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Thread: Negative Rake Scrapers
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15th February 2011, 12:08 AM #1Intermediate Member
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Negative Rake Scrapers
Evening All,
Haven't looked though the old threads but I have been coming across reference lately to Negative Rake Scrapers.
I am after any information anyone may have on them, how to use, why they are better (?) than normal scrapers and how to sharpen.
I normally use all my scrapers in a sheer cut mode ie at 45 degrees as per Richard Raffan's books and lately have even been using cabinet scrapers as a last pass prior to starting sanding at 180 grit.
Am using them all with tool post set at centre height of work or above using the tool in a trailing mode.
From what I gather Negative Rakes are used with the bevel rubbing and in a slicing mode, as per a Bedan tool
Mainly doing bowls and boxes.
Many thanks for any help
Grant
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15th February 2011 12:08 AM # ADSGoogle Adsense Advertisement
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15th February 2011, 06:23 AM #2GOLD MEMBER
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There are many paths to the same place. If you are getting the results you like with the technique you are using, do not be in a hurry to change.
I do not see much difference between trailing a regular scraper and using a negative rake scraper.
Using your scrapers at a 45 degree, you are slicing as much as scraping, which gives a smoother surface.
I will now duck below the battlements while the negative rake proponents have their say.So much timber, so little time.
Paul
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15th February 2011, 08:00 AM #3
"negative rake scrapers" have also been referred to in a kind of "in joke" way! Referring to using a skew as a scrapper. More accurately I guess it referrs to the fact that the top of the scraper is also angled! Can't think what else to say! Haven't had my morning coffee yet!
anne-maria.
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15th February 2011, 09:21 AM #4
If they do, to my way of thinking, they are not using it as a scraper.
My definition of scraping is where the cutting face of the tool is presented at less than 90<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <woNotOptimizeForBrowser/> </w:WordDocument> </xml><![endif]-->° to the wood. My geometry tells me, if the bevel is rubbing then the face of the tool can't be less than 90°.
My most used scrapers have a negative rake which simply helps to more readily decrease the angle between the face of the tool and wood to less than 90°.
.Stay sharp and stay safe!
Neil
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15th February 2011, 04:29 PM #5Senior Member
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A can of worms topic
this links to photos and terms
http://www.hiltonhandcraft.com/Artic...%20Scraper.pdf
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15th February 2011, 04:39 PM #6I do not see much difference between trailing a regular scraper and using a negative rake scraper.
Using your scrapers at a 45 degree, you are slicing as much as scraping, which gives a smoother surface.Inspiration exists, but it has to find you working. — Pablo Picasso
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15th February 2011, 05:29 PM #7Hewer of wood
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There are limited applications where I use a skew as a -ve rake scraper ... say cleaning up a bowl outside, just coming into the foot.
Raffan uses a spear-point scraper for that but I couldn't get the hang of it.
Whatever; with the skew the edge doesn't last long.Cheers, Ern
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15th February 2011, 06:06 PM #8
Yes ern I use the skew the same way for the outside of bowls, find the oval is easiest (for me) to handle. I read Raffan on the spear point but haven't got round to grinding one. Perhaps that cheap Aldi grinder on Thursday?
Michael
Wood Butcher
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15th February 2011, 06:17 PM #9Senior Member
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I don't know where the name came from but surely any tool used as a scraper is presented at a negative rake?
I haven't noticed any real difference in the finish from a normal scraper to that of a negative rake scraper, although a skew used as a scraper seems to take a finer cut. Wether that's due to its sharpness, lack of burr or sharpening angle I don't know.
I do like a scraper with an upper bevel where a bigger overhang is necessary as I feel like I have more control of the tool, especially in a deeper vessel where it is difficult to present a scraper with a trailing edge.
The biggest advantage to me is that because the tool can be held straight on the tool rest, I can usually go from a gouge to the scraper without moving the toolrest.
Best wishes
Steve
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15th February 2011, 08:30 PM #10Senior Member
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In 2005 I attended the Associated woodturners of Great Briton bi annual conference about 250 delegates similar to our Turnfest. An American John somebody had the negative raked scrapers for US $100 undandled yes the looked the part and he could achieve a good result, the same result could be achieved with a normal scraper by rising the handle 10 degres from the normal horozontal angle instead of the cutting surface being 90 degrees to the cut or horozontal it was striking the timber at 80 degrees like a lot of tools it seems to have died a natural death.
Cheers TonyTony
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16th February 2011, 05:14 PM #11anne-maria.
Tea Lady
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Follow my little workshop/gallery on facebook. things of clay and wood.
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17th February 2011, 04:19 AM #12GOLD MEMBER
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