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Grant Mack
15th Feb 2011, 12:08 AM
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

Paul39
15th Feb 2011, 06:23 AM
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.

tea lady
15th Feb 2011, 08:00 AM
:think: "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! :doh:

NeilS
15th Feb 2011, 09:21 AM
From what I gather Negative Rakes are used with the bevel rubbing and in a slicing mode, as per a Bedan tool.


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> <w:DoNotOptimizeForBrowser/> </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.
.

ticklingmedusa
15th Feb 2011, 04:29 PM
A can of worms topic :D
this links to photos and terms
http://www.hiltonhandcraft.com/Articles/The%20Negative%20Rake%20Scraper.pdf

hughie
15th Feb 2011, 04:39 PM
I do not see much difference between trailing a regular scraper and using a negative rake scraper.


some times I's do , sometimes I's don't


Using your scrapers at a 45 degree, you are slicing as much as scraping, which gives a smoother surface.


But mostly I's do this, don't own a negative scraper. But as said above you can get you regular scraper to act as one, beats buying one.:2tsup:

rsser
15th Feb 2011, 05:29 PM
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.

Grommett
15th Feb 2011, 06:06 PM
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?

stuffy
15th Feb 2011, 06:17 PM
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
:)

Tony Morton
15th Feb 2011, 08:30 PM
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 Tony

tea lady
16th Feb 2011, 05:14 PM
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
:)Very good points Steve! :2tsup:

Paul39
17th Feb 2011, 04:19 AM
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
:)

That makes perfect sense.