finish scraping

[Kevin Jenness]

Having started this thread I suppose I should put my cards on the table. I seem to have acquired a largeish number of scrapers, most of them gifted and repurposed, mostly negative rake scrapers.

The small scrapers on the left are single-purpose tools for shaping square and dovetail tenons, the next is a standard box scraper, and the fourth I sometimes use for shear scraping convex forms - all have a flat top surface. The rest have a negative rake, mostly 21* on top and 62* below, keeping the included angle under 90* and odd angles because that is what I get with my RoboRest setup. I have tried removing and re-raising a burr on these tools but have reverted to using the burr off the grinder. The Drozda box scraper and the gooseneck tool on the right have an included angle of about 45*. The three tools at center are 1/2" thick, reassuring when reaching off the toolrest (but the previous owner of the long skinny tool bent it inside a hollow form!). The teardrop on a Jamieson mount at bottom left is used on every hollow form- I have used it only flat, but I will try rotating it for shear scraping as Neil S described above.

I'm not sure how important the top angle is. I suspect that a smaller included angle dulls more quickly and that an obtuse angle would make producing a good burr difficult. I eagerly await the forthcoming scientific study on scraper steel and angles.

The StewMac hand scraper is invaluable for spot cleanup and smoothing out carved surfaces, thick enough to give it some authority and with a variety of curvature. It's used with the grinder burr. The card scraper is rarely used for turning but handy occasionally for getting at sharp inside corners. I usually polish off the grinder burr and raise a fine burr with a carbide rod on this one, but sometimes just use the filed edge. The last two are used strictly with the piece stationary. The little cabinet scraper is for flatwork and I include it just to show a very effective negative rake scraper with no burr at about a 5-10* variable angle.

When I shear scrape it is always on convex surfaces and usually with a swept-back bowl gouge. I will have to try shear scraping on interiors. I reach for the negative rake scrapers more often and I frequently spray a bit of water on the surface to soften the fibers. I seem to get different results with the same tool and approach on different types of wood as Robo Hippy suggests, so I distrust categorical statements like "Shear scraping yields a better surface both on the inside and outside of a bowl."

I have to disagree with the idea held by some that negative rake scrapers are the equivalent of a standard scraper held at a downward angle. That may be true in a specific case but when a scraper is held at an angle other than flat the effective angle of the edge to the wood changes with the distance off the tool rest. An NRS allows for holding the tool level with a constant negative attack angle relative to the work.

Thanks for all the responses. I always learn something from a thread like this, both about tools and about people's approaches to turning (and posting).

 

[Webb Willmott]

How long does a burr on your scraper?

 

[Holmes Anderson]

Having started this thread I suppose I should put my cards on the table. I seem to have acquired a largeish number of scrapers, most of them gifted and repurposed, mostly negative rake scrapers.
View attachment 75657
The small scrapers on the left are single-purpose tools for shaping square and dovetail tenons, the next is a standard box scraper, and the fourth I sometimes use for shear scraping convex forms - all have a flat top surface. The rest have a negative rake, mostly 21* on top and 62* below, keeping the included angle under 90* and odd angles because that is what I get with my RoboRest setup. I have tried removing and re-raising a burr on these tools but have reverted to using the burr off the grinder. The Drozda box scraper and the gooseneck tool on the right have an included angle of about 45*. The three tools at center are 1/2" thick, reassuring when reaching off the toolrest (but the previous owner of the long skinny tool bent it inside a hollow form!). The teardrop on a Jamieson mount at bottom left is used on every hollow form- I have used it only flat, but I will try rotating it for shear scraping as Neil S described above.

The StewMac hand scraper is invaluable for spot cleanup and smoothing out carved surfaces, thick enough to give it some authority and with a variety of curvature. It's used with the grinder burr. The card scraper is rarely used for turning but handy occasionally for getting at sharp inside corners. I usually polish off the grinder burr and raise a fine burr with a carbide rod on this one, but sometimes just use the filed edge. The last two are used strictly with the piece stationary. The little cabinet scraper is for flatwork and I include it just to show a very effective negative rake scraper with no burr at about a 5-10* variable angle.

When I shear scrape it is always on convex surfaces and usually with a swept-back bowl gouge. I will have to try shear scraping on interiors. I reach for the negative rake scrapers more often and I frequently spray a bit of water on the surface to soften the fibers. I seem to get different results with the same tool and approach on different types of wood as Robo Hippy suggests, so I distrust categorical statements like "Shear scraping yields a better surface both on the inside and outside of a bowl."

I have to disagree with the idea held by some that negative rake scrapers are the equivalent of a standard scraper held at a downward angle. That may be true in a specific case but when a scraper is held at an angle other than flat the effective angle of the edge to the wood changes with the distance off the tool rest. An NRS allows for holding the tool level with a constant negative attack angle relative to the work.

Thanks for all the responses. I always learn something from a thread like this, both about tools and about people's approaches to turning (and posting).

I agree that different tools and techniques produce different results in different wood and even different blanks of the same species. Shear cuts can definitely generate a surface as good or better than a shear scrape at times, but I would be surprised to see a NRS produce a better surface on full-on endgrain than a shear scrape. It's basically like a helical JP cutter versus a straight cutter in terms of tearout.

 

[Kent Reisdorph]

How long does a burr on your scraper?

A few minutes of cutting time, I would guess. I raise the burr with a burnishing tool 5-6 times before going back to the grinder.

 

[Kent Reisdorph]

I have to disagree with the idea held by some that negative rake scrapers are the equivalent of a standard scraper held at a downward angle.

I agree. Some of the worst catches I have had have been with a Fench curve scraper held at a downward angle. I'm fixin' to make that one negative rake scraper. Maybe NR scrapers are training wheels, but I'll take them all day long.

 

[robo hippy]

I had considered that holding a standard scraper at a more downward angle would equal a NRS, but that is not the case. Ed Webber, who was the moderator over at Woodturner's Resource explained that what you get is a "trailing" cut. Explained, if you use a card scraper, you ease/angle it forward until it starts to cut. If you angle it too far, it will still cut, but the cutting edge is acting more like a rake so you get more tear out rather than less. That does make a certain amount of sense.

For edge durability, the grinder burr on my Big Ugly tool will generally last half a day or an hour or three. The tantung is a bit brittle, so it does not burnish well. For my NRSs on M42 or V10 scrapers, they will last at least for one bowl, and if I burnish it down and back up, I can get several bowls out of one sharpening. This is highly dependent on the wood. I have been turning some bay laurel that I can only get clean cuts on with my gouges. A NRS, standard scraper, shear scrape all leave rougher surfaces. A buddy who got a log from the same landing mentioned that his log was forcing him to resharpen more often. Just this particular logs I guess....

robo hippy

 

[Jon Rista]

I have to disagree with the idea held by some that negative rake scrapers are the equivalent of a standard scraper held at a downward angle. That may be true in a specific case but when a scraper is held at an angle other than flat the effective angle of the edge to the wood changes with the distance off the tool rest. An NRS allows for holding the tool level with a constant negative attack angle relative to the work.

There is definitely a difference. There are two key factors with a scraper: The top angle presented to the wood, and the direction of force of the tool applied to the wood.



With an NRS, the angle presented to the wood is downward, but in a normal orientation the force of the tool into the wood is strait in/horizontal.

With a downward angled standard scraper, both the angle of presentation and the direction of force of the tool are downward.

From what I understand about the physics here, angling a scraper downward, even though it presents a negative angle to the wood, the downward angled force actually counteracts the angle presented to the wood, but together both result in the wood wanting to "climb onto the scraper" even more, than if the scraper was kept flat and presented to the wood normally. In my experience, a downward angled standard scraper tend to grab more, especially as I transition into the "corners" of the inside slope of a bowl, and it will bite out more of the wood if I am not extremely careful. You can certainly learn a skill to handle this, and gain control, but there is always the higher risk that a scraper presented this way is going to take a bite out of the wood. Managing the risk vs. the risk always being present. You have to put thought into managing that risk, while ALSO using the tool effectively for its purpose.

With an NRS, the scraper is generally kept flat, so the force is strait into the wood, while the wood itself glides off the negative angle of the top edge. This reduces the desire of the wood to climb onto the scraper, something a downward angled standard scraper cannot actually do. This eliminates the risk of the scraper biting the wood like a downward angled standard scraper, meaning you don't have to manage that risk, you can focus on using the scraper effectively for its purpose.

 

[Doug Freeman]

I have to disagree with the idea held by some that negative rake scrapers are the equivalent of a standard scraper held at a downward angle.

Agreed. Its not actually a debate, though some think so. A flat top scraper would need to be angled 20* to be equivalent to an nrs with a top angle of 20*, etc for whatever the nrs top angle is. Holding a flat top at 5* is not the same as an nrs 20* top angle.

It’s all about the angle of attack of the burr as presented to the wood. The greater the top angle of the nrs, the less positive angle the burr has in relation to the wood, ie the more the top surface is angled the less aggressive the cut (everything else being the same).

 

[Doug Freeman]

From what I understand about the physics here, angling a scraper downward, even though it presents a negative angle to the wood, the downward angled force actually counteracts the angle presented to the wood, but together both result in the wood wanting to "climb onto the scraper" even more, than if the scraper was kept flat and presented to the wood normally.

The end result is the same, but I describe it differently. The wood does not “climb onto the scraper”, rather the vertical force generated by cutting develops a force vector inline with the tool, pulling the tool into the wood. The greater the angle the flat top is held downward, the larger the force vector inline with the tool is. This is offset by the decreasing angle of attack of the burr which decreases the cutting force.

With either flat top or nrs held flat, the tool rest opposes the cutting force vertically. The flat top burr, though, has a greater angle of attack, which pulls the edge into the wood.

 

[Jon Rista]

The end result is the same, but I describe it differently. The wood does not “climb onto the scraper”, rather the vertical force generated by cutting develops a force vector inline with the tool, pulling the tool into the wood. The greater the angle the flat top is held downward, the larger the force vector inline with the tool is. This is offset by the decreasing angle of attack of the burr which decreases the cutting force.

With either flat top or nrs held flat, the tool rest opposes the cutting force vertically. The flat top burr, though, has a greater angle of attack, which pulls the edge into the wood.

Yeah, that's why I put "climb onto the scraper" in quotes.

There is more to angling a standard scraper down, though, than just this. You have to hold it at that angle, and I think part of the reason its more risky, is you have to counteract the force of the wood pulling on the tool, which you do by pulling the handle down. Further, holding the handle up like that, is a bit unnatural, requires kind of cricking your wrist at a less than optimal angle at best, which probably introduces an unsteady factor in holding the handle at the right angle as well. There is a fine balancing act there, and if you pull down too hard, the arc that the scraper wants to sweep when you pull down on the handle, wants to drive into the wood even more. I think this, combined with the force of the tool already getting pulled into the wood, makes grabbing an unduly large bite out of the wood, leaving some kind of divot to some degree, a much greater likelihood (i.e. greater risk) than if you were using an NRS presented flat/strait into the wood. The NRS doesn't require that balancing act of keeping the scraper at a steep angle or the counteracting finely balanced forces of holding the handle at an odd angle oddly with your wrist in an odd orientation.

 

[robo hippy]

Maybe it is because I use them so much, for ALL of my roughing, that I have never noticed "self feeding". Big, as in wide and thick, are just too much metal, and the potential for too much metal getting into the cut increases in a big way. There is not a more efficient tool for roughing out bowls as near as I can tell.

robo hippy

 

[John Whitley]

re-sharping to a keen edge is so quick and easy (only seconds of time, as a matter of fact)

On this point, I'll reflect that one of the earliest and best bits of turning advice I took to heart, before I'd even learned to turn (just planning that area of the shop), was to have the grinder right next to the lathe. Step, step, now I'm sharpening.

 

[Jon Rista]

Maybe it is because I use them so much, for ALL of my roughing, that I have never noticed "self feeding". Big, as in wide and thick, are just too much metal, and the potential for too much metal getting into the cut increases in a big way. There is not a more efficient tool for roughing out bowls as near as I can tell.

robo hippy

Maybe self feeding isn't the right way to describe it. Thinking about when I used to hold my standard scrapers at a negative angle...I think the problem is really more of a manual control issue. If you are skilled enough to keep the scraper at just the right angle, then, it will probably work ok? Considering my own experience, when I get one of those bites, leaving an arcing divot, I think its usually because I pulled the handle down. Even just a little, and you can quickly screw up the process.

Further, again just in my own experience, I've found it a heck of a lot easier to hold an NRS (or even a standard) scraper FLAT, rather than at an angle. Its pretty much effortless. Which seems in fairly stark contrast to holding any scraper at a negative angle. There is a more explicit effort required to keep the handle up, and at just the right angle. But this is in addition to moving the scraper along the path you want to scrape too...

Another issue I've had with holding a standard scraper at a negative angle...is you also limit your path options. As you drag the scraper along a path, say from center of a bowl to the rim. At the center, you can maintain say, a -20 degree angle, but as you move the scraper towards the rim, you usually have to bring the angle up in order to continue scraping. The tool rest doesn't allow the same kind of negative angle, the more the scraper is turned towards the rim, right? Now, perhaps you start tilting it, and begin sheer scraping instead... But that's a different kind of tooling then...

So, thinking about all of this, I think its less an issue of "self feed" and more limits on tool control when you try to maintain the tool at a negative angle. The rest itself, the angle the tool must be held at, counteracting forces, limitations on angle or shifts into different tool orientations... I think those lead to greater risk of problems, biting into the wood, when holding a standard scraper negative, vs. just using an NRS flat.

 

[John Whitley]

If you are skilled enough to keep the scraper at just the right angle, then, it will probably work ok?

I think the answer to this is definitively “no”. Under the right circumstances, even given the same scraper geometry as presented at the point-of-work, a regular scraper can self-feed while a negative rake scraper will resist that. Stu Batty does a great job of laying this out at the end of this Mid-Maryland Woodturners Club demo. Jump to the 1:37:00 mark to get to the relevant part.

tl;dw: While the geometry at the point-of-work for an NRS and a conventional scraper with the same bevel angles can be identical, the key difference is that the force of the tool-against-workpiece on a conventional scraper is always parallel to the bottom of the tool. I.e. the force pulls the tool into the workpiece through its axis. The tool rest provides NO support against this force, and handle leverage is negated

With a NRS, we can view the force at the tip of the tool as being split between forward and downward components, which occurs because of the tool’s top bevel. See Stu’s diagram in the video to visualize this change in direction of forces. The tool rest (and user control of the handle) can now provide support against the downward force, and the forward (self-feeding) force is reduced.

 

[Jon Rista]

I think the answer to this is definitively “no”. Under the right circumstances, even given the same scraper geometry as presented at the point-of-work, a regular scraper can self-feed while a negative rake scraper will resist that. Stu Batty does a great job of laying this out at the end of this Mid-Maryland Woodturners Club demo. Jump to the 1:37:00 mark to get to the relevant part.

tl;dw: While the geometry at the point-of-work for an NRS and a conventional scraper with the same bevel angles can be identical, the key difference is that the force of the tool-against-workpiece on a conventional scraper is always parallel to the bottom of the tool. I.e. the force pulls the tool into the workpiece through its axis. The tool rest provides NO support against this force, and handle leverage is negated

With a NRS, we can view the force at the tip of the tool as being split between forward and downward components, which occurs because of the tool’s top bevel. See Stu’s diagram in the video to visualize this change in direction of forces. The tool rest (and user control of the handle) can now provide support against the downward force, and the forward (self-feeding) force is reduced.

Well, its definitely "no" for me, at the very least. I stopped down angling my standard scrapers. I still use them strait in, but don't down angle them anymore. I all too frequently took nice bites out of my otherwise cleanly turned bowl innards by down angling.

I generally prefer NRS though. Just a lot easier and less risky for me.

 

[Bill Blasic]

Well Jon you have found your answer, just use your NRS. That is the answer for any tool, "Find What Works for You". When you have pros who have been turning for 30 years, some of which want you to buy their tools, say this is better than that. Well I just take that with a grain of salt as that does not mean it will work for me. Remember you are not one tool away from greatness. Greatness comes from practice, practice and practice.

 

[Tim Tucker]

One that understands the physics, and geometry of woodturning can quickly adapt to almost any tool. The argument about what is "best"....is just that. It is an argument. I say again the variables are too numerous to create a quantifiable, and qualified ..."best" that applies universally.

 

[John Whitley]

Well Jon you have found your answer, just use your NRS.

Sigh. Bill, I apologize if I came across as trying to Spread The Word of The NRS. But I've noted that there are a lot of turners who are competent enough to "know to hold the handle up" and who still say things like "I find the NRS to be less grabby than a conventional scraper". I find that interesting! There's another contingent of turners, faced with those statements who then say things like "the geometry is the same!" (between conventional and NRS), or just repeat "hold the handle up" over again... All this raised the question for me: is the difference "just" skill, or is there something else going on? Are there situations where the NRS has unique properties relative to a conventional scraper? Or is the NRS just "a crutch"?

To be clear, I'm absolutely not trying to imply that the tools in turner's hands, often for decades, don't work. (Nor will I argue here that water's not wet...) BUT... Stu's explanations which I linked above are, to date, the first and only clear exposition I've encountered of why, from a basic engineering-style forces view, NRS are actually different than conventional scrapers. He makes a throwaway comment in that video, to the effect of "shear scraping is negative rake scraping". This made no sense until I really got the diagrams he presented later. Rotating a conventional scraper changes the angle of the force at the nose of the scraper, increasing handle control and leverage in the same way as a negative rake scraper. What a delightful lightbulb moment! For me, that helps fit shear scraping into my range of techniques. What things to try, in what circumstances, perhaps with what wood is at hand.

Again, apologies if any of this offends you, but building this sort of understanding is pretty much how my brain works. And I likewise agree that none of it is a substitute for the learning that happens in the hands. Yet, I find the reverse is also very true: the learning in the hands has never been a substitute for learning to also think about the work (and real talk: figuring out why I just got that d*mn catch! )

 

[robo hippy]

Well, thinking about this all some more, one use I have for the NRS is in my recesses on my bowls. When using a NRS, you are just nibbling off the high spots until it smooths out. For a recess, I get less run out when I reverse the bowl than I do when I use a bevel rubbing cut with a gouge. When using scrapers on bowls, I am hogging off material as fast as possible, and these are two entirely different types of cuts. A shear scrape, similar to a NRS is about nibbling off the high spots. I also find these 2 cuts to be good for getting an almost perfectly round bowl. Try the "pencil test". After finish turning a bowl, put a pencil on it while it is spinning and see how complete of a circle you can get. I get much better results when I have finished the outside with a shear scrape or a NRS. Going for finish cuts with a gouge, even with my lightest touch, it seems that the gouge always bounces. I attribute this to the grain, up hill, down hill, up hill, down hill with each rotation. If you are turning at higher speeds, I figure the bowl will elongate a bit due to grain orientation also. Being able to have a light bevel rub helps. If you can make a pass down the outside or inside of a bowl, stop the cut, then resume it after repositioning your body and not have a bump, you are getting better....

robo hippy

 

[Jon Rista]

Well Jon you have found your answer, just use your NRS. That is the answer for any tool, "Find What Works for You". When you have pros who have been turning for 30 years, some of which want you to buy their tools, say this is better than that. Well I just take that with a grain of salt as that does not mean it will work for me. Remember you are not one tool away from greatness. Greatness comes from practice, practice and practice.

Bill, I am honestly not sure how the physics of a tilted standard scraper vs. a negative rake scraper held flat, has anything to do with "someone with 30 years of experience is trying to SELL YOU SOMETHING"... In all honesty, I am interested in what's actually effective, not what's best. I have five or six scrapers. A couple are still standard, others are NRS. I fully understand that there is not just one size fits all here.

I previously mentioned a Stuart Batty NRS that was $300, not because its an NRS, but because it will use 15V steel, which is ridiculously expensive. The prior discussion noted concerns that such steel is very brittle. I decided to reserve judgement until I read more and hear more about how they actually work in practice, before I reconsider buying one. FWIW, the replacement blades are around $80-$100, which is middling range for the cost of an entire replacement NRS scraper from other brands.

The recent discussion has been on the physics of NRS. That is not new, nor something someone with 30 years of experience told me to make a sale. I originally purchased NRS back in 2020, after reading a range of papers and web sites, and watching various videos. I recently reground an old, damaged round nose standard scraper to this (ended up with a long wing trying to grind an actual sharp edge on the side, was my first major regrind job, and that long wing will be diminished as I continue to sharpen this thing over time...its definitely too long. The shape will continue to be refined as well...I just needed an NRS as my standard scrapers keep running aground on the walls of smaller diameter bowls, usually burnishing the wood, which has been driving me crazy.)



But, oh, yeah, I really got duped with this one! SIXTY FIVE BIG ONES for this bad boy!! Hurricane, bad boys tryin to take your money!!

There ARE two forces involved when using a scraper. The force of the wood down on the tip of the scraper. The force of the scraper into the wood. A tilted standard scraper, does not involve the exact same forces as an NRS held flat. I'm educated well enough to understand the nature of a force vector, and I don't need anyone with 30 years or even 50 years of experience to tell me that. Further, I also have my own experiences, using standard and NRS scrapers generally strait in, and standard scrapers held at an angle so the flat top is presented negative to the wood. The latter, is an entirely different experience than the former two. Perhaps with another 25 years of experience with holding a scraper that way, I'll perfect it and avoid the inherent consequences of doing that...perhaps. However, managing the consequences does not eliminate them!

When I was reading about scrapers originally in 2020, I came across a lot of bad advice, too. There are many sources of information out there, that actually give TERRIBLE advice about scrapers and NRS in particular. Such as, the purpose of an NRS, is to eliminate the production of a burr, by explicitly using an included angle over 90 degrees. I actually tried that early on. Those scrapers never worked for me...they had basically no cutting power at all. What I did not know recently, was what were the optimal angles for top and bottom bevel, and I'm still going to have to experiment here, to find out which angles work best for me. The above is 50 degrees included, 25/25. Others have mentioned that having more metal below to hold a burr can be better for some cases. I will probably have to buy a new scraper to give that a try. I am still concerned about the bottom hitting the wall of the bowl, so I'll have to find a scraper with not as much thickness, I think...the one pictured above and two of my standard scrapers are all rather thick...

Anyway. The whole "find the tool that works for you"...that's a global copout, IMO. Its kind of a snarky way to say "I don't want to help you, figure out your own d*mn problems." If you don't want to participate or help, that's fine, but, if you do, then be helpful. There is a lot of knowledge to be had about hand tools. Its not about whats best "period", really, its about what works for what use cases, what steel is optimal for what use case, which steels will last long without degrading while turning (i.e. not too soft nor too hard, but maybe harder is better than soft in some cases), etc. I am still not convinced that just because 15V steel is more brittle, that it can't be viable or hold an edge longer for certain specific use cases. You say you would have to take what anyone with 30 years of experience and is selling you something with a grain of salt... What if you didn't have to? What if there was some community-sourced statistically sound information you could rely on, to help you understand the pros and cons of any given tool, for a variety of purposes? I never said I was looking for the "one tool to rule them all"... I said I wished there was some scientifically founded information that could help prospective tool buyers, buy the tools they need. Optimally, for the specific use cases they need a tool for.

Anyway...

 

[Jon Rista]

Sigh. Bill, I apologize if I came across as trying to Spread The Word of The NRS. But I've noted that there are a lot of turners who are competent enough to "know to hold the handle up" and who still say things like "I find the NRS to be less grabby than a conventional scraper". I find that interesting! There's another contingent of turners, faced with those statements who then say things like "the geometry is the same!" (between conventional and NRS), or just repeat "hold the handle up" over again... All this raised the question for me: is the difference "just" skill, or is there something else going on? Are there situations where the NRS has unique properties relative to a conventional scraper? Or is the NRS just "a crutch"?

To be clear, I'm absolutely not trying to imply that the tools in turner's hands, often for decades, don't work. (Nor will I argue here that water's not wet...) BUT... Stu's explanations which I linked above are, to date, the first and only clear exposition I've encountered of why, from a basic engineering-style forces view, NRS are actually different than conventional scrapers. He makes a throwaway comment in that video, to the effect of "shear scraping is negative rake scraping". This made no sense until I really got the diagrams he presented later. Rotating a conventional scraper changes the angle of the force at the nose of the scraper, increasing handle control and leverage in the same way as a negative rake scraper. What a delightful lightbulb moment! For me, that helps fit shear scraping into my range of techniques. What things to try, in what circumstances, perhaps with what wood is at hand.

Again, apologies if any of this offends you, but building this sort of understanding is pretty much how my brain works. And I likewise agree that none of it is a substitute for the learning that happens in the hands. Yet, I find the reverse is also very true: the learning in the hands has never been a substitute for learning to also think about the work (and real talk: figuring out why I just got that d*mn catch! )

Stu's explanations in that video you linked, were some of the most informative I've ever heard. Thankfully that video was one of the earlier videos I found, and I have tried to apply what I learned from that since mid to late 2020, not long after I first started turning. Just because someone sells something, doesn't mean their knowledge is only for the purposes of selling their wares. Batty knows what he knows because he had strong determination to learn these things himself, to turn better and turn faster.

Regarding NRS vs. down-tilted standard scraper. There is a lot more to it than just the angle of the tool and the two forces involved, right? When any scraper is held flat, you can swing it on the tool rest, without the angle of the tool as its presented to the wood having to change, right? Standard or NRS, when the tool is flat on the rest, then you can swing it side to side and the tool remains flat.

However, the moment you angle the tool down (or up, even), then the contact of the tool rest to the bottom of the tool, will force the angle of the tool as presented to teh wood, to change continually throughout the swing from say the center of the bowl to the rim. At the center, the angle of the cutting edge would be flat, horizontal, to the wood. But at the rim, so long as the entire flat bottom of the scraper is still fully on the tool rest, the angle of the cutting edge is actually at an angle to the wood as well, not just a downward angle, but also a SHEER angle...but kind of a backward sheer angle.

These photos are not good, was holding the tool with one hand and trying to photograph with the other. But trying to demonstrate here, that down-angling the tool has many additional complications compared to an NRS held flat on the rest and strait into the wood.

Down angle, center of bowl, flat on rest (no sheer orientation, its down but flat):


Down angle, rim of bowl, flat on rest (downward angled, but also a bit of a backwards sheer angle!):


Down angle, rim of bowl, corner on rest (angle is down, avoids a sheer orientation to the wood):



Note here, that when you try to maintain a downward angel, but avoid a sheer orientation, of the tool's edge at the wood, you have to lift one side of the tool, and leave only a corner of it on the rest (reduces stability):


(Apologies for the angles here. I would normally set the rest a bit farther back, so that the bevel of the tool was not on the rest. But I think the gist gets across.)

So its not just that you angle the tool down...the interface of the rest and the flat bottom of the tool, result in a continuously changing presentation of the cutting edge to the wood. I don't know how everyone handles that, but, to me, this presents challenges I have to overcome. If you do tilt the tool, so its resting on just a corner, that greatly reduces stability, and complicates using a downward angled scraper even more! It complicates the process of scraping. An NRS presented flat resolves those issues, while maintaining the benefit of the negative rake angle.

This is from my own experience, learned with my own hands. I used to use my standard scrapers in a negative, downward angled orientation, when the french curve NRS I was using (owned by someone else) was damaged. I thought it was the same, based on so many reports from a lot of turners that it is the same. But my own experiences tell me that down angling a standard scraper is quite different from using an NRS in a normal orientation. I still have and use standard scrapers. Sometimes I can't get a good angle in some parts of a bowl, to take off more wood, and a standard scraper can often be quite helpful there. I generally prefer an NRS though, for final cleanup of the wood surface. In either case, I hold them flat on the rest now most of the time. In some cases, I may angle a scraper up...but I guess when I do that, I'm explicitly looking to get that bit of sheer angle on the sides of the bowl...I guess that's something I learned from Richard Raffan, IIRC.

 

[Bob Vaughan]

Finally some good photos of action. Thank you Jon. That explains a lot about the tool edge profile in question.
So grind a stubby skew profile on the tip and leave the burr.

 

[Jon Rista]

Finally some good photos of action. Thank you Jon.

Yeah, sorry...I tried to explain that with words before, I should have just taken pictures earlier. Guess its true, a picture is worth a thousand words!

 

[Bob Vaughan]

So how much pressure does one use against the spinning wood?
Tough to describe the lightness.

Imagine you and your spouse are having an argument.
You know that you’ll lose but there are some points yet to be made.
There’s a distracting piece of lint or something on her cheek.

The amount of pressure needed to brush off the lint is about what one should use when shear scraping.

 

[robo hippy]

Carl Jacobs demonstrated for our club last night. He was showing now to use the brass insert rings for urns and boxes, which he sells. He had a bunch of NRSs from D Way. It appears that their "factory" grind is about 70+ on the bottom, and about 20 on the top. I did see some from Sorby which were supposed to be "hard wood" NRSs, and they appeared to be 80/20 or so, but REALLY blunt under angle.

As for pressure, it depends on what you are doing. With a NRS, quoting Tim/Tom Wirsing, can't remember.... "if you have to push at all to get shavings, then it is dull". If I am roughing, then I push as much as the lathe will take. I haven't met a lathe I can't stall yet. How much you can take off in one pass depends on horse power, and how big the tool you are using is/how big the cutting edge is. When starting out roughing any blank, I always start in the center since it is moving slower in feet/minute, so I can get a "feel" for the wood. I NEVER start on the outside edge of a blank where the wood is moving a lot faster, and it is generally more out of round. Too much potential for a big catch/taking too big of a bite. I never use scrapers wider than 1 inch. There is no need for more than that, and again, I can stall any lathe I have ever turned on with a 1 inch wide scraper. For shear scraping and NRSs, just a light brush against the wood. Some call it whisper cuts. These cuts are NOT for stock removal. They are only for final surfaces and cleaning up details. Same with final finish cuts with a gouge, higher rpms, and very slow feed rate, and VERY light pressure on the cut.

robo hippy

 

[Jon Rista]

I haven't done much roughing like Robo...most of my scraping has been for cleanup. I like the quote that if you have to push for shavings, then its dull. That is pretty much what I go by.

I've watched Richard Raffan turn entire boxes with nothing but scrapers. Its always been interesting to me, but, in the few cases I have tried, it always resulted in fairly significant tearout. Sure, it can be cleaned up, but, with more scraping just lighter cuts...but, I feel that tearout adds uncertainty. You don't necessarily know how deep it is, so you can't necessarily get exactly the wall thickness you want. At least, that's been my experience. So I went back to hogging out with gouges, then getting a finer surface with sheer scraping on the outside and normal scraping/NRS on the inside.

I am curious, how an 80/20 scraper works? I was under the impression that if the included angle is over 90° then you wouldn't get a burr nor much cutting ability...

 

[robo hippy]

There is a huge difference between cutting end grain like boxes and cutting side grain like bowls. I can get surfaces on my boxes that 400 grit roughs up. With bowls, since you cut into unsupported fibers, you always get tear out. Most of the time I use a shear scrape for my final cuts on bowls. I have been turning some California Bay Laurel lately that has been a royal pain. I changed forstner bits because the one I was using felt dull. The fresh bit still was sending up smoke. My Big Ugly tool was needing to be resharpened just about every other bowl rather than lasting for half a day before needing to be resharpened. Every log is different, and even pieces from the same log can be hugely different.

As for the Sorby 80/20 NRS, I think the included angle thing really is highly variable. They did call it a "hard wood" NRS. With dry wood, the harder it is, the cleaner the cuts from the NRS seem to be. I do prefer a burnished burr on my NRSs.

robo hippy

 

[John K Jordan]

I have been turning some California Bay Laurel lately that has been a royal pain. I changed forstner bits because the one I was using felt dull. The fresh bit still was sending up smoke.

Yikes. Your comment about forstner bits reminded me of something I came up with long ago that helped me when drilling.

I keep a compressed air nozzle at the lathe. When I drill with a forstner I direct a continuous stream of compressed air towards the back of the bit. This does two things: helps keep the chips cleared out, and cools the bit a little. Might not help with the Ca Bay Laurel but has helped with others, especially when drilling deep holes.

(You probably already know about and do this, but perhaps someone else reading might not have thought to try it.)

I've never seen any of that wood but the Wood Database reports it "Has a tendency to burn during drilling and routing" Ha!

Oregon myrtle | The Wood Database (Hardwood)

www.wood-database.com

Also, I keep sets of forstners carbide and steel (HSS?). The carbide don't make the sides of the holes as smooth but sure cut faster when smoothness doesn't matter.

JKJ

 

[Don Wattenhofer]

This is an example of shear scraping the inside of an end grain goblet with a single angle burred scraper. Notice the green arrow on the tool that indicates the portion of the edge doing the shear scraping also notice that the tool is not flat on the tool rest. It is all about presenting the burr in the best way to get the shearing action. The wood is some kind of ornamental cherry, I think.

 

[Jon Rista]

This is an example of shear scraping the inside of an end grain goblet with a single angle burred scraper. Notice the green arrow on the tool that indicates the portion of the edge doing the shear scraping also notice that the tool is not flat on the tool rest. It is all about presenting the burr in the best way to get the shearing action. The wood is some kind of ornamental cherry, I think.
View attachment 75802

I've sheer scraped like that before, for sure.

It looks like you are still effectively holding the tool "flat", even though its on a corner for sheer scraping. If that is the case, then your swing wouldn't encounter the constantly changing variable that is angle of the tool to the wood that I was trying to describe before. If you angle the tool down from the rest, then at the center of the bowl, the cutting edge is presented differently than at the rim, and over the length of the swing between the two, the orientation of that edge to the wood changes continually as you sweep.

If you hold the tool flat, even if you choose to use a sheer angle, the orientation of the cutting edge to the wood will remain the same throughout your sweep. IMO that's fine, and you are making a conscious choice to sheer scrape.

What I didn't like, when I used to angle the tool down, was that the orientation with a downward angle was always changing. Its another dynamic variable to account for, on top of the others that get added in when you down-angle the tool, and it just makes it harder.

 

[Bob Vaughan]

Awesome photo!
It really gets the point across.

 

[Gerald Lawrence]

Maybe someone could write a book on this subject so I can put it on the shelf. To me it is this works for me do what works for you? Not discounting all the methods and opinions on the subject but it does seem like beating a dead horse lately. I have one NRS at 70/25 and I love to use it . So what more could be proved if you are satisfied with your method?