned a couple of pieces of magnolia, co don't really know it...

I generally don't like the NRS for most bowls. Partly because it is still a scraper, and partly because, most of the time I can get a better surface with a shear scrape. I do have one video dedicated to that, on You Tube... Some of the softer woods that tear out when you turn with gouges don't work well with the NRS either. Most of the time the harder woods do better, it just depends.

robo hippy

Thanks Reed for reminding me about your excellent video on shear scraping, one of your best IMO. I watched it a few times more and applied the technique to the bowl. A bowl gouge was used and it helped a lot. The imperfections that I wasn't able to remove were tackled with my usual standby, grunt sanding. I'm almost finished with it now and I have to say this is the largest bowl (13" in diameter) and most difficult thus far.