What am I doing wrong?

[Chris Jenkins]

I turned this little bowl out of zebra wood the other night and was happy with the shape, but not the finish. (Didn't start the indside yet cause I'm not happy with the outside)

I sanded to 150 real quick to show the problem areas. Right now I am using a 1/2" bowl gouge sharpened on a wolverine jig and a 3450 RPM 8" 100 or 120 AL oxide wheel.

I think I have to turn the bowl down a bit more to get rid of what looks like a catch (though I don't remember that happening). Can I sand out the chatter / tear out on the end grain? I'm guessing start with the 80 grit gouge.

77500

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[Kevin McPeek]

Looks like some tear out. Have you tried shear scraping it? Sometimes that can help. You can also put a little oil on it to lubricate the cut, I've had that work a few times also. If all else fails bust out the 80 grit.

[Steve Schlumpf]

Chris - that's a hard call. Assuming that you have a sharp bowl gouge to start with there are still a few things that will cause this - at least for me.

Are you allowing the gouge to make light cuts or are you pushing just a little to fast? Are you riding the bevel to hard?
Is the lathe turning at to slow a rate?
Are you using the proper angle of attack with the gouge?

Only you can experiment to find out which - if any - of these may be causing the problem. As far as sanding the tearout - that's going to take awhile and is not always successful. Let us know what you find out!

[Gordon Seto]

I sanded to 150 real quick to show the problem areas.

I think I have to turn the bowl down a bit more to get rid of what looks like a catch (though I don't remember that happening).

There is no sense going to the finer grit until you are satisfied with the coarser grit. Sanding too long with finer grit is wasting your time and run the risk of heat check.

Do you have nicks and dings on your tool rest? They may prevent your tool from gliding along smoothly.

Try to turn one with construction lumber (SPF) from HD and Lowes first. They are the best material to tell you what is right or what is wrong. They are likely to chip, crack, split, tear out and chatter. You can see dramatic difference in results from various techniques.

It is much easier to sand out the tool marks than tear out, almost impossible on chattering.

Bill Grumbine's 1st DVD, "Turned bowl made easy" is a good place to start on the various finishing cuts.

Gordon

[Brian Brown]

If you find that you need to sand the end grain tearout, especially with the coarse sandpapaer, be sure you keep the sandpapaer moving rapidly over the surface, while turning at a slow speed. If you don't. you will get some deep scratches in your work that are very difficult to remove. Stationary paper can cause a large piece of grit to cut deeper than the rest, leaving a scratch that is only amplified by finish. It is best if you have a bowl sander on a stick, a sanding mandrill in a drill, or a ROS to keep the paper moving. I also like to use oil or mineral spirits for lubrication and softening for the scraping action, but it will gum up your sand paper very quickly.

Good luck!

Brian

[Chris Jenkins]

What speed should I be turning this little 6" diameter bowl at? I did this at about 800 - 900.

I'm gonna hit Grumbine's Video again to look at that shear scrape.

[Dean Thomas]

It is much easier to sand out the tool marks than tear out, almost impossible on chattering.
You wrote a mouthful there. Had one late last night that made me mad. Glad that it was not something that had to be exact. Cutting the lid for a birdhouse ornament out of walnut (second round that has to ship TODAY!!!!!). I form the underside and then the top part of the cap itself and then get the "stem" down to about 1/2" so that I can sand. Well, I evidently slept through part of the process or had too much dust on my goggles or something and had to clean up the transition between roof & steeple. Ratzenfratzen. It was too rough to sand so out came the gouge for a return visit. Braced the now flexible piece. NG. DEEP chatter marks. :mad:

Glad that I still had a few 60 and 80 grit gouges laying around. New paper so it did not take too much time. If it had been consistent, it would have been gorgeous, but the grain on that piece was really wild so patterning only showed up on about 40% of the area surrounding the stem/steeple.

But enough about my woes.

Chris, quite a few of what many American turners think of as "the exotics" can be quite chippy. Lacewood and zebrawood are two of them, in my experience. I've turned some of each that were not so chippy, but mostly the stuff that I've touched is pretty sensitive stuff to turn. And I personally think that some of the problems are caused by over-drying the wood before we ever see it. Just like when someone bakes a cake or cooks a roast too long, it just flat dries out and the texture changes for the worse. Had a piece of walnut like that recently. Could get some curls, but mostly dust. It was an even dirtier job than normal.

Shearing cuts are certainly one possibility. One guy shared that he lowers his tool rest and thus the handle of the tool a lot so that the deeply swept back wings of like an irish grind, freshly sharpened, are what somes in contact with the area to be affected. And then super light cuts to produce frog hair curls. If that doesn't help, I'd be tempted to use a scraper--again, freshly sharpened. Actually, since the burr on a freshly sharpened scraper only lasts for a minute or so, I might want to use it, sharpen it, use it, sharpen it, use it, until I got what I was looking for. There's also a new tool out in the last couple of years. I think it might have started with Ray Key. I think it's a sorby product now and presents the scraper's burr at a 45º angle to the work while allowing the square body of the shaft of the tool to stay on the tool rest and be stable. I have a friend in our local club who has one and loves it. Says that it revolutionized scraping for him.

And the whole oiling thing for lubrication might help with any of the above, too.

Oh, another trick from the arsenal... Bob Rosand teaches that when he's dealing with burls and swirly grained woods that he uses a lacquer sanding sealer (or Deft out of the can thinned by half with lacquer thinner) to help stubborn wood to respond better to that final cut.

I think that's all of my inventory of tricks on that subject. Hope SOMEthing helps.

[Gordon Seto]

Oh, another trick from the arsenal... Bob Rosand teaches that when he's dealing with burls and swirly grained woods that he uses a lacquer sanding sealer (or Deft out of the can thinned by half with lacquer thinner) to help stubborn wood to respond better to that final cut.



Our Club had Rosand demo about a year ago, he was using an oil based sanding sealer thinned with mineral spirit.

I find sanding on the chattering usually follows the in and out spirals, I will lose the details, may not be able to see it but other turners can still feel the bumps when taking to the Show & Tell at Club meeting. You know who I am talking about. Those who turn the items up side down and run the fingers across the interior. No matter how nice they said your stuffs are, they will not be buying anything if you are at a craft show either. LOL

Gordon

[Dean Thomas]

Yeah, we know who we are. ;) I admit that I'm one of those. I even enjoy the feel of chatterwork! I just LOVE to touch the stuff and see and feel the creativity that went into it. Good craftsmanship is fun to touch for me.

As for the tools following the bad contour of the tool marks, yes, tis true if you have wide valleys, you're gonna tend to keep 'em, but if the valleys are that wide, it might be time to use a piece of wood with your 60-grit gouge to make the hills low and the rough places plain. Just to give you enough flat surface to actually allow the tools to work again.

And you may have to re-establish the details on a slightly smaller version, but it would save the piece, yes? Unless you're working to match a second to the first. That's part of why matching sets are expensive. One turner said, "Matching pieces? First one is $50, and the match is $500." He may have used other figures, but you get my drift. ;)

[steven carter]

Chris,

When you check out the Grumbine video, you might want to try the 4th finishing cut he talks about. I think he calls it the tangent cut. I have tried it when I have end grain roughness and it seems to work better than the shear cut.

Steve

[Paul Engle]

Chris,
the other thing to watch for is internal check cracks from drying before you got the blank. I did one in Zebra wood 6"x2" and had an unexplained riff like yours shows and could not for the life of me remember a catch. I sanded the whole thing to 320 , the tear out was gone but the line was still there, if you have a magnifing glass or binoculars take a good look at it and see if it is a gouge mark or a split. Gouge mark will be more radial and a split will be more with / along the grain or perpendicular to the grain.Good looking piece and good luck!

[Rob Leslie]

Zebrawood can be a real challenge since the grain changes quite a bit between the bands of colors. Pushing cuts work better for me than pulling cuts. Sheer cuts are also helpful. A very sharp gouge and light cuts (including shear) prior to sanding will probably help clean up some of the "tool" marks. When sanding, be sure to include hand sanding in the direction of the grain (after power sanding) to ensure you get those marks out before going to a finer grit. Hand sand with the same grit (with the grain) following each power sanding step.

Here's a zebrawood bowl I turned earlier this year. In addition to turning, shearing, and sanding; there was a bit of swearing......