SQ 49 - Negative rake scrapers

[WaggaSteve]

When I got back, I heard everyone raving about reverse rake scrapers and as they sounded easy to make from ordinary scrapers, went for it. Total disaster- wouldnt scrape anything and so I temporarily used my skew on its side to do the same thing (and really its not that different from my idea of the shape of a negative scraper if I am understanding the process correctly).
Finally got cranky enough to convert the converted scrapers back to ordinary scraper shape and they are great, removing heaps of wood and very useful.
What did I do wrong. Note I was sharpening the long edge first then flipping the scraper over to put a small bevel on the other side. Was the order wrong and I was actually blunting the new edge by doing this or is the sharpening process more involved than I thought
TIA
Steve

[Mobyturns]

Negative Rake Scrapers - seems to be a term used to describe any scraper with two bevels. My preference is for a curved scraper with two well defined bevels somewhat similar to a curved skew. http://glennlucaswoodturning.com/product/gl1-negative-rake-scraper/

Like all wood turning tools different scraper profiles suit some tasks and some woods better than others. I suspect you are creating the version with one large bevel & a smaller bevel on the other side. I don't see any real advantage in that style over a conventional scraper but I do see the disadvantages of loosing the burr very easily through poor sharpening technique. http://www.docgreenwoodturner.com/scrapers2.html

[hughie]

the simplest negative rake scraper is the one where you just lift the handle until angle is negative. I have been doing this for years and it works for me.

[_fly_]

you answered your own question.
You don't regrind the top bevel, Its the burr left behind that does the cutting (for a short time).

And the internal angle needs to be less than 90 degrees.
If you get it right it will take timber off in sheets like plane.

here' a bit more explanation.
http://rudolphlopez.com/pdfs/Negative%20Rake%20Scraper%20Jig%20and%20Info.pdf

[dai sensei]

Neg raked scrapers are not for shaping scraping, perhaps that is what you were doing wrong, they are for the last few fine finishing cuts

[Colin62]

Negative Rake Scrapers - seems to be a term used to describe any scraper with two bevels. My preference is for a curved scraper with two well defined bevels somewhat similar to a curved skew. http://glennlucaswoodturning.com/product/gl1-negative-rake-scraper/

Like all wood turning tools different scraper profiles suit some tasks and some woods better than others. I suspect you are creating the version with one large bevel & a smaller bevel on the other side. I don't see any real advantage in that style over a conventional scraper but I do see the disadvantages of loosing the burr very easily through poor sharpening technique. http://www.docgreenwoodturner.com/scrapers2.html

Thanks for those two links, the second one in particular has helped me clear up why I have been battling with my scraping - it's not my new scraper that's somehow faulty, but my burr is too big.

[turnerted]

I grind mine similar to the Rudi Lopez description .
Ted

[powderpost]

the simplest negative rake scraper is the one where you just lift the handle until angle is negative. I have been doing this for years and it works for me.


Agreed...

Jim

[chuck1]

I use the the method taught to me by Mr Hatfield at tafe. just a normal grind and for a finishing scrap I pre hone on bevel face and top face with last hone on grind face to reduce burr for fine cut.
Some will may say I'm stuck in the past but the techniques work well for me.

[powderpost]

Some will may say I'm stuck in the past but the techniques work well for me.

Chuck, I have said it before and I will say it again, the old trade turners solved all their difficulties with thought and innovation. Again in my opinion, the most useful advances have been in the development if steel for tools and electronically variable speed motors. Si then, I am also stuck in the past, to a degree.

Jim

[Mobyturns]

Chuck, I have said it before and I will say it again, the old trade turners solved all their difficulties with thought and innovation. Again in my opinion, the most useful advances have been in the development if steel for tools and electronically variable speed motors. Si then, I am also stuck in the past, to a degree.

Jim

There is still innovation opportunities available - developing techniques to suit the newer tools made possible or available through new materials technology i.e. nano carbides etc. or by adapting technology from industrial metal turning, chucks, spindle development - getting rid of threaded spindles. :rolleyes: I'm looking forward to the day someone develops a commercially viable nano carbide (or similar material) scraper, advancing some of Stuart Batty's tool development.:wink:

Unfortunately we are loosing much of that skills base, knowledge & experience from trade turners. Some of the cr*p :oo: we see on Youtube etc is downright unsafe or only part of the knowledge required to use the demonstrated technique "safely" is communicated.

However I largely agree that production turners developed techniques that were fast, and relatively "safe." Time was money for piece rate turners, so economy of movement, efficient cuts with minimal effort and stress on the turner were soon developed to make more money. Some of their methods are probably considered "unsafe" from a modern health and safety viewpoint, but they were efficient with minimal risk when the turner was well aware of the potential hazards. We still have some hand production turners like Tony Hansen. I would love to see Tony turn in full flight, I've only seen him turn in "slow" mode while demonstrating at Turnfest.