# negative rake scrapers



## Random Orbital Bob (30 Jun 2014)

Never used one. Any opinions, comments, value judgements from people that have tried them please?


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## woodfarmer (30 Jun 2014)

I have a confession to make. I often use my skew chisel as a straight scraper.

It works fine, if anything easier that the round nose scraper I bought. Much less likely to take a deep cut.

I really haven't yet got the knack of using it as a skew chisel.


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## Wybrook (30 Jun 2014)

woodfarmer":3bry6try said:


> I have a confession to make. I often use my skew chisel as a straight scraper.
> 
> It works fine, if anything easier that the round nose scraper I bought. Much less likely to take a deep cut.
> 
> I really haven't yet got the knack of using it as a skew chisel.




Oh good. I am not alone


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## -Matt- (30 Jun 2014)

Wybrook":2prk25iu said:


> woodfarmer":2prk25iu said:
> 
> 
> > I have a confession to make. I often use my skew chisel as a straight scraper.
> ...




Seconded! Though I sometimes tend to make things out of wood in a "components" sort of fashion so a clean vernier'd step is easy to get with a skew.


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## Paul Hannaby (30 Jun 2014)

I have a couple I used for different things. Both are scrapers I have reground myself. The negative rake makes the scraper less "grabby" because unless you really try hard not to, the edge is presented in a trailing manner.

One down side I have found when using negative rake scrapers is that when using them inside a box, hollow form etc. you can't see where the edge is cutting so it is more difficult to find the exact centre to remove a pip.


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## RogerP (1 Jul 2014)

For small stuff (which is all I really do on the wood lathe) I use one of these HSS Square Lathe Tool Bit Boring Bar Fly Cutters http://tinyurl.com/qcld37w

They come in all sorts of sizes and banged into a handle work very well. Of course they are easily ground, with the correct wheel, to any shape or rake and also the sides can cut well. 

Make a nice tight square hole in a wooden handle and you can swap them end to end with different faces on each. Being HSS they hold an edge very well.


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## Grahamshed (1 Jul 2014)

If you are talking about a second, face, bevel on an ordinary scraper then no, not yet, but Ihave just been watching Mike Waldt's youtube vid about them. They look 'interesting'


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## Spindle (1 Jul 2014)

Hi

I've yet to experience the need for one - I've never had a problem with a normally ground scraper - the harder the wood the easier it is to get a good finish.

Regards Mick


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## Dalboy (1 Jul 2014)

Spindle":156quk4z said:


> Hi
> 
> I've yet to experience the need for one - I've never had a problem with a normally ground scraper - the harder the wood the easier it is to get a good finish.
> 
> Regards Mick



Like you on the whole have no problem except with one scraper Ask SteveF when he came over I will beat it though


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## chipmunk (1 Jul 2014)

One of the nicest applications of a negative rake scraper is when finishing the continuous curve on the inside of a bowl. 

If you try to track a standard neutral rake scraper round the inside curve with a consistent downward tilt on a straight toolrest it's actually quite tough to do. A negative rake french curve scraper flat and level on the toolrest turns this into a breeze.

So, I have one negative rake scraper like this one on top which is a reshaped long and strong 1" skew....







The cross-section is here...






HTH
Jon


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## Vic Perrin (1 Jul 2014)

woodfarmer":28j8lgcq said:


> I have a confession to make. I often use my skew chisel as a straight scraper.
> 
> It works fine, if anything easier that the round nose scraper I bought. Much less likely to take a deep cut.
> 
> I really haven't yet got the knack of using it as a skew chisel.



Looks like one or two of us use the Skew in this mode
:lol: Vic :lol:


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## Spindle (1 Jul 2014)

Hi Chipmunk

Is that technically a negative rake scraper? From your description of it in use it seems to be being used as a normal scraper, your relief of the upper surface allowing you to raise the cutting edge to the centre line and thus improve visual reference but still acting as a normal scraper in it's cutting action.

I understand negative rake scrapers to be used bevel rubbing and have an angle between the upper face and the bevel to be in excess of 90 degrees.

http://www.robert-sorby.co.uk/pdf/hardw ... craper.pdf

Regards Mick


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## Phil Pascoe (1 Jul 2014)

Would that be ground upside down to leave a burr? Would it cut otherwise with an obtuse angle?


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## Spindle (1 Jul 2014)

Hi

See the link - but yes an obtuse angle, (within reason), will continue to cut. Sorby recommends sharpening by honing the upper surface.

Regards Mick


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## chipmunk (1 Jul 2014)

Spindle":1l9w6rsm said:


> Hi Chipmunk
> 
> Is that technically a negative rake scraper? From your description of it in use it seems to be being used as a normal scraper, your relief of the upper surface allowing you to raise the cutting edge to the centre line and thus improve visual reference but still acting as a normal scraper in it's cutting action.
> 
> I understand negative rake scrapers to be used bevel rubbing and have an angle between the upper face and the bevel to be in excess of 90 degrees.



Hi Mick,
I think it is (obviously ;-))because according to my understanding it has nothing to do with the relationship between the traditional bevel and the material being cut but the rake angle relates to the relationship between the leading edge and the material being cut...






A skew held flat on the toolrest is effectively a negative rake scraper because the top edge slopes down if held on-centre.
Jon


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## Phil Pascoe (1 Jul 2014)

Yes, I looked at the link but it showed it in use, not being ground. I suppose its being honed on the top would preclude its being ground with a burr. It's just something I've never come across.


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## Spindle (1 Jul 2014)

Hi Jon

You're at variance with the link I posted and plenty of other info on the web in that case - for instance:

http://www.docgreenwoodturner.com/scrapers2.html

http://www.woodturningdesign.com/askdale/8/8.shtml

http://www.woodturningvideosplus.com/double-bevels.html






Regards Mick


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## chipmunk (1 Jul 2014)

Well Mick I think the definitions are new to me although I guess according to that definition its the same as the top-relieved scraper in your picture. I think the problem I would have with these is that the presentation seems to affect the definition which is a bit weird.

If I rub the bevel with a conventional scraper I think it probably changes its type to something not listed in your pictures? Bert Marsh was a proponent of this and it works pretty well.

The rake angle IMHO is simply the angle, measured from 90 degrees, between the cutting edge and the material being cut. Like this...






Jon


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## Grahamshed (2 Jul 2014)

The video I was watching about it https://www.youtube.com/watch?v=tdXxkr1hEPE is showing a negative rake scraper as being an ordinary scraper with a 70 degree bevel with a top, or face, bevel bevel of 30 degrees added. To my mind this addition turns the tool into a kind of skew though it is used in a different way.
The results seemed good though.


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## Spindle (2 Jul 2014)

chipmunk":1qtdruct said:


> The rake angle IMHO is simply the angle, measured from 90 degrees, between the cutting edge and the material being cut. Like this...



Hi Jon

I know this is bordering dangerously close to semantics but I believe the rake can only be applied to the tool which is frequently demonstrated in metal working tools such as you have illustrated or negative rake applied to twist drills for drilling brass etc.






I've always regarded the type of presentation used when scraping as the tool is in the trail.

Anyhow, terminology doesn't affect how we turn and if it works it's fine :wink:  

Regards Mick


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## Phil Pascoe (2 Jul 2014)

Semantics?
I'm surprised someone hasn't come along to enlighten us. :lol:


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## Random Orbital Bob (2 Jul 2014)

that's why I asked the question 

It appears to me to be rather shrouded in mystery, opinion and nomenclature confusion. I'm not sure I'm any the wiser to be completely honest but I appreciate the discussion.

Mike Waldt's Youtube does give a very clear and definable approach which you can take to the grinder. Also it shows that the practical results are there too. Jon's (Chipmunk) point about the transition from wall to base inside a bowl was what got me started thinking about this. That cut is obviously increasingly tricky with the depth of the bowl and though I've become reasonably proficient at taking very light cuts with all manner of tools including regular scrapers and the same in sheer cut mode at circa 45 deg, a more forgiving tool would always be welcome. So I thought it worth exploring anyway. The input is appreciated.


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## Mark Hancock (2 Jul 2014)

I did some research on this topic a while ago when a new range of negative rake scrapers appeared on the market and the conclusions I came to were:

1. the rake angle is the angle between the tool and the work
2. negative rake is an angle less than 90 degrees
3. a standard scraper (no top bevel) when presented in trailing mode presents a negative rake angle
4. negative rake scrapers (with a top bevel) are usually presented horizontal hence the need to have a top bevel

The whole issue of negative rake scrapers is somewhat confusing because IMHO of the use of terminology and techniques from metal turning being applied to woodturning. 

I can see a use for negative rake scrapers in confined spaces such as the inside of a box but I just don't understand the need on a bowl when simply lifting the handle on a standard scraper gives exactly the same presentation angle to the work... maybe it's just me :roll:

Edit: re the link someone put up to the Sorby scraper instructions....That is the first time in 25 years I've ever seen the advice to rub the bevel of a scraper :?:


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## woodfarmer (2 Jul 2014)

Mark Hancock":29wsd2on said:


> I did some research on this topic a while ago when a new range of negative rake scrapers appeared on the market and the conclusions I came to were:
> 
> 1. the rake angle is the angle between the tool and the work
> 2. negative rake is an angle less than 90 degrees
> ...




+1 it is my take on it also. To my mind a scraper HAS to have its "cutting" edge at most 90 degrees to the work ie scraping, and not on a bevel. Although boning the cutting edge does turn it temporarily into a cutting tool as opposed to a scraping tool.

I use the skew because it came in my only set of tools and that set did not include any scrapers.


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## Phil Pascoe (2 Jul 2014)

That's what I thought. The ability to drop the handle would only really be an advantage (as you say, exactly) in the bottoms of boxes, although for outboard turning of bowls it might make for more comfortable working. I did a small box on Monday, and as my eyes don't work around corners, I was acutely aware of the proximity of the scraper handle to my jaw. I was wondering what a scraper made from a leaf spring would be like - irrespective of grind - would its curve drop the handle too far? 
Just thinking aloud.


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## Mark Hancock (2 Jul 2014)

phil.p":2jnm2zqw said:


> I was acutely aware of the proximity of the scraper handle to my jaw.



That was what put me off scrapers over 20 years ago.....in my case I got a catch and a nice bash on my jaw :roll: Now very rarely use a scraper as I prefer a shear scraping action.


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## CHJ (2 Jul 2014)

I have tried a Negative Rake Grind so that a stiff scraper could be held horizontal on the rest but not found any significant advantage in the way I work, there again 'professional' turners would probably say I do it all wrong anyway.

One aspect I suppose is that presented as such (horizontal) there is less chance of a catch if the handle is inadvertently dropped slightly as the cutting edge may still be in trailing mode.

I can see the advantage on inside curves with a curved sweep scraper with negative rake top face giving a stable tool rest location as opposed to tipping a normally ground scraper.

To me trying to use a negative rake scraper with *bevel rubbing *would be a very limited application, can't think of any instances in recent past where I would have been able to apply such a tool, perhaps there is more application in spindle work, a rare occurrence for me.

What happens if a novice tries to use a negative rake scraper in *bevel rubbing mode *inside a piece? 
Cutting edge would have to be on centre at best, more likely below centre so very prone to dig-in.


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## woodfarmer (4 Jul 2014)

CHJ":2eqvyb11 said:


> What happens if a novice tries to use a negative rake scraper in *bevel rubbing mode *inside a piece?
> Cutting edge would have to be on centre at best, more likely below centre so very prone to dig-in.



It would be virtually the same as using a skew chisel... scary


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