I'm a relative newbie to woodturning and I've run into a problem and don't have my mentor handy to get the solution. Also, I've searched online and haven't tumbled to the answer.
I'm turning a fairly small walnut bowl, ~4" diam. The turning is all done. There are rough patches inside the bowl and on the outside separated by 180 degrees, which are clearly due to tearing of the end grain. I've gone over them with the scraper, and I've sanded. And I've done both procedures again, but the patches are still there.
I know this is a common problem that must be faced and dealt with, but obviously I don't know what next to do.
George, I am also new to turning but have encountered this many times - I turn mostly maple blanks that are very dry, and find there are times that no matter the tool or the sharpness, I still see tear out in certain areas.
Have come to the conclusion that in these cases, sandpaper is the only viable way to fix it.
After spending time convincing myself that its not the method or the tool, I lightly spray the piece with water and let it sit for a few minutes in the hope it will raise the grain ( i admit this could be a mind game I play with myself!) then with the lathe off, I sand back and forth with the heavier grit the area in question.
One I have worked my frustration out,I turn the lathe back on and begin the finishing process again, starting with the grit used to remove the tear out.
Sandpaper for now. Make the next bowl relatively shallow and practice your gouge angles where you can see them clearly. You're looking to have the edge cut across the grain all the way, without getting more than the minimum lift where unsupported. Scraping isn't as well supported as a gouge with a bevel guiding. I get better surfaces with the gouge.
You might try using a standard cabinet scraper in a static mode first. Gooseneck might reach, depending on contour. Spoon type would certainly.
There are a couple of things you can try but it really just boils down to proper tool use and good sharpening. That being said, as a beginner, you (and I) are still working on that and with time will get better. In the meantime, try using some sanding sealer. I'm not sure where you are so I can't give you available brand names for your area. I am in Canada and the best stuff I have found so far is Home Hardware's Sanding Sealer. A good friend of mine who is way past these little tricks and who makes bowls for a living recommended the stuff as probably the best available here. Just put it on, wipe it off with paper towels and let dry a few minutes. It should stiffen the fibers up enough for you to use a well sharpened gouge and just take a small, itty-bitty-teeny-tiny cut all the way through. It works for me. The other solution I have heard of but have not used yet is to coat the area with a little bit of the finish you will be using, wipe off and let dry a few minutes (5 or 10).
You need to understand a bit why this is happening. The fibers you are cutting have no support in that area and they are actually being ripped out of the wood as opposed to sliced off. You need to look for a way to strenghten them up a bit. Sealer or a little oil can often give them that little bit of extra support.
Some areas can be a lot tougher to fix due to the contour of the bowl. If that is the case, a different grind on the gouge or a double bevel can help. As a tool junky myself, I have multiple gouges with different grinds that can accomodate the contours. If you have a very very light touch and a very steady hand, you can achieve a near perfect finish with a scraper but remember that whatever value you place on "very light" and "very steady" is probably about 10 times heavier than what I mean! Practice on a scrap until you can produce whispy whispy strings of wood. I call it angel hair when I teach.
Like everything else in woodturning, practice, practice, practice and never give up. It will all come together.
Works for me.
Mike Courteau snipped-for-privacy@toymakersite.com
George, the best answer to your problem is to use a sharp tool, rub the bevel throught the cut, and cut WITH the grain. Cutting against the grain will result in a bad, torn surface because you're cutting unsupported wood fibers. You need to learn how to shear scrape before sanding. Shear scraping can remove all of the torn surface making sanding much easier.
To shear scrape with a bowl gouge, roll the gouge so the flute is facing the wood. With the handle down a bit and cutting above center, cut with the lower cutting edge with the upper cutting edge very close to the wood. With the handle leading, lightly draw the tool, going with the grain. Apply oil to the wood in the difficult areas. In a very short time you'll have all of the damaged areas cleaned up for easy sanding. A caution: allowing the upper cutting edge to get too far from the wood surface will result in a dig-in.
Or use a forged pattern gouge with the handle perpendicular to the rest so you can get better control than methods which rely on you to support the tool. You can cut below center, so any upward tic takes you into air rather than a catch. Not to mention you can steady on the bevel, too!
A lot of the tips you have already gotten should help. One other thing that I have found useful on torn grain is to rub paste wax into the tear out area then shear scrape or sand. Principle is the same as the sanding sealer but I like the wax better since there's no waiting to dry and no solvent fumes. When I'm sanding and see an area where wax would help, I apply it, sand - and if necessary, wax again- and then continue sanding with the same grit for a bit before moving on to finer abrasives.
George One of the best things you can do is to sharpen well and often, especially before that last cut. Make or buy a jig. Making one is a lot cheaper and not hard. Look for the sharpening section of my web site.
I have run across this often. A tip I read a while back suggested using regular canning wax (parafin). I always had my doubts but finally tried it and it gave good support to the area. I melt the wax in a can on a hot plate and then dip an old toothbrush in the melted wax and brush it into the problem area. Allow it to cool thoroughly and re-try with your tool of choice. I usually move the speed up a click or two and use a very light touch.
A lot of the tips you have already gotten should help. One other thing that I have found useful on torn grain is to rub paste wax into the tear out area then shear scrape or sand. Principle is the same as the sanding sealer but I like the wax better since there's no waiting to dry and no solvent fumes. When I'm sanding and see an area where wax would help, I apply it, sand - and if necessary, wax again- and then continue sanding with the same grit for a bit before moving on to finer abrasives.
I would only add that sometimes when wood has rotted a bit, it will lose strength and grain will tear even with sandpaper, and the options become: seal/glue then either re-turn, or move to the next grit sooner than you would otherwise, if you risk tearing right through the wall. I've had spalted wood where 120 grit takes out gouges bigger than the grains on 40 grit paper. In these cases, no amount of sharpening will help unless the wood is sealed with one of the suggested products, or CA glue.
First solution is that you must use keenly sharpened tools. Try a bowl scraper or a shear scraper, with a slight burr on the edge, and take very light cuts at high rotational speed. Another trick is to lubricate the area, try either mineral oil or something like Briwax or other turner's wax applied to the area then scrape with a very sharp shear scraper. You can also use the side of an Ellsworth grind gouge as a shear scraper.
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