PDA

View Full Version : negative rake scraper



smiife
17th April 2016, 06:28 PM
Hi guys,
I have heard a lot lately about negative rake scrapers,!
So I found a square ended scraper and thought about
making it in to a n.r. scraper, this is what I have come
up with , but not too sure if the bevel is at the correct
angle or if there is a correct angle? It looks to be about right
at 60ºon the bottom and 15º on the top,
Any thoughts and/or advice would be appreciated

pommyphil
17th April 2016, 06:48 PM
Yes I did one too but I ground mine like a big curved skew, same bevel on each side so I can turn it over. Works well in some applications,377047377048 sorry about the flash. Phil

Cliff Rogers
17th April 2016, 07:06 PM
I have one made from a Sorby 1" skew I found in a sale bin for $10, it is my favourite scraper.

smiife
17th April 2016, 07:56 PM
Yes I did one too but I ground mine like a big curved skew, same bevel on each side so I can turn it over. Works well in some applications,377047377048 sorry about the flash. Phil

Hi phil , so the angle should be the same on each side ?
I made It round so the corners didn, t catch, thanks for your thoughts :2tsup:



I have one made from a Sorby 1" skew I found in a sale bin for $10, it is my favourite scraper.

Hi cliff,
I bought this one from the market place, It is a sorby 1"
just got to make a handle and I will give It a test run:U

Sawdust Maker
17th April 2016, 08:31 PM
what are the alleged advantages?

Mobyturns
17th April 2016, 08:47 PM
what are the alleged advantages?

Like all new wood turning tools - it magically transforms you into a better turner. :rolleyes:

Seriously though a NRS does have a place in wood turning not only for smoothing out ridges off the gouge but also in refining the surface to minimize the amount of sanding required. Once a turner understands how to use the NRS, when a burr is required & when it is not required it can significantly reduce sanding effort and over come a lot (not all) of tear out issues.

george mavridis
17th April 2016, 09:03 PM
Like all new wood turning tools - it magically transforms you into a better turner. :rolleyes:

Seriously though a NRS does have a place in wood turning not only for smoothing out ridges off the gouge but also in refining the surface to minimize the amount of sanding required. Once a turner understands how to use the NRS, when a burr is required & when it is not required it can significantly reduce sanding effort and over come a lot (not all) of tear out issues.

Wouldn't you get the same results using a normal scraper and just lifting the handle so the presentation is at a negative angle?

Cliff Rogers
17th April 2016, 10:56 PM
what are the alleged advantages?
NFI, it is just my fav scraper.
It was a total accident on my part.
I didn't want to waste steel when I ground it round so it ended up with some of the skew bevel left on the end & it just worked a treat for me. :2tsup:

Cliff Rogers
17th April 2016, 10:57 PM
Wouldn't you get the same results using a normal scraper and just lifting the handle so the presentation is at a negative angle?

Yup.

Mobyturns
17th April 2016, 10:58 PM
Wouldn't you get the same results using a normal scraper and just lifting the handle so the presentation is at a negative angle?

George, not quite the same. It is more about the included angle of the cutting profile. Look up Stuart Batty's opinion on NRS geometry. We still have a lot to learn & understand why the NRS profile works. Guilio Marcolongo uses a NRS (i.e. a skew chisel) for hollowing end grain boxes.

turnerted
17th April 2016, 11:01 PM
In addition to what Mobyturns said ,it is virtually impossible to get a catch . I ground mine both sides the same , but I found that I use them more one side than the other so after a while the two sides are unequal .It seems to make no difference . Just be prepared to sharpen frequently.
Ted

Mobyturns
17th April 2016, 11:04 PM
Yup.

Cliff, my original thoughts were the same, however the NRS does not self feed the same way a traditional scraper does when held in trailing mode (i.e. lifting the handle.) I have used a standard skew as a NRS for years as a shear scraping tool on the outside of my small linlam bowls, and a curved skew (Lacer style profile) on the inside. Definitely do not get the same levels of harmonics on thin walled bowls out of kiln dried or very dry timbers that you would experience with a traditional scraper profile. In fact a traditional scraper in trailing mode self feeds and destroys those little bowls almost instantly. The NRS works well for me in that application.

ps I used a modified Sorby tear drop scraper (RS222) insert on the Sorby handle / shaft prior to the NRS. The NRS solved all of the issues I was having with harmonics.

Cliff Rogers
17th April 2016, 11:13 PM
Only difference that I can see is that you don't need the tool rest so high to get the Neg Rake.

What ever it is, it is my fav scraper & it works for me.

Mobyturns
17th April 2016, 11:15 PM
Another benefit in converting a traditional curved scraper to a NRS with equal bevels is that you only require one tool and not two - one for inboard (8007) & one for out board turning (8007LH) or turning in reverse if you feel inclined to do so. Only need to flip the tool and create the burr on the opposite side.

Cliff Rogers
18th April 2016, 08:32 AM
I tend to use mine for inside & use the bottom wing of a bowl gouge rolled on its side on the outside.

Mobyturns
18th April 2016, 08:55 AM
Perhaps I over think things at times but I like to consider and observe what is really happening when we use a tool. I look at things such as the presentation angle we "traditionally" use, sharpening angles, position of the cutting / scraping portion of the tool that is actually doing the work relative to the horizontal plane at tool rest height and the work piece.

It seems to me that most turners use a traditional scraper in trailing mode with the tool rest set so that the business end / cutting portion of the scraper is "below center" they are creating an opportunity for a catch.

If the tool grabs / catches it feeds into more timber rather than bounce clear. I have learnt to use traditional scrapers in trailing mode with the tool rest set much higher than "normal" for cutting with the gouge, so that the business end is cutting at or much preferably slightly above center. My height makes this easier to do but is quite uncomfortable for shorter turners.

smiife
18th April 2016, 08:39 PM
It would seem there are divided thoughts on this matter
depending on who you talk to , some fore , some against
I think I will leave it as is , make a handle and just suck it
and see, will try it out and adjust the angles accordingly:C

george mavridis
18th April 2016, 08:44 PM
It seems to me that most turners use a traditional scraper in trailing mode with the tool rest set so that the business end / cutting portion of the scraper is "below center" they are creating an opportunity for a catch.

I was shown to lift the rest above centre and have the scraper angled down it hits the timber at centre. That gives you a negative angle between the tool and the wood.

powderpost
18th April 2016, 09:25 PM
I don't think it is a secret that I by and large stick to traditional tools and methods for what I do on the lathe. Over a lot of years, new methods and tools turn up and adopted by turners in the hope that they will become expert turners immediately. It is a bit like learning to type, you have to learn the basics before you can become proficient, as it is for turning. Many people do not take the time or the effort to learn to use tools in the more traditional method.
Negative rake scraping is still scraping and will tear the surface of the some woods. Today I spent some time today using a negative rake scraper on some cedar, it made a hell of a mess of the surface of the wood. I also used it on some gidgee and a few species in between. The harder woods were quite ok and did produce a nice shaving. I then tried a shear scraping technique on the same species and found a better finish on the softer species and an unsatisfactory finish on the harder species.
Then I did the same exercise with what are called "traditional" scrapers and methods and couldn't detect any advantage in using a negative scraper technique, but that does not suggest that negative rake concept is no good. The bottom line is that if it works for you and you are enjoying what you are doing, then all is good.

Jim

Phily
18th April 2016, 09:26 PM
That's an interesting question George, I remember going to a Richard Raffan workshop with my new SB negative rake scraper. Before I even took it out of its package Richard commented on the hype around NR scrapers, his view being that lifting the handle gives the same result. I left the SB in its package! Personally however I am more comfortable using a NR; somehow it feels uncomfortable lifting the chisel angle so high on normal scrapers - though no doubt it wouldn't take long to become comfortable.
By coincidence I have just ground a new NR scraper which I have named Dr Evil as it has a wicked curve. Its designed for use with resins which need extra care to avoid catches (the resin shatters). I guess its a case of each to their own with no right or wrong. Cheers Phil

Mobyturns
18th April 2016, 09:38 PM
Powderpost sums it up pretty well, the performance of the tool is very dependant on the properties of the timber being turned. I haven't had a lot of success with NRS's on softer timbers like red cedar.

Woodturnerjosh
18th April 2016, 09:55 PM
Yes, NRS's are useless on soft timbers and I find regular scrapers leave a better finish but on very dense timbers I find them fantastic.

I'm surprised that people don't find a difference to using them compared to regular scrapers though? I can use my NRS several inches over the tool rest with no grabbing and no vibration on thinner walls...I find a cut this smooth and controlled impossible with a regular scraper extended 3+ inches over a tool rest...maybe I'm missing something

smiife
19th April 2016, 08:46 PM
That's an interesting question George, I remember going to a Richard Raffan workshop with my new SB negative rake scraper. Before I even took it out of its package Richard commented on the hype around NR scrapers, his view being that lifting the handle gives the same result. I left the SB in its package! Personally however I am more comfortable using a NR; somehow it feels uncomfortable lifting the chisel angle so high on normal scrapers - though no doubt it wouldn't take long to become comfortable.
By coincidence I have just ground a new NR scraper which I have named Dr Evil as it has a wicked curve. Its designed for use with resins which need extra care to avoid catches (the resin shatters). I guess its a case of each to their own with no right or wrong. Cheers Phil

Hi phil,
Thanks for your reply, do you know what angle
your nrs Is ? and are angles the same on each side?

Jeff Leslie
19th April 2016, 10:25 PM
I mean no disagreement, but if you watch say Vic Wood with a very aggressive (say a 15 degree scraper with no burr), you will see the benefits of a NRS for those on L and P plates.

It is quite confusing and, at least for me, dependent on the steel. My P & Ns with the shape of my Hamlet NR scrapers do not work as well. Make the P & Ns angle more pointed and you get a better result.

Can someone explain it to me?

Mobyturns
20th April 2016, 07:58 AM
I mean no disagreement, but if you watch say Vic Wood with a very aggressive (say a 15 degree scraper with no burr), you will see the benefits of a NRS for those on L and P plates.

It is quite confusing and, at least for me, dependent on the steel. My P & Ns with the shape of my Hamlet NR scrapers do not work as well. Make the P & Ns angle more pointed and you get a better result.

Can someone explain it to me?

Jeff, I'm still learning about NRS's myself, about all tools in fact as I don't believe we ever stop learning new or better ways to use them.

For every well informed opinion I have heard or read about the benefits NRS's there appears to be another just as compelling opinion as to why they don't work well. We have turners like Stuart Batty who insist that the burr does the cutting and that the burr must be maintained, then we see Guilio Marcolongo hog out the inside of a lidded box in something like Gidgee with a 3/4" or 1" traditional skew used as a NRS and no burr. Or a master like Vic Wood smooth a wave box ....

I like to try different things and must admit that for many years that I have used a 1/4" and 3/8" "parting tool" in the same manner that Guilio does. It works without a burr! It also works better with a burr at times for light finishing cuts. I have also used a traditional skew as a negative rake scraper on the outside of bowls for many years both flat on the rest and angles up in a shear scraping mode; and a curved one on the inside, but not in shear scrape mode - bit too risky for me. I know that NRS's work both with & without a burr BUT only on some timbers. I also know that the NRS will perform as Josh mentions above no or very minimal vibration on thin walled bowls compared to a traditional scraper & much less risk of blowing up the vessel.

In most hands both traditional scrapers and NRS's will out perform a bowl or spindle gouge in end grain hollowing until you see a turner like Richard Raffan hog out a lidded box with a spindle / detail gouge.

Many of us have done these things - we know they work - but it is not one universal truth. Each will / may work in a particular scenario, i.e. bowl / vessel form + wall thickness + timber + presentation angle + tool profile & the way you hold your mouth on the day. You know, we all have those days when it all goes swimmingly or to $h!t.

Paul39
20th April 2016, 10:37 AM
Many of us have done these things - we know they work - but it is not one universal truth. Each will / may work in a particular scenario, i.e. bowl / vessel form + wall thickness + timber + presentation angle + tool profile & the way you hold your mouth on the day. You know, we all have those days when it all goes swimmingly or to $h!t.

The above is the absolute truth.

Some years ago I read that Richard Raffan had made over 30,000 bowls. With that much practice one learns how to hold your mouth right.

Phily
20th April 2016, 12:24 PM
Hi phil,
Thanks for your reply, do you know what angle
your nrs Is ? and are angles the same on each side?


Hi Smiife, I've ground the NRS at 45 degrees each side of a centred edge. I've played around to try and get the best cutting edge; a sharp edge with no burr through to a substantial burr using a burring rod. In the end, my favourite edge has been achieved by drawing the chisel through a knife sharpener (see photo), gently finishing with an oil stone then giving the edge a very gentle rub with the burring tool (polished steel rod). With the tool rest above centre only a slight angle on the handle is required to achieve a fine, clean scrape (ref photo - though note this was just a quick scrape of the first thing that came to hand - the timber finish could be finessed a bit more!). The blade shape of the chisel also offers a range of angle options - and of course the burr can be applied to either side of the edge.
377232377231

NeilS
20th April 2016, 05:50 PM
Pattern makers have been using NR scrapers for ever.

The retired pattern maker who comes to the local men's shed, who is well into his eighties, scrapes everything.

I rarely use anything else other than a NR scraper when I'm scraping. Did so for decades before anyone began naming them as such. My scrapers were so extreme compared to traditional scrapers that I got polite non-comments when I first admitted to the error of my ways on turning forums about a decade ago... I was obviously too far gone to warrant correction... :U

What hasn't been discussed here is the value of bringing the top bevel to a high polish. Also the benefit (or not) of burnishing the burr if you retain it.

Alan Lacer discusses both here (https://books.google.com.au/books?id=MJmYCAAAQBAJ&pg=PA36&lpg=PA36&dq=burnishing+the+burr&source=bl&ots=x-Fli1K5wk&sig=YcRjpUmroHf4EUZMRsQ9T95MR18&hl=en&sa=X&ved=0ahUKEwiP3KHgvpzMAhWiXaYKHQtpCpYQ6AEIPDAH#v=onepage&q=burnishing%20the%20burr&f=false).

In my experience a high polish on the top bevel (and also in the flute of gouges) is very beneficial and burnishing the burr adds strength to it. I burnish with a handheld diamond plate (it being a much harder material than the metal in the scraper) and that also serves to raise a fresh burr at the same time. I don't need to leave the lathe to do this, the diamond plate always being in my pocket.

I fragile burr is next to useless as it only last microseconds before it is gone, in which case you would be better off honing it away and at least leaving a firm but less acute edge. That is not to argue for removing the burr as much as the benefit of hard burnishing it.

Here is a thread (http://www.woodworkforums.com/f8/brief-history-burr-131073) that I ran some time ago in which I reporting on my experiments on these two aspects of scrapers.

Jeff Leslie
21st April 2016, 09:01 PM
I have read a good many posts on this forum but none - at least for me - have been as beneficial. What we all do with our tools (and tool work) is worth passing on.

Now Geoff, I attended the Phillip Island Turnaround (as always) in 2014. At maybe 11pm, in the hall, I remarked to Guilio Marcologongo that I had some difficulty in acquiring one of his boxes with an off-set lid. That basdar#d Neil Ellis always out-bid me on the sale table.

After I mentioned that, and typical of Guilio, he promptly got a lump of Dead Finish out...... And proceeded to hollow the box with a 10-12 mm parting tool/skew. It took him about 20 seconds to hollow, another 2 minutes to finish. I now have a Guilio box cost free. I do owe him a favour though.....

I was, in short, horrified but impressed without question. (I might add that no one can turn jam chuck faster than Guilio IMHO).

Our club - the Albury Wodonga Woodcrafters - will have the pleasure of a Guilio M. demo in late May. Ken Wraight is riding side-saddle for the two days, so we are gifted. I am good friends with both, so the balancing act will be a true test. And I have both in my shed before and after for a week....... I am blessed.

After I talk with Retired and Vic Wood, I will report further. I just have to hook my Clearvue cyclone up to my lathes....

Mobyturns
22nd April 2016, 09:31 AM
Jeff,

I am the proud owner of two Guilio boxes, one in Dead Finish and another in African Blackwood. :D I watched the Dead Finish box being made while Guilio was in slow down demo mode so we could actually see what he was doing. :rolleyes: No doubt that he is a master at hollowing with a skew. I only wish I was closer so I could attend this weekend. You are very fortunate to have access to Guilio, Ken & Vic, all three are outstanding turners and fine gentlemen to boot. Say Giday to Helen for me as I guess she will be there too.