Sharpening a roundnose scraper backwards

Actually, Walter, it is fairly common to sharpen a scraper backwards or upside down or whatever way you wish to espress it, in order to raise a larger burr. Just incline the grinder table to about 10 to 20 degrees off the parallel and go to it.

It'll give a coarser, presumably longer-toothed burr than conventional face up, but it carries a couple of disadvantages with it. First, it'll be gone sooner, second, while it's there, it'll be aggressive as hell. Might also take a bit more of nose down to engage your burr. Lot of talk about "negative rake" scrapers in other places right now. Must have been an article somewhere recently. With a small reverse grind near the upper surface, they should be more stable than the conventional grind - some bevel to stabilize - making it easier to take a thin broad scrape rather than "shear" presentation with its thin narrow.

Since a smooth edge scrapes as well as a rough one, if not better on fine work, why not go burr-less? Then you hone only.

I bought a round nose scraper from Packard and the instructions that came with it advised sharpening it backwards/upside down. The results work fine for me when taking those final light cuts.

I watched Eli Avisera sharpen his that way.

Right. It causes a burr to form, which does the scraping. The other way to make a burr is to form one using a burnisher. Scrapers remove wood by... scraping, not cutting.

Thank you for responding.

Walter H. Klaus

Hi there

I think we are comparing apples with oranges here, the problem is with the different metals, they do not behave the same under the same conditioning, some will flow better than others depending what and how much other metals are in the steel we have.

Almost all the tool steels are developed for the metal industry, and cutting metal is a lot different than wood.

So rather than going into the metallurgy and guessing what is in your steel, and how it might behave, I would say try to grind the tool first the normal way, and than another way, compare and go from there, my experience with my scrapers is it takes 2 seconds to sharpen and 2 seconds to get them dull again, I don't turn off my grinder if I want to get a fair surface, and take longer between sharpening if I have to just get some bulk out of there.

As for the negative rake on scrapers, it works a lot like holding a scraper with it's nose down steeply, but without getting the tool jammed between the tool rest and the wood, or as using a scraper freehand in the 7 o'clock positioning to cleanup the outside of a turning, just makes for a less dig in prone scraper, thats my take on it.

Have fun and take care Leo Van Der Loo

"Dan Bollinger" skrev i melding news:LO6dnSzKqYBihsfZnZ2dnUVZ snipped-for-privacy@insightbb.com...

(dare, dare not, dare, dare not; oh shit) I would think that to be right, - if they are sufficiently dull. I sharpen my scraper (yes, I have only one) to a bevel of about 80 degrees, and finish the flat side with a diamond hone. It cuts off hairthin shaves with almost no breakage of fibers in the problem spots when presented to the wood like a cutting iron.

I would think, also, that the metal of your scrapers would have to be rather soft to form this burr you are talking about?

BjarteR

I have seen some 'scrapers' sharpened to 60°, but then its no longer a scraper, but a chisel, isn't it? I know of others who remove the burr like you. Still other who remove the burr caused by grinding only to put a burr back on with a burnisher. We know from your description that you are using the tool to scrape, and not to cut, by your description of how you hold the tool (handle tilted upward slightly). Grinding produces burrs regardless of the metallurgy. The size of the burr depends on how your present the steel to the stone.

Dan

Nope. But I do see a pronounced burr grinding them the "standard" (if there is such a thing) way.

But if you're looking for a sharper tool for the finishing cuts, I'm still a really big fan of a carbon steel scraper. They don't stay sharp nearly as long as a fancy HSS one, but boy do they shear fibers smoothly- and they're cheap. I'd worry about a ragged burr from stretching the metal by sharpening upside down, and my inclination is to go with the metal that gets sharper if I want a smoother or more agressive cut.

Then again, there are no set rules for any of this. Give it a try, and let us know how it works.