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Making Scrapers


Nikos Matsablokos

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1 hour ago, bkwood said:

Yes, no flexibility. You don't put a burr on the edge. Sharpen with a quick pass on the grinder and sometimes I smooth the side with a flat wheel and hone.

The finer a polished edge you make (using a whet or water stone will make for better finish scraping. A burr straight off a grinder will be coarse and unrefined. While it will indeed cut, it'll make for rough cutting and resulting in a somewhat rougher finish on the wood because it'll be tearing the fibres rather than slicing them.

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2 hours ago, bkwood said:

Yes, no flexibility. You don't put a burr on the edge. Sharpen with a quick pass on the grinder and sometimes I smooth the side with a flat wheel and hone.

I second @Bill Yacey's opinion. The burnisher, which is used to turn a burr on scrapers, is a smooth rod, which produces a very even and fine burr with smooth edges. If you were to look under a microscope the burr that a grinder leaves, you would probably see a burr, yes, but it would be wavy, chipped and rugged. Scrapers are like planes and though I am used to straight ones that I've been using in woodworking for years, the same applies even more for the ones used to shape and finish a violin. 

A scraper is like a plane. For the same reason that you shouldn't sharpen a plane iron on a grinder (unless of course you only use it to establish the primary bevel) you shouldn't use it to sharpen the scrapers either. Unless maybe if you just use those to hog off A LOT of material.

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2 minutes ago, bkwood said:

Yes, no burr, just sharp edge.

An edge straight off a grinder isn't as sharp as what you think it might be. If you're really interested, I would recommend Leonard Lee's book on sharpening. It's everything you would ever want to know about the subject, and more.

In his book, he shows micro photographs of cutting edges achieved from various sharpening mediums, and a ground edge results in a roughly jagged, torn edge, often with a burr that is folded over.

If you're happy with that, all is well, but you might want to try a highly polished edge and see if it makes a difference in the end result.

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These are a couple of really interesting articles, for those who like the technological approach to understand and see what happens when scrapers are sharpened.

https://scienceofsharp.com/2018/08/22/what-does-steeling-do-part-1/

https://scienceofsharp.com/2019/06/08/what-does-steeling-do-part-2-the-card-scraper/

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38 minutes ago, Bill Yacey said:

An edge straight off a grinder isn't as sharp as what you think it might be. If you're really interested, I would recommend Leonard Lee's book on sharpening. It's everything you would ever want to know about the subject, and more.

In his book, he shows micro photographs of cutting edges achieved from various sharpening mediums, and a ground edge results in a roughly jagged, torn edge, often with a burr that is folded over.

If you're happy with that, all is well, but you might want to try a highly polished edge and see if it makes a difference in the end result.

Thanks. You seem to think I am having a problem with my scrapers, but they work very well and keep an edge. I'm sure a polished edge could only be better but seems unnecessary. I do polish the flat sides. I'll give it a try though sometime, but I tend to sharpen scrapers and chisles and knives until they work satisfactorily and don't over think it too much. I really do like the heavy stiff scrapers compared to card scrapers and it's all I use anymore. I take it you haven't tried them.

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1 hour ago, bkwood said:

Thanks. You seem to think I am having a problem with my scrapers, but they work very well and keep an edge. I'm sure a polished edge could only be better but seems unnecessary. I do polish the flat sides. I'll give it a try though sometime, but I tend to sharpen scrapers and chisles and knives until they work satisfactorily and don't over think it too much. I really do like the heavy stiff scrapers compared to card scrapers and it's all I use anymore. I take it you haven't tried them.

Aside from using chisels and plane blades for scraping, the heaviest bonafide scraper I have used is about .040 thick. For fine work and curved surfaces, I prefer the thin stock.

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20 hours ago, bkwood said:

https://www.stewmac.com/luthier-tools-and-supplies/types-of-tools/scrapers/stewmac-ultimate-scraper/

Here is a link to StewMac's heavy scrapers for anyone interested. There's some information and testimonials. They're not cheap. As I said, they gave me the idea to make a few shapes of my own.

 

I have found these to be terrible on spruce and maple, but absolute perfection on ebony.

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1 hour ago, arglebargle said:

No, they work on spruce and maple. I just don't like the feel and the result. Much better outcome with my usual scrapers. An un-bendable scraper has its place, but not so much on an arched top and back. In my opinion.

 

I got you. Not for everybody.

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