Trouble with Cabinet Scrapers and Bowls

[Matt Schrum]

In short, I am having issues using cabinet/card scrapers on a bowl. In some areas it works well, but then as the grain direction changes along the circumference (coupled with the fact that the bowl is round) I can't achieve good results in other areas.

Long version: I turned a beautiful piece of green wood (I believe oak, but not 100% on that-- free wood is free wood) with some great figure and coloration-- but despite my best efforts with freshly sharpened gouges I still had some tear out in a couple of areas. I knew sanding it was going to be a pain, so I picked up some cabinet scrapers and a burnisher. In the mean time, while the bowl had dried, it also warped quite a bit so I can't put it back on the lathe to clean up the tear out now that it is dry. I filed, honed, and sharpened the scrapers and they work quite well on flat wood. Lots of mini-curlies and a smooth finish. However, I am having a heckuva time on the bowl-- I've barely been able to clean up the tear out. In addition to the fact that it is not flat, the grain direction changes and I think that is what is causing most of my issues in getting a clean finish with my card scrapers.

I know I have seen a few posts where people have noted that they use cabinet scrapers on bowls-- so I believe it is possible. For the life of me though I was unable to find a video or any sort of guide regarding cabinet scrapers and bowls. Needless to say, the search (this forum and YouTube) pulls up a ton of results for scrapers and bowls-- which looks to be drowning out just about everything regarding cabinet scrapers and bowls. Any help or tips would be appreciated!

[Wes Ramsey]

I think cabinet/card scrapers on the lathe are probably a relatively recent development in turning. It is a wonderful idea and has probably been used here and there for many years, but I've only heard people actually admit it just recently. That's probably why there isn't much info out there on this technique. I'd love to watch a video if anyone knows of any.

[Doug Ladendorf]

I'm sure JKJ will be by shortly to help. He has quite a bit of good information posted here and elsewhere on the topic. Are you using a curved scraper? That would help match the profile better. You can also skew the scraper like other tools. Typically you would only use the cabinet scraper without the lathe running. It can get very dangerous otherwise.

Doug

[Doug Hepler]

Matt,

First, to respond to your question -- I have used convex card scrapers on the insides of bowls. In fact, the bowl I am finishing now was scraped that way. You can use the lathe to hold the bowl but do not try to use a card scraper if the lathe is turning the bowl. If the bowl is on the lathe, think about the moment of force when you are pushing on it with the scraper. Depending on the strength of the bowl and the mount you may want to cradle the bowl in some way. Compared to turning, this procedure can be very tedious. It gets easier if you can play with the angle of the burnisher until you get it right for the angle you can achieve while scraping inside the bowl.

Second, it is normal for bowls that were round when green to dry into an elliptical cross section after they dry. IF you left enough wall thickness you can turn it round again and maybe then you could turn out the divots, etc. Turning a hard ellipse into a circle is challenging but it might be a good exercise in turning. I'm no expert in this but you don't want to attack from the side because you will be "cutting air" half of the time, i.e., you can't ride the bevel. You attack from the mouth of the bowl and slice downhill. Excuse me if you already knew this.

Doug

[Bob Bouis]

I've got no real experience using card scrapers on bowls, but my suggestion would be to start like you do finish cutting on the lathe -- i.e., aim for a shear scrape to get a clean cut. Keep in mind that you're scraping 90% end grain and so techniques for scraping with the grain might not work.

Also (if you didn't know already) the usual solution to cleaning up pieces that are out of round is to hit them with a power sander with small (2-3") discs. A proper power sanding setup is fairly inexpensive and makes sanding bowls far less tedious even when they're round enough to sand while spinning.

[John K Jordan]

Matt,

I'm certainly no expert on this but I've been using hand-held scrapers on bowls for a long time, ever since I was driven by desperation and discovered I could smooth an eastern red cedar bowl with a small curved scraper. Heat from sanding was making tiny checks in the wood. I was a beginning turner and this was, I think, the second or third bowl I ever tried:

cedar_bowl.jpg

To be fair, my sanding technique was horrible. I was using too much pressure and too much speed. But the scraper worked where my sanding didn't.

The scraper worked so well that later I got and made some other small scrapers and still use them. I did try power sanding for a while but I far prefer the scrapers to power sanding - I usually get a smoother surface with no clouds of dust. I haven't used my close-quarters angled drill for a long time. (I did recently get a Grex pneumatic 2" random orbital sander but I use this with the lathe off and at a very gentle power.) The whole process got a lot better for me when I learned better tool control for my finish cuts! On a good day my typical method for bowls is finish cut, shear scrape, hand scrape where needed, sand with the lathe off, finish. This is NOT green wood.

I almost always use dry wood, either from the start or turn green and let dry before final turning round. The dry wood is perfectly round so I do use the scrapers with the lathe running, inside and out, but with the lathe turning about as slow as it will go. The success varies. Sometimes the particular wood just does not cooperate and I do something else. Note that if you use a hand-held scraper inside a bowl or especially a closed form while spinning, use a very small one in case you drop it. I remember years ago someone on another forum reported that a large one got away from him with his hand inside a closed form and it turned into a food processor. I tried letting go of a small one, it just droped to the wall and stayed there.

That said about scraping with the lathe on, far more often I use these scrapers with the lathe off. One of the best uses is for removing ripples and center irregularities,both inside and on the bottom. There it is always with the lathe off and scraping with the grain. For winged things made by cutting air the the scrapers are fantastic for cleaning up the inevitable tool marks in the wings, again, of course, with the lathe off. I cleaned up the wings and centers of these with a very gently curved large scraper. I usually remove the chuck from the lathe and work on it while sitting and holding with my knees. I can see and evaluate the surface this way much better then when it is on the lathe.

penta_plates_comp_small.jpg

Scraping is usually with the grain. (Scraping with the grain also means scraping downhill, just like making a finish cut on the inside of a bowl, from the outside in.) If the grain is wild, like the burled walnut piece in the picture, I scrap in what ever direction works!

Note that I normally just remove ripples and tool marks with the hand scrapers. I usually don't try to remove tearout. Tearout from the gouge can be quite deep and the scraping, by nature, removes very little. If I find the hand scraper is causing tearout even when working downhill I may resort to a little thinned shellac sanding sealer or even spritz lightly with water to soften the fibers a bit.

If I do get tearout with the gouge, instead of using the scrapers I work at it with a razor sharp gouge (perhaps honed and polished), take extremely light cuts (which I've heard described as "whisper" cuts), perhaps shore up the wood with thinned sander sealer (or in extreme cases CA glue for punky tearout), and shear scrape with a honed gouge.

I don't have a lot of experience with turning wood green to a finished piece then letting it warp. The times I've done this recently I had good success with a curved negative-rake scraper on the inside - I ground scrapers from Thompson Tools steel. On the outside of a bowl shear scraping with the wing of a gouge usually does the trick.

BTW, when searching I think these scrapers are sometimes called card scrapers, hand scrapers, or cabinet scrapers.

JKJ

[Matt Schrum]

Guys,
Thank you for the information-- this is my first rodeo with card scrapers, so I have a lot to learn still. At the moment I have been using flat scrapers (and only on the outside of the bowl)-- I know curved ones can better match the profile of the bowl, but I was worried that honing and sharpening them would be a righteous pain. I'll look into it a bit more and see what is all involved in keeping an edge (well, hook) on them.

Also, I am aware of turning bowls and leaving enough wall thickness to return-- I've done it a few times, but generally my patience is short enough I like to go the final thickness and see what shape the bowl morphs into. That being said, I do have a pile of bowls in bags waiting to be turned again.

We'll see how it goes and I'll keep you posted if I find anything that works really well, although I just ran into a heckuva deal on some used woodworking equipment that needs a bit of elbow grease, so it may be a few days before I get my shop put back together and pick up the bowl again.

[John K Jordan]

... curved ones can better match the profile of the bowl, but I was worried that honing and sharpening them would be a righteous pain. I'll look into it a bit more and see what is all involved in keeping an edge (well, hook) on them.

FWIW, I dress the flat scrapers with a file. I grind the edge of a curved one simply by rotating it lightly against the wheel while held flat on the rest. (I used to use the Tormek water wheel for this but now I use a 600 grit CBN wheel. A regular grinder works too.)

After grinding, a fine file. slipstone, or a diamond hone makes the edge smooth and removes any grinding burr.

Then I use a hand-held carbide burnisher to roll up the cutting edge. The shaft of a small lathe tool works as well. It only takes a few light strokes or heaver strokes to make one more aggressive. I sometimes refresh this edge with the burnisher several times before I go back to the hone or grinder.

The sharpening method is just like that recommended for a traditional large flat cabinet scraper except I omit the step where I first burnish lightly against the flat of the scraper just before rolling the final cutting edge. I couldn't tell any difference in the result but that step is always taught so it must be for a good reason - maybe I need to experiment more.

JKJ